1.React 前置知识 #

1.1 React 是什么? #

1.2 JSX 是什么 #

1.2.1 旧转换 #

1.2.1.1 jsx.js # 
const babel = require("@babel/core");
const sourceCode = `
<h1>
    hello<span style={{ color: "red" }}>world</span>
</h1>
`;
const result = babel.transform(sourceCode, {
  plugins: [["@babel/plugin-transform-react-jsx", { runtime: "classic" }]],
});
console.log(result.code);
1.2.1.2 转译结果 # 
React.createElement(
  "h1",
  null,
  "hello",
  React.createElement(
    "span",
    {
      style: {
        color: "red",
      },
    },
    "world"
  )
);

1.2.2 新转换 #

1.2.2.1 jsx.js # 
const babel = require("@babel/core");
const sourceCode = `
<h1>
    hello<span style={{ color: "red" }}>world</span>
</h1>
`;
const result = babel.transform(sourceCode, {
+ plugins: [["@babel/plugin-transform-react-jsx", { runtime: "automatic" }]],
});
console.log(result.code);
1.2.2.2 转译结果 # 
var { jsxDEV } = require("react/jsx-dev-runtime");
jsxDEV("h1", {
  children: [
    "hello",
    jsxDEV("span", {
      style: {
        color: "red",
      },
      children: "world",
    }),
  ],
});

1.3 Virtual DOM #

1.4 链表 #

1.4.1 链表分类 #

1.4.1.1 单向链表 #

1.4.1.2 双向链表 #

1.4.1.3 循环链表 #

1.4.1.4 示例 # 
const UpdateState = 0;
function initializeUpdateQueue(fiber) {
  const queue = {
    shared: {
      pending: null,
    },
  };
  fiber.updateQueue = queue;
}
function createUpdate() {
  const update = { tag: UpdateState };
  return update;
}
function enqueueUpdate(fiber, update) {
  const updateQueue = fiber.updateQueue;
  const sharedQueue = updateQueue.shared;
  const pending = sharedQueue.pending;
  if (pending === null) {
    update.next = update;
  } else {
    update.next = pending.next;
    pending.next = update;
  }
  updateQueue.shared.pending = update;
}
function getStateFromUpdate(update, prevState) {
  switch (update.tag) {
    case UpdateState: {
      const { payload } = update;
      const partialState = payload;
      return Object.assign({}, prevState, partialState);
    }
    default:
      return prevState;
  }
}
function processUpdateQueue(workInProgress) {
  const queue = workInProgress.updateQueue;
  const pendingQueue = queue.shared.pending;
  if (pendingQueue !== null) {
    queue.shared.pending = null;
    const lastPendingUpdate = pendingQueue;
    const firstPendingUpdate = lastPendingUpdate.next;
    lastPendingUpdate.next = null;
    let newState = workInProgress.memoizedState;
    let update = firstPendingUpdate;
    while (update) {
      newState = getStateFromUpdate(update, newState);
      update = update.next;
    }
    workInProgress.memoizedState = newState;
  }
}
let fiber = { memoizedState: { id: 1 } };
initializeUpdateQueue(fiber);
let update1 = createUpdate();
update1.payload = { name: "zhufeng" };
enqueueUpdate(fiber, update1);
let update2 = createUpdate();
update2.payload = { age: 14 };
enqueueUpdate(fiber, update2);
processUpdateQueue(fiber);
console.log(fiber);

1.5 fiber #

1.5.1 性能瓶颈 #

1.5.2 屏幕刷新率 #

1.5.3 帧 #

lifeofframe

1.5.4 requestIdleCallback #

cooperativescheduling2

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  </head>
  <body>
    <script>
      function sleep(d) {
        for (var t = Date.now(); Date.now() - t <= d; );
      }
      const works = [
        () => {
          console.log("第1个任务开始");
          sleep(20); //sleep(20);
          console.log("第1个任务结束");
        },
        () => {
          console.log("第2个任务开始");
          sleep(20); //sleep(20);
          console.log("第2个任务结束");
        },
        () => {
          console.log("第3个任务开始");
          sleep(20); //sleep(20);
          console.log("第3个任务结束");
        },
      ];

      requestIdleCallback(workLoop);
      function workLoop(deadline) {
        console.log("本帧剩余时间", parseInt(deadline.timeRemaining()));
        while (deadline.timeRemaining() > 1 && works.length > 0) {
          performUnitOfWork();
        }
        if (works.length > 0) {
          console.log(`只剩下${parseInt(deadline.timeRemaining())}ms,时间片到了等待下次空闲时间的调度`);
          requestIdleCallback(workLoop);
        }
      }
      function performUnitOfWork() {
        works.shift()();
      }
    </script>
  </body>
</html>

1.5.5 fiber #

1.5.5.1 Fiber 是一个执行单元 #

fiberflow

1.5.5.2 Fiber 是一种数据结构 #

1.5.5.3 递归构建 fiber 树 #

1.6 树的遍历 #

1.6.1 深度优先(DFS) # 

function dfs(node) {
  console.log(node.name);
  node.children &&
    node.children.forEach((child) => {
      dfs(child);
    });
}
let root = {
  name: "A",
  children: [
    {
      name: "B",
      children: [{ name: "B1" }, { name: "B2" }],
    },
    {
      name: "C",
      children: [{ name: "C1" }, { name: "C2" }],
    },
  ],
};
dfs(root);

1.6.2 广度优先(BFS) # 

function bfs(node) {
  const stack = [];
  stack.push(node);
  let current;
  while ((current = stack.shift())) {
    console.log(current.name);
    current.children &&
      current.children.forEach((child) => {
        stack.push(child);
      });
  }
}
let root = {
  name: "A",
  children: [
    {
      name: "B",
      children: [{ name: "B1" }, { name: "B2" }],
    },
    {
      name: "C",
      children: [{ name: "C1" }, { name: "C2" }],
    },
  ],
};
bfs(root);

1.6.3 栈 # 

class Stack {
  constructor() {
    this.data = [];
    this.top = 0;
  }
  push(node) {
    this.data[this.top++] = node;
  }
  pop() {
    return this.data[--this.top];
  }
  peek() {
    return this.data[this.top - 1];
  }
  size() {
    return this.top;
  }
  clear() {
    this.top = 0;
  }
}

const stack = new Stack();
stack.push("1");
stack.push("2");
stack.push("3");
console.log("stack.size()", stack.size());
console.log("stack.peek", stack.peek());
console.log("stack.pop()", stack.pop());
console.log("stack.peek()", stack.peek());
stack.push("4");
console.log("stack.peek", stack.peek());
stack.clear();
console.log("stack.size", stack.size());
stack.push("5");
console.log("stack.peek", stack.peek());

1.7 位运算 #

1.7.1 比特 #

bit

0b1000=2*2*2=Math.pow(2,3)=8

1.7.2 位运算 #

运算 使用 说明
按位与(&) x & y 每一个比特位都为 1 时，结果为 1，否则为 0
按位或() x y 每一个比特位都为 0 时，结果为 0，否则为 1

1.7.3 使用 # 

//定义常量
const Placement = 0b001; // 0b001
const Update = 0b010; // 0b010
//定义操作
let flags = 0b000;
//增加操作
flags |= Placement;
flags |= Update;
console.log(flags.toString(2)); //0b11
//删除操作
flags = flags & ~Placement;
console.log(flags.toString(2)); //0b10
//判断包含
console.log((flags & Placement) === Placement);
console.log((flags & Update) === Update);
//判断不包含
console.log((flags & Placement) === 0);
console.log((flags & Update) === 0);

1.8 事件 #

1.8.1 DOM 事件流 #

eventflow

1.8.2 事件捕获 #

1.8.3 目标阶段 # 

//w3c浏览器：event.target
//IE6、7、8： event.srcElement
let target = event.target || event.srcElement;

1.8.4 事件冒泡 #

1.8.5 addEventListener # 

element.addEventListener(event, function, useCapture)

1.8.6 阻止冒泡 # 

function stopPropagation(event) {
  if (!event) {
    window.event.cancelBubble = true;
  }
  if (event.stopPropagation) {
    event.stopPropagation();
  }
}

1.8.7 阻止默认行为 # 

function preventDefault(event) {
  if (!event) {
    window.event.returnValue = false;
  }
  if (event.preventDefault) {
    event.preventDefault();
  }
}

1.8.8 事件代理 # 

<body>
  <ul id="list" onclick="show(event)">
    <li>item 1</li>
    <li>item 2</li>
    <li>item 3</li>
    <li>item n</li>
  </ul>
  <script>
    function show(event) {
      alert(event.target.innerHTML);
    }
  </script>
</body>

1.8.9 事件系统 #

1.8.10.1 使用 #

eventuse

import * as React from "react";
import * as ReactDOM from "react-dom";
class App extends React.Component {
  parentRef = React.createRef();
  childRef = React.createRef();
  componentDidMount() {
    this.parentRef.current.addEventListener(
      "click",
      () => {
        console.log("父元素原生捕获");
      },
      true
    );
    this.parentRef.current.addEventListener("click", () => {
      console.log("父元素原生冒泡");
    });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log("子元素原生捕获");
      },
      true
    );
    this.childRef.current.addEventListener("click", () => {
      console.log("子元素原生冒泡");
    });
    document.addEventListener(
      "click",
      () => {
        console.log("document原生捕获");
      },
      true
    );
    document.addEventListener("click", () => {
      console.log("document原生冒泡");
    });
  }
  parentBubble = () => {
    console.log("父元素React事件冒泡");
  };
  childBubble = () => {
    console.log("子元素React事件冒泡");
  };
  parentCapture = () => {
    console.log("父元素React事件捕获");
  };
  childCapture = () => {
    console.log("子元素React事件捕获");
  };
  render() {
    return (
      <div ref={this.parentRef} onClick={this.parentBubble} onClickCapture={this.parentCapture}>
        <p ref={this.childRef} onClick={this.childBubble} onClickCapture={this.childCapture}>
          事件执行顺序
        </p>
      </div>
    );
  }
}
ReactDOM.render(<App />, document.getElementById("root"));
/**
document原生捕获
父元素React事件捕获
子元素React事件捕获
父元素原生捕获
子元素原生捕获
子元素原生冒泡
父元素原生冒泡
子元素React事件冒泡
父元素React事件冒泡
document原生冒泡
 */
1.8.10.2 简易实现 # 
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>event</title>
  </head>
  <body>
    <div id="root">
      <div id="parent">
        <div id="child">点击</div>
      </div>
    </div>
    <script>
      let root = document.getElementById("root");
      let parent = document.getElementById("parent");
      let child = document.getElementById("child");
      //listenToNativeEvent('click',false,root);
      //listenToNativeEvent( 'click',true,root);

      //root的捕获阶段的处理函数
      root.addEventListener("click", (event) => dispatchEvent(event, true), true);
      //root的冒泡阶段的处理函数
      root.addEventListener("click", (event) => dispatchEvent(event, false), false);
      function dispatchEvent(event, isCapture) {
        //console.log(event,isCapture);
        let paths = []; //事件的传播路径数组[child,parent,root,body,document]
        let currentTarget = event.target; //事件源
        while (currentTarget) {
          paths.push(currentTarget);
          currentTarget = currentTarget.parentNode;
        }
        if (isCapture) {
          //如果当前是捕获阶段
          for (let i = paths.length - 1; i >= 0; i--) {
            //[document,body,root,parent.child]
            let handler = paths[i].onClickCapture; //react捕获事件
            handler && handler();
          }
        } else {
          for (let i = 0; i < paths.length; i++) {
            //[child,parent,root,body,document]
            let handler = paths[i].onClick; //react冒泡事件
            handler && handler();
          }
        }
      }
      root.addEventListener("click", (event) => console.log("根元素原生事件捕获"), true);
      root.addEventListener("click", (event) => console.log("根元素原生事件冒泡"), false);
      parent.addEventListener(
        "click",
        () => {
          console.log("父元素原生事件捕获");
        },
        true
      );
      parent.addEventListener(
        "click",
        () => {
          console.log("父元素原生事件冒泡");
        },
        false
      );
      child.addEventListener(
        "click",
        () => {
          console.log("子元素原生事件捕获");
        },
        true
      );
      child.addEventListener(
        "click",
        () => {
          console.log("子元素原生事件冒泡");
        },
        false
      );
      parent.onClick = () => {
        console.log("React:父元素React事件冒泡");
      };
      parent.onClickCapture = () => {
        console.log("React:父元素React事件捕获");
      };
      child.onClick = () => {
        console.log("React:子元素React事件冒泡");
      };
      child.onClickCapture = () => {
        console.log("React:子元素React事件捕获");
      };
    </script>
  </body>
</html>

1.9 最小堆 #

1.9.1 二叉树 #

1.9.2 满二叉树 #

1.9.3 完全二叉树 #

1.9.4 最小堆 #

1.9.5 SchedulerMinHeap.js #

react\packages\scheduler\src\SchedulerMinHeap.js

export function push(heap, node) {
  const index = heap.length;
  heap.push(node);
  siftUp(heap, node, index);
}
export function peek(heap) {
  const first = heap[0];
  return first === undefined ? null : first;
}
export function pop(heap) {
  const first = heap[0];
  if (first !== undefined) {
    const last = heap.pop();
    if (last !== first) {
      heap[0] = last;
      siftDown(heap, last, 0);
    }
    return first;
  } else {
    return null;
  }
}

function siftUp(heap, node, i) {
  let index = i;
  while (true) {
    const parentIndex = index - 1 >>> 1;
    const parent = heap[parentIndex];
    if (parent !== undefined && compare(parent, node) > 0) {
      heap[parentIndex] = node;
      heap[index] = parent;
      index = parentIndex;
    } else {

      return;
    }
  }
}

function siftDown(heap, node, i) {
  let index = i;
  const length = heap.length;
  while (index < length) {
    const leftIndex = (index + 1) * 2 - 1;
    const left = heap[leftIndex];
    const rightIndex = leftIndex + 1;
    const right = heap[rightIndex]; 
    if (left !== undefined && compare(left, node) < 0) {
      if (right !== undefined && compare(right, left) < 0) {
        heap[index] = right;
        heap[rightIndex] = node;
        index = rightIndex;
      } else {
        heap[index] = left;
        heap[leftIndex] = node;
        index = leftIndex;
      }
    } else if (right !== undefined && compare(right, node) < 0) {
      heap[index] = right;
      heap[rightIndex] = node;
      index = rightIndex;
    } else {
      return;
    }
  }
}

function compare(a, b) {
  const diff = a.sortIndex - b.sortIndex;
  return diff !== 0 ? diff : a.id - b.id;
}

const { push, pop, peek } = require('./SchedulerMinHeap');
let heap = [];
push(heap, { sortIndex: 1 });
push(heap, { sortIndex: 2 });
push(heap, { sortIndex: 3 });
console.log(peek(heap));
push(heap, { sortIndex: 4 });
push(heap, { sortIndex: 5 });
push(heap, { sortIndex: 6 });
push(heap, { sortIndex: 7 });
console.log(peek(heap));
pop(heap);
console.log(peek(heap));

1.10 MessageChannel # 

var channel = new MessageChannel();
//channel.port1
//channel.port2

var channel = new MessageChannel();
var port1 = channel.port1;
var port2 = channel.port2
port1.onmessage = function(event) {
    console.log("port1收到来自port2的数据：" + event.data);
}
port2.onmessage = function(event) {
    console.log("port2收到来自port1的数据：" + event.data);
}
port1.postMessage("发送给port2");
port2.postMessage("发送给port1");

1.11 二进制 #

1.11.1 ES5规范 #

1.11.2 真值 # 

+ 00000001 # +1
- 00000001 # -1

1.11.3 原码 # 

0 0000001 # +1
1 0000001 # -1

1.11.4 反码 # 

0 0000001 # +1
1 1111110 # -1

1.11.5 补码 # 

0 0000001 # +1
1 1111111 # -1

1.11.6 二进制数整数 #

1.11.7 ~非 # 

0b00000011
3
~0b00000011 =>  0b11111100
-4
(~0b00000011).toString();
'-4'
(~0b00000011).toString(2);
'-100'

求补码的真值
1 表示负号
剩下的 1111100 开始转换
1111100 减1
1111011 取反
0000100 4

1.11.8 getHighestPriorityLane # 

/**
 * 分离出所有比特位中最右边的1
 * 分离出最高优先级的车道
 * @param {*} lanes 车道
 * @returns 车道
 */
function getHighestPriorityLane(lanes) {
    return lanes & -lanes;
}

lanes=0b00001100=12
-lanes=-12
1
0001100
1110011
1110100
11110100
00001100

1.11.9 左移 # 

(0b00000010<<1).toString(2)

1.11.10 >> 有符号右移 # 

(-0b111>>1).toString(2) "-100"
-0b111 -7
100000111 原码
111111000 反码
111111001 补码
111111100

1
111111100
111111011
000000100
1000000100
-100
-4

1.11.11 >>>无符号右移 # 

(0b111>>>1).toString(2)
>>> "11"

(-0b111>>>1).toString(2)
>>> "1111111111111111111111111111100"

00000000000000000000000000000111
11111111111111111111111111111000
11111111111111111111111111111001
01111111111111111111111111111100
2147483644

1.12 更新优先级 #

1.12.1 lane # 

//一共有16种优先级
//同步优先级
const SyncLanePriority = 15;
const SyncBatchedLanePriority = 14;
//离散事件优先级
const InputDiscreteHydrationLanePriority = 13;
const InputDiscreteLanePriority = 12;
//连续事件优先级
const InputContinuousHydrationLanePriority = 11;
const InputContinuousLanePriority = 10;
//默认优先级
const DefaultHydrationLanePriority = 9;
const DefaultLanePriority = 8;
//渐变优先级
const TransitionHydrationPriority = 7;
const TransitionPriority = 6;
const RetryLanePriority = 5;
const SelectiveHydrationLanePriority = 4;
//空闲优先级
const IdleHydrationLanePriority = 3;
const IdleLanePriority = 2;
//离屏优先级
const OffscreenLanePriority = 1;
//未设置优先级
const NoLanePriority = 0;
/**
 * 一共有31条车道
 */
const TotalLanes = 31;
//没有车道，所有位都为0
const NoLanes = 0b0000000000000000000000000000000;
const NoLane = 0b0000000000000000000000000000000;
//同步车道，优先级最高
const SyncLane = 0b0000000000000000000000000000001;
const SyncBatchedLane = 0b0000000000000000000000000000010;
//离散用户交互车道 click
const InputDiscreteHydrationLane = 0b0000000000000000000000000000100;
const InputDiscreteLanes = 0b0000000000000000000000000011000;
//连续交互车道 mouseMove
const InputContinuousHydrationLane = 0b0000000000000000000000000100000;
const InputContinuousLanes = 0b0000000000000000000000011000000;
//默认车道
const DefaultHydrationLane = 0b0000000000000000000000100000000;
const DefaultLanes = 0b0000000000000000000111000000000;
//渐变车道
const TransitionHydrationLane = 0b0000000000000000001000000000000;
const TransitionLanes = 0b0000000001111111110000000000000;
//重试车道
const RetryLanes = 0b0000011110000000000000000000000;
const SomeRetryLane = 0b0000010000000000000000000000000;
//选择性水合车道
const SelectiveHydrationLane = 0b0000100000000000000000000000000;
//非空闲车道
const NonIdleLanes = 0b0000111111111111111111111111111;
const IdleHydrationLane = 0b0001000000000000000000000000000;
//空闲车道
const IdleLanes = 0b0110000000000000000000000000000;
//离屏车道
const OffscreenLane = 0b1000000000000000000000000000000;

/**
 * 分离出所有比特位中最右边的1
 * 分离出最高优先级的车道
 * @param {*} lanes 车道
 * @returns 车道
 */
function getHighestPriorityLane(lanes) {
    return lanes & -lanes;
}

//console.log(getHighestPriorityLane(InputDiscreteLanes));//8 0b1000
//console.log('0000000000000000000000000011000');
//console.log('1111111111111111111111111101000');

/**
 * 分离出所有比特位中最左边的1
 * 分离出最低优先级的车道
 * @param {*} lanes 车道
 * @returns 车道
 */
function getLowestPriorityLane(lanes) {
    const index = 31 - Math.clz32(lanes);
    return index < 0 ? NoLanes : 1 << index;
}
console.log(getLowestPriorityLane(InputDiscreteLanes));//16 0b10000
console.log('0000000000000000000000000011000');
console.log(Math.clz32(InputDiscreteLanes));//27
console.log(31 - Math.clz32(InputDiscreteLanes));//4

1.12.2 Hydration #




1.12.3 ReactFiberLane.js #

ReactFiberLane.js

const NoLanes = 0b00;
const NoLane = 0b00;
const SyncLane = 0b01;
const SyncBatchedLane = 0b10;
/**
 * 判断subset是不是set的子集
 * @param {*} set 
 * @param {*} subset 
 * @returns 
 */
function isSubsetOfLanes(set, subset) {
    return (set & subset) === subset;
}
/**
 * 合并两个车道
 * @param {*} a 
 * @param {*} b 
 * @returns 
 */
function mergeLanes(a, b) {
    return a | b;
}
module.exports = {
    NoLane,
    NoLanes,
    SyncLane,
    SyncBatchedLane,
    isSubsetOfLanes,
    mergeLanes
}

1.12.4 ReactUpdateQueue.js #

ReactUpdateQueue.js

const { NoLane, NoLanes, isSubsetOfLanes, mergeLanes } = require('./ReactFiberLane');
function initializeUpdateQueue(fiber) {
  const queue = {
    baseState: fiber.memoizedState,//本次更新前该Fiber节点的state,Update基于该state计算更新后的state
    firstBaseUpdate: null,//本次更新前该Fiber节点已保存的Update链表头
    lastBaseUpdate: null,//本次更新前该Fiber节点已保存的Update链表尾
    shared: {
      //触发更新时，产生的Update会保存在shared.pending中形成单向环状链表
      //当由Update计算state时这个环会被剪开并连接在lastBaseUpdate后面
      pending: null
    }
  }
  fiber.updateQueue = queue;
}
function enqueueUpdate(fiber, update) {
  const updateQueue = fiber.updateQueue;
  if (updateQueue === null) {
    return;
  }
  const sharedQueue = updateQueue.shared;
  const pending = sharedQueue.pending;
  if (pending === null) {
    update.next = update;
  } else {
    update.next = pending.next;
    pending.next = update;
  }
  sharedQueue.pending = update;
}

/**
 * 处理更新队列
 * @param {*} fiber 
 * @param {*} renderLanes 
 */
function processUpdateQueue(fiber, renderLanes) {
  //获取此fiber上的更新队列
  const queue = fiber.updateQueue;
  //获取第一个更新
  let firstBaseUpdate = queue.firstBaseUpdate;
  let lastBaseUpdate = queue.lastBaseUpdate;
  //判断一下是否在等待生效的的更新，如果有，变成base队列
  let pendingQueue = queue.shared.pending;
  if (pendingQueue !== null) {
    //等待生效的队列是循环队列
    queue.shared.pending = null;
    //最后一个等待的更新 update4
    const lastPendingUpdate = pendingQueue;
    //第一个等待的更新 update1
    const firstPendingUpdate = lastPendingUpdate.next;
    //把环剪断，最后一个不再指向第一个
    lastPendingUpdate.next = null;
    //把等待生效的队列添加到base队列中
    //如果base队列为空
    if (lastBaseUpdate === null) {
      firstBaseUpdate = firstPendingUpdate;
    } else {//否则就把当前的更新队列添加到base队列的尾部
      lastBaseUpdate.next = firstPendingUpdate;
    }
    //尾部也接上
    lastBaseUpdate = lastPendingUpdate;
  }
  //开始计算新的状态
  if (firstBaseUpdate !== null) {
    //先获取老的值{number:0}
    let newState = queue.baseState;
    let newLanes = NoLanes;
    let newBaseState = null;//新的基础状态
    let newFirstBaseUpdate = null;//第一个跳过的更新
    let newLastBaseUpdate = null;//新的最后一个基本更新
    let update = firstBaseUpdate;//指向第一个更新
    do {
      //获取更新车道
      const updateLane = update.lane;
      //如果优先级不够，跳过这个更新，如果这是第一个跳过的更新，上一个状态和更新成为newBaseState和newFirstBaseUpdate
      if (!isSubsetOfLanes(renderLanes, updateLane)) {
        const clone = {
          id: update.id,
          lane: updateLane,
          payload: update.payload
        };
        if (newLastBaseUpdate === null) {
          newFirstBaseUpdate = newLastBaseUpdate = clone;// first=last=update1
          newBaseState = newState;//0
        } else {
          newLastBaseUpdate = newLastBaseUpdate.next = clone;
        }
        //更新队列中的剩下的优先级
        newLanes = mergeLanes(newLanes, updateLane);
      } else {
        //如果有足够的优先级 如果有曾经跳过的更新，仍然追加在后面
        if (newLastBaseUpdate !== null) {
          const clone = {
            id: update.id,
            //NoLane是所有的优先级的子集，永远不会被跳过
            lane: NoLane,
            payload: update.payload
          };
          newLastBaseUpdate = newLastBaseUpdate.next = clone;
        }
        newState = getStateFromUpdate(update, newState);
      }
      update = update.next;
      if (!update) {
        break;
      }
    } while (true);

    if (!newLastBaseUpdate) {
      newBaseState = newState;
    }
    queue.baseState = newBaseState;
    queue.firstBaseUpdate = newFirstBaseUpdate;
    queue.lastBaseUpdate = newLastBaseUpdate;
    fiber.lanes = newLanes;
    fiber.memoizedState = newState;
  }
}

function getStateFromUpdate(update, prevState) {
  const payload = update.payload;
  let partialState = payload(prevState);
  return Object.assign({}, prevState, partialState);
}
module.exports = {
  initializeUpdateQueue,
  enqueueUpdate,
  processUpdateQueue
}

1.12.5 processUpdateQueue.js #

use.js

const { initializeUpdateQueue, enqueueUpdate, processUpdateQueue } = require('./ReactUpdateQueue');
const { SyncBatchedLane, SyncLane } = require('./ReactFiberLane');

//初始化fiber节点
let fiber = { memoizedState: { msg: '' } };
initializeUpdateQueue(fiber);
let update1 = { id: 'A', payload: (state) => ({ msg: state.msg + 'A' }), lane: SyncBatchedLane };
enqueueUpdate(fiber, update1);
let update2 = { id: 'B', payload: (state) => ({ msg: state.msg + 'B' }), lane: SyncLane };
enqueueUpdate(fiber, update2);
let update3 = { id: 'C', payload: (state) => ({ msg: state.msg + 'C' }), lane: SyncBatchedLane };
enqueueUpdate(fiber, update3);
let update4 = { id: 'D', payload: (state) => ({ msg: state.msg + 'D' }), lane: SyncLane };
enqueueUpdate(fiber, update4);

//以同步的优先级进行更新
processUpdateQueue(fiber, SyncLane);
console.log('memoizedState', fiber.memoizedState);
console.log('updateQueue', printQueue(fiber.updateQueue));

let update5 = { id: 'E', payload: (state) => ({ msg: state.msg + 'E' }), lane: SyncLane };
enqueueUpdate(fiber, update5);
processUpdateQueue(fiber, SyncLane);
console.log('memoizedState', fiber.memoizedState);
console.log('updateQueue', printQueue(fiber.updateQueue));

processUpdateQueue(fiber, SyncBatchedLane);
console.log('memoizedState', fiber.memoizedState);
console.log('updateQueue', printQueue(fiber.updateQueue));

let update6 = { id: 'F', payload: (state) => ({ msg: state.msg + 'F' }), lane: SyncLane };
enqueueUpdate(fiber, update6);
processUpdateQueue(fiber, SyncLane);
console.log('memoizedState', fiber.memoizedState);
console.log('updateQueue', printQueue(fiber.updateQueue));


function printQueue(queue) {
  const { baseState, firstBaseUpdate } = queue
  let state = baseState.msg + '|';
  let update = firstBaseUpdate;
  while (update) {
    state += ((update.id) + "=>");
    update = update.next;
  }
  state += "null";
  console.log(state);
}

2.创建项目 #

2.1 创建目录 # 

mkdir react182
cd react182
npm init -y

2.2 安装 # 

npm install vite @vitejs/plugin-react --save

2.3 vite.config.js # 

import { defineConfig } from "vite";
import react from "@vitejs/plugin-react";
import path from "path";

export default defineConfig({
  define: {
    __DEV__: true,
    __PROFILE__: true,
    __UMD__: true,
    __EXPERIMENTAL__: true,
  },
  resolve: {
    alias: {
      react: path.posix.resolve("src/react"),
      "react-dom": path.posix.resolve("src/react-dom"),
      "react-dom-bindings": path.posix.resolve("src/react-dom-bindings"),
      "react-reconciler": path.posix.resolve("src/react-reconciler"),
      scheduler: path.posix.resolve("src/scheduler"),
      shared: path.posix.resolve("src/shared"),
    },
  },
  plugins: [react()],
  optimizeDeps: {
    force: true,
  },
});

2.4 jsconfig.json #

jsconfig.json

{
  "compilerOptions": {
    "baseUrl": "./",
    "paths": {
      "react/*": ["src/react/*"],
      "react-dom/*": ["src/react-dom/*"],
      "react-dom-bindings/*": ["react-dom-bindings/*"],
      "react-reconciler/*": ["src/react-reconciler/*"],
      "scheduler/*": ["scheduler/*"],
      "shared/*": ["src/shared/*"]
    }
  },
  "exclude": ["node_modules", "dist"]
}

2.5 main.jsx #

src\main.jsx

console.log("main");

2.6 index.html #

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>React18</title>
  </head>

  <body>
    <div id="root"></div>
    <script type="module" src="/src/main.jsx"></script>
  </body>
</html>

2.7 package.json #

package.json

{
  "scripts": {
    "dev": "vite"
  }
}

3.实现虚拟 DOM #

3.1 main.jsx #

main.jsx

let element = (
  <h1>
    hello<span style={{ color: "red" }}>world</span>
  </h1>
);
console.log(element);

3.2 jsx-dev-runtime.js #

src\react\jsx-dev-runtime.js

export { jsxDEV } from "./src/jsx/ReactJSXElement";

3.3 ReactJSXElement.js #

src\react\src\jsx\ReactJSXElement.js

import hasOwnProperty from "shared/hasOwnProperty";
import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";

const RESERVED_PROPS = {
  key: true,
  ref: true,
  __self: true,
  __source: true,
};
function hasValidRef(config) {
  return config.ref !== undefined;
}

const ReactElement = (type, key, ref, props) => {
  const element = {
    $$typeof: REACT_ELEMENT_TYPE,
    type,
    key,
    ref,
    props,
  };
  return element;
};

export function jsxDEV(type, config, maybeKey) {
  let propName;
  const props = {};
  let key = null;
  let ref = null;

  if (maybeKey !== undefined) {
    key = "" + maybeKey;
  }

  if (hasValidRef(config)) {
    ref = config.ref;
  }

  for (propName in config) {
    if (hasOwnProperty.call(config, propName) && !RESERVED_PROPS.hasOwnProperty(propName)) {
      props[propName] = config[propName];
    }
  }
  return ReactElement(type, key, ref, props);
}

3.4 ReactSymbols.js #

src\shared\ReactSymbols.js

export const REACT_ELEMENT_TYPE = Symbol.for("react.element");

3.5 hasOwnProperty.js #

src\shared\hasOwnProperty.js

const { hasOwnProperty } = Object.prototype;
export default hasOwnProperty;

4.创建 ReactDOMRoot #

4.1 main.jsx #

src\main.jsx

+import { createRoot } from "react-dom/client";
let element = (
  <h1>
    hello<span style={{ color: "red" }}>world</span>
  </h1>
);
+const root = createRoot(document.getElementById("root"));
+console.log(root);

4.2 client.js #

src\react-dom\client.js

export { createRoot } from "./src/client/ReactDOMRoot";

4.3 ReactDOMRoot.js #

src\react-dom\src\client\ReactDOMRoot.js

import { createContainer } from "react-reconciler/src/ReactFiberReconciler";

function ReactDOMRoot(internalRoot) {
  this._internalRoot = internalRoot;
}

export function createRoot(container) {
  const root = createContainer(container);
  return new ReactDOMRoot(root);
}

4.4 ReactFiberReconciler.js #

src\react-reconciler\src\ReactFiberReconciler.js

import { createFiberRoot } from "./ReactFiberRoot";
export function createContainer(containerInfo) {
  return createFiberRoot(containerInfo);
}

4.5 ReactFiberRoot.js #

src\react-reconciler\src\ReactFiberRoot.js

function FiberRootNode(containerInfo) {
  this.containerInfo = containerInfo;
}

export function createFiberRoot(containerInfo) {
  const root = new FiberRootNode(containerInfo);
  return root;
}

5.创建 RootFiber #

5.1 ReactFiberRoot.js #

src\react-reconciler\src\ReactFiberRoot.js

+import { createHostRootFiber } from "./ReactFiber";
function FiberRootNode(containerInfo) {
  this.containerInfo = containerInfo;
}

export function createFiberRoot(containerInfo) {
  const root = new FiberRootNode(containerInfo);
+ const uninitializedFiber = createHostRootFiber();
+ root.current = uninitializedFiber;
+ uninitializedFiber.stateNode = root;
  return root;
}

5.2 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

import { HostRoot } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.alternate = null;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}

5.3 ReactWorkTags.js #

src\react-reconciler\src\ReactWorkTags.js

export const HostRoot = 3;

5.4 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;

6.初始化 UpdateQueue #

6.1 ReactFiberRoot.js #

src\react-reconciler\src\ReactFiberRoot.js

import { createHostRootFiber } from "./ReactFiber";
+import { initializeUpdateQueue } from "./ReactFiberClassUpdateQueue";
function FiberRootNode(containerInfo) {
  this.containerInfo = containerInfo;
}

export function createFiberRoot(containerInfo) {
  const root = new FiberRootNode(containerInfo);
  const uninitializedFiber = createHostRootFiber();
  root.current = uninitializedFiber;
  uninitializedFiber.stateNode = root;
+ initializeUpdateQueue(uninitializedFiber);
  return root;
}

6.2 ReactFiberClassUpdateQueue.js #

src\react-reconciler\src\ReactFiberClassUpdateQueue.js

export function initializeUpdateQueue(fiber) {
  const queue = {
    shared: {
      pending: null,
    },
  };
  fiber.updateQueue = queue;
}

7. enqueueUpdate #

7.1 main.jsx #

src\main.jsx

import { createRoot } from "react-dom/client";
let element = (
  <h1>
    hello<span style={{ color: "red" }}>world</span>
  </h1>
);
const root = createRoot(document.getElementById("root"));
+root.render(element);

7.2 ReactDOMRoot.js #

src\react-dom\src\client\ReactDOMRoot.js

import {
  createContainer,
+ updateContainer,
} from "react-reconciler/src/ReactFiberReconciler";

function ReactDOMRoot(internalRoot) {
  this._internalRoot = internalRoot;
}
+ReactDOMRoot.prototype.render = function render(children) {
+  const root = this._internalRoot;
+  root.containerInfo.innerHTML = "";
+  updateContainer(children, root);
+};
export function createRoot(container) {
  const root = createContainer(container);
  return new ReactDOMRoot(root);
}

7.3 ReactFiberReconciler.js #

src\react-reconciler\src\ReactFiberReconciler.js

import { createFiberRoot } from "./ReactFiberRoot";
+import { createUpdate, enqueueUpdate } from "./ReactFiberClassUpdateQueue";
export function createContainer(containerInfo) {
  return createFiberRoot(containerInfo);
}
+export function updateContainer(element, container) {
+  const current = container.current;
+  const update = createUpdate();
+  update.payload = { element };
+  const root = enqueueUpdate(current, update);
+  console.log(root);
+}

7.4 ReactFiberClassUpdateQueue.js #

src\react-reconciler\src\ReactFiberClassUpdateQueue.js

+import { markUpdateLaneFromFiberToRoot } from "./ReactFiberConcurrentUpdates";
+export const UpdateState = 0;
export function initializeUpdateQueue(fiber) {
  const queue = {
    shared: {
      pending: null,
    },
  };
  fiber.updateQueue = queue;
}
+export function createUpdate() {
+  const update = { tag: UpdateState };
+  return update;
+}
+export function enqueueUpdate(fiber, update) {
+  const updateQueue = fiber.updateQueue;
+  const sharedQueue = updateQueue.shared;
+  const pending = sharedQueue.pending;
+  if (pending === null) {
+    update.next = update;
+  } else {
+    update.next = pending.next;
+    pending.next = update;
+  }
+  updateQueue.shared.pending = update;
+  return markUpdateLaneFromFiberToRoot(fiber);
+}

7.5 ReactFiberConcurrentUpdates.js #

src\react-reconciler\src\ReactFiberConcurrentUpdates.js

import { HostRoot } from "./ReactWorkTags";
export function markUpdateLaneFromFiberToRoot(sourceFiber) {
  let node = sourceFiber;
  let parent = sourceFiber.return;
  while (parent !== null) {
    node = parent;
    parent = parent.return;
  }
  if (node.tag === HostRoot) {
    const root = node.stateNode;
    return root;
  }
  return null;
}

8.performConcurrentWorkOnRoot #

8.1 ReactFiberReconciler.js #

src\react-reconciler\src\ReactFiberReconciler.js

import { createFiberRoot } from "./ReactFiberRoot";
import { createUpdate, enqueueUpdate } from "./ReactFiberClassUpdateQueue";
+import { scheduleUpdateOnFiber } from "./ReactFiberWorkLoop";
export function createContainer(containerInfo) {
  return createFiberRoot(containerInfo);
}
export function updateContainer(element, container) {
  const current = container.current;
  const update = createUpdate();
  update.payload = { element };
  const root = enqueueUpdate(current, update);
+ scheduleUpdateOnFiber(root);
}

8.2 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  console.log("performConcurrentWorkOnRoot");
}

8.3 scheduler\index.js #

src\scheduler\index.js

export * from "./src/forks/Scheduler";

8.4 Scheduler.js #

src\scheduler\src\forks\Scheduler.js

export function scheduleCallback(callback) {
  requestIdleCallback(callback);
}

9.prepareFreshStack #

9.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
+import { createWorkInProgress } from "./ReactFiber";
+let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
+ renderRootSync(root);
}
+function prepareFreshStack(root) {
+  workInProgress = createWorkInProgress(root.current, null);
+  console.log(workInProgress);
+}
+function renderRootSync(root) {
+  prepareFreshStack(root);
+}

9.2 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

import { HostRoot } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.alternate = null;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}
+// We use a double buffering pooling technique because we know that we'll
+// only ever need at most two versions of a tree. We pool the "other" unused
+// node that we're free to reuse. This is lazily created to avoid allocating
+// extra objects for things that are never updated. It also allow us to
+// reclaim the extra memory if needed.
+//我们使用双缓冲池技术，因为我们知道一棵树最多只需要两个版本
+//我们将“其他”未使用的我们可以自由重用的节点
+//这是延迟创建的，以避免分配从未更新的内容的额外对象。它还允许我们如果需要，回收额外的内+存
+export function createWorkInProgress(current, pendingProps) {
+  let workInProgress = current.alternate;
+  if (workInProgress === null) {
+    workInProgress = createFiber(current.tag, pendingProps, current.key);
+    workInProgress.type = current.type;
+    workInProgress.stateNode = current.stateNode;
+    workInProgress.alternate = current;
+    current.alternate = workInProgress;
+  } else {
+    workInProgress.pendingProps = pendingProps;
+    workInProgress.type = current.type;
+    workInProgress.flags = NoFlags;
+    workInProgress.subtreeFlags = NoFlags;
+  }
+  workInProgress.child = current.child;
+  workInProgress.memoizedProps = current.memoizedProps;
+  workInProgress.memoizedState = current.memoizedState;
+  workInProgress.updateQueue = current.updateQueue;
+  workInProgress.sibling = current.sibling;
+  workInProgress.index = current.index;
+  return workInProgress;
+}

10.beginWork #

10.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);

}
function renderRootSync(root) {
  prepareFreshStack(root);
+ workLoopSync();
}

+function workLoopSync() {
+  while (workInProgress !== null) {
+    performUnitOfWork(workInProgress);
+  }
+}
+function performUnitOfWork(unitOfWork) {
+  const current = unitOfWork.alternate;
+  const next = beginWork(current, unitOfWork);
+  unitOfWork.memoizedProps = unitOfWork.pendingProps;
+  if (next === null) {
+    //completeUnitOfWork(unitOfWork);
+    workInProgress = null;
+  } else {
+    workInProgress = next;
+  }
+}

10.2 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import { HostRoot, HostComponent, HostText } from "./ReactWorkTags";
import { processUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import logger, { indent } from "shared/logger";
function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(workInProgress, current.child, nextChildren);
  }
}
function updateHostRoot(current, workInProgress) {
  processUpdateQueue(workInProgress);
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
export function beginWork(current, workInProgress) {
  logger(" ".repeat(indent.number) + "beginWork", workInProgress);
  switch (workInProgress.tag) {
    case HostRoot:
      return updateHostRoot(current, workInProgress);
    case HostComponent:
      return updateHostComponent(current, workInProgress);
    case HostText:
    default:
      return null;
  }
}

10.3 ReactWorkTags.js #

src\react-reconciler\src\ReactWorkTags.js

export const HostRoot = 3;
+export const IndeterminateComponent = 2;
+export const HostComponent = 5;
+export const HostText = 6;

10.4 ReactFiberClassUpdateQueue.js #

src\react-reconciler\src\ReactFiberClassUpdateQueue.js

import { markUpdateLaneFromFiberToRoot } from "./ReactFiberConcurrentUpdates";
+import assign from "shared/assign";
export const UpdateState = 0;
export function initializeUpdateQueue(fiber) {
  const queue = {
    shared: {
      pending: null,
    },
  };
  fiber.updateQueue = queue;
}
export function createUpdate() {
  const update = { tag: UpdateState };
  return update;
}
export function enqueueUpdate(fiber, update) {
  const updateQueue = fiber.updateQueue;
  const sharedQueue = updateQueue.shared;
  const pending = sharedQueue.pending;
  if (pending === null) {
    update.next = update;
  } else {
    update.next = pending.next;
    pending.next = update;
  }
  updateQueue.shared.pending = update;
  return markUpdateLaneFromFiberToRoot(fiber);
}

+function getStateFromUpdate(update, prevState) {
+  switch (update.tag) {
+    case UpdateState: {
+      const { payload } = update;
+      const partialState = payload;
+      return assign({}, prevState, partialState);
+    }
+    default:
+      return prevState;
+  }
+}
+export function processUpdateQueue(workInProgress) {
+  const queue = workInProgress.updateQueue;
+  const pendingQueue = queue.shared.pending;
+  if (pendingQueue !== null) {
+    queue.shared.pending = null;
+    const lastPendingUpdate = pendingQueue;
+    const firstPendingUpdate = lastPendingUpdate.next;
+    lastPendingUpdate.next = null;
+    let newState = workInProgress.memoizedState;
+    let update = firstPendingUpdate;
+    while (update) {
+      newState = getStateFromUpdate(update, newState);
+      update = update.next;
+    }
+    workInProgress.memoizedState = newState;
+  }
+}

10.5 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText } from "./ReactFiber";
import { Placement } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects) newFiber.flags |= Placement;
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, newIndex) {
    newFiber.index = newIndex;
    if (shouldTrackSideEffects) newFiber.flags |= Placement;
  }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    for (; newIdx < newChildren.length; newIdx++) {
      const newFiber = createChild(returnFiber, newChildren[newIdx]);
      if (newFiber === null) {
        continue;
      }
      placeChild(newFiber, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
    }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

10.6 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

export function shouldSetTextContent(type, props) {
  return typeof props.children === "string" || typeof props.children === "number";
}

10.7 logger.js #

src\shared\logger.js

import * as ReactWorkTags from "react-reconciler/src/ReactWorkTags";
const ReactWorkTagsMap = new Map();
for (let tag in ReactWorkTags) {
  ReactWorkTagsMap.set(ReactWorkTags[tag], tag);
}

export default function logger(prefix, workInProgress) {
  let tagValue = workInProgress.tag;
  let tagName = ReactWorkTagsMap.get(tagValue);
  let str = ` ${tagName} `;
  if (tagName === "HostComponent") {
    str += ` ${workInProgress.type} `;
  } else if (tagName === "HostText") {
    str += ` ${workInProgress.pendingProps} `;
  }
  console.log(`${prefix} ${str}`);
}

let indent = { number: 0 };
export { indent };

10.8 assign.js #

src\shared\assign.js

const { assign } = Object;
export default assign;

10.9 isArray.js #

src\shared\isArray.js

const { isArray } = Array;
export default isArray;

10.10 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

import {
  HostRoot,
+ IndeterminateComponent,
+ HostComponent,
+ HostText,
} from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.alternate = null;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}
// We use a double buffering pooling technique because we know that we'll
// only ever need at most two versions of a tree. We pool the "other" unused
// node that we're free to reuse. This is lazily created to avoid allocating
// extra objects for things that are never updated. It also allow us to
// reclaim the extra memory if needed.
//我们使用双缓冲池技术，因为我们知道一棵树最多只需要两个版本
//我们将“其他”未使用的我们可以自由重用的节点
//这是延迟创建的，以避免分配从未更新的内容的额外对象。它还允许我们如果需要，回收额外的内存
export function createWorkInProgress(current, pendingProps) {
  let workInProgress = current.alternate;
  if (workInProgress === null) {
    workInProgress = createFiber(current.tag, pendingProps, current.key);
    workInProgress.type = current.type;
    workInProgress.stateNode = current.stateNode;
    workInProgress.alternate = current;
    current.alternate = workInProgress;
  } else {
    workInProgress.pendingProps = pendingProps;
    workInProgress.type = current.type;
    workInProgress.flags = NoFlags;
    workInProgress.subtreeFlags = NoFlags;
  }
  workInProgress.child = current.child;
  workInProgress.memoizedProps = current.memoizedProps;
  workInProgress.memoizedState = current.memoizedState;
  workInProgress.updateQueue = current.updateQueue;
  workInProgress.sibling = current.sibling;
  workInProgress.index = current.index;
  return workInProgress;
}
+export function createFiberFromTypeAndProps(type, key, pendingProps) {
+  let fiberTag = IndeterminateComponent;
+  if (typeof type === "string") {
+    fiberTag = HostComponent;
+  }
+  const fiber = createFiber(fiberTag, pendingProps, key);
+  fiber.type = type;
+  return fiber;
+}
+export function createFiberFromElement(element) {
+  const { type } = element;
+  const { key } = element;
+  const pendingProps = element.props;
+  const fiber = createFiberFromTypeAndProps(type, key, pendingProps);
+  return fiber;
+}
+
+export function createFiberFromText(content) {
+  const fiber = createFiber(HostText, content, null);
+  return fiber;
+}

10.11 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
+export const Placement = 0b00000000000000000000000010;
+export const MutationMask = Placement;

11.completeUnitOfWork #

11.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
+import { completeWork } from "./ReactFiberCompleteWork";
let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
+   completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

+function completeUnitOfWork(unitOfWork) {
+  let completedWork = unitOfWork;
+  do {
+    const current = completedWork.alternate;
+    const returnFiber = completedWork.return;
+    completeWork(current, completedWork);
+    const siblingFiber = completedWork.sibling;
+    if (siblingFiber !== null) {
+      workInProgress = siblingFiber;
+      return;
+    }
+    completedWork = returnFiber;
+    workInProgress = completedWork;
+  } while (completedWork !== null);
+}

11.2 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HostComponent, HostRoot, HostText } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
import logger, { indent } from "shared/logger";
function bubbleProperties(completedWork) {
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}

export function completeWork(current, workInProgress) {
  indent.number -= 2;
  logger(" ".repeat(indent.number) + "completeWork", workInProgress);
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
      const instance = createInstance(type, newProps, workInProgress);
      appendAllChildren(instance, workInProgress);
      workInProgress.stateNode = instance;
      finalizeInitialChildren(instance, type, newProps);
      bubbleProperties(workInProgress);
      break;
    }
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
    default:
      break;
  }
}

11.3 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

+import { setInitialProperties } from "./ReactDOMComponent";
export function shouldSetTextContent(type, props) {
  return (
    typeof props.children === "string" || typeof props.children === "number"
  );
}
+export const appendInitialChild = (parent, child) => {
+  parent.appendChild(child);
+};
+export const createInstance = (type, props, internalInstanceHandle) => {
+  const domElement = document.createElement(type);
+  return domElement;
+};
+export const createTextInstance = (content) => document.createTextNode+(content);
+export function finalizeInitialChildren(domElement, type, props) {
+  setInitialProperties(domElement, type, props);
+}

11.4 ReactDOMComponent.js #

src\react-dom-bindings\src\client\ReactDOMComponent.js

import { setValueForStyles } from "./CSSPropertyOperations";
import setTextContent from "./setTextContent";
import { setValueForProperty } from "./DOMPropertyOperations";
const CHILDREN = "children";
const STYLE = "style";
function setInitialDOMProperties(tag, domElement, nextProps) {
  for (const propKey in nextProps) {
    if (nextProps.hasOwnProperty(propKey)) {
      const nextProp = nextProps[propKey];
      if (propKey === STYLE) {
        setValueForStyles(domElement, nextProp);
      } else if (propKey === CHILDREN) {
        if (typeof nextProp === "string") {
          setTextContent(domElement, nextProp);
        } else if (typeof nextProp === "number") {
          setTextContent(domElement, `${nextProp}`);
        }
      } else if (nextProp != null) {
        setValueForProperty(domElement, propKey, nextProp);
      }
    }
  }
}
export function setInitialProperties(domElement, tag, props) {
  setInitialDOMProperties(tag, domElement, props);
}

11.5 CSSPropertyOperations.js #

src\react-dom-bindings\src\client\CSSPropertyOperations.js

export function setValueForStyles(node, styles) {
  const { style } = node;
  for (const styleName in styles) {
    if (styles.hasOwnProperty(styleName)) {
      const styleValue = styles[styleName];
      style[styleName] = styleValue;
    }
  }
}

11.6 setTextContent.js #

src\react-dom-bindings\src\client\setTextContent.js

function setTextContent(node, text) {
  node.textContent = text;
}

export default setTextContent;

11.7 DOMPropertyOperations.js #

src\react-dom-bindings\src\client\DOMPropertyOperations.js

export function setValueForProperty(node, name, value) {
  if (value === null) {
    node.removeAttribute(name);
  } else {
    node.setAttribute(name, value);
  }
}

12.commitRoot #

12.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
+import { MutationMask, NoFlags } from "./ReactFiberFlags";
let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
+ const finishedWork = root.current.alternate;
+ printFiber(finishedWork);
+ console.log(`~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`);
+ root.finishedWork = finishedWork;
+ commitRoot(root);
}
+function commitRoot(root) {
+  const { finishedWork } = root;
+  const subtreeHasEffects =
+    (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
+  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
+  if (subtreeHasEffects || rootHasEffect) {
+    console.log("commitRoot");
+  }
+  root.current = finishedWork;
+}
+function printFiber(fiber) {
+  /*
+  fiber.flags &= ~Forked;
+  fiber.flags &= ~PlacementDEV;
+  fiber.flags &= ~Snapshot;
+  fiber.flags &= ~PerformedWork;
+  */
+  if (fiber.flags !== 0) {
+    console.log(
+      getFlags(fiber.flags),
+      getTag(fiber.tag),
+      typeof fiber.type === "function" ? fiber.type.name : fiber.type,
+      fiber.memoizedProps
+    );
+    if (fiber.deletions) {
+      for (let i = 0; i < fiber.deletions.length; i++) {
+        const childToDelete = fiber.deletions[i];
+        console.log(getTag(childToDelete.tag), childToDelete.type, childToDelete.+memoizedProps);
+      }
+    }
+  }
+  let child = fiber.child;
+  while (child) {
+    printFiber(child);
+    child = child.sibling;
+  }
+}
+function getTag(tag) {
+  switch (tag) {
+    case FunctionComponent:
+      return `FunctionComponent`;
+    case HostRoot:
+      return `HostRoot`;
+    case HostComponent:
+      return `HostComponent`;
+    case HostText:
+      return HostText;
+    default:
+      return tag;
+  }
+}
+function getFlags(flags) {
+  if (flags === (Update | Placement | ChildDeletion)) {
+    return `自己移动和子元素有删除`;
+  }
+  if (flags === (ChildDeletion | Update)) {
+    return `自己有更新和子元素有删除`;
+  }
+  if (flags === ChildDeletion) {
+    return `子元素有删除`;
+  }
+  if (flags === (Placement | Update)) {
+    return `移动并更新`;
+  }
+  if (flags === Placement) {
+    return `插入`;
+  }
+  if (flags === Update) {
+    return `更新`;
+  }
+  return flags;
+}

function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

13.commitMutationEffectsOnFiber #

13.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags } from "./ReactFiberFlags";
+import { commitMutationEffectsOnFiber } from "./ReactFiberCommitWork";
let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
  root.finishedWork = finishedWork;
  commitRoot(root);
}
function commitRoot(root) {
  const { finishedWork } = root;
  const subtreeHasEffects =
    (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
+   commitMutationEffectsOnFiber(finishedWork, root);
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

13.2 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText } from "./ReactWorkTags";
import { MutationMask, Placement } from "./ReactFiberFlags";
function recursivelyTraverseMutationEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function commitPlacement(finishedWork) {
  console.log("commitPlacement", finishedWork);
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  switch (finishedWork.tag) {
    case HostRoot:
    case HostComponent:
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

14.commitPlacement #

14.1 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText } from "./ReactWorkTags";
import { MutationMask, Placement } from "./ReactFiberFlags";
+import {
+  insertBefore,
+  appendChild,
+} from "react-dom-bindings/src/client/ReactDOMHostConfig";
function recursivelyTraverseMutationEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
+function isHostParent(fiber) {
+  return fiber.tag === HostComponent || fiber.tag === HostRoot;
+}
+function getHostParentFiber(fiber) {
+  let parent = fiber.return;
+  while (parent !== null) {
+    if (isHostParent(parent)) {
+      return parent;
+    }
+    parent = parent.return;
+  }
+  return parent;
+}
+function insertOrAppendPlacementNode(node, before, parent) {
+  const { tag } = node;
+  const isHost = tag === HostComponent || tag === HostText;
+  if (isHost) {
+    const { stateNode } = node;
+    if (before) {
+      insertBefore(parent, stateNode, before);
+    } else {
+      appendChild(parent, stateNode);
+    }
+  } else {
+    const { child } = node;
+    if (child !== null) {
+      insertOrAppendPlacementNode(child, before, parent);
+      let { sibling } = child;
+      while (sibling !== null) {
+        insertOrAppendPlacementNode(sibling, before, parent);
+        sibling = sibling.sibling;
+      }
+    }
+  }
+}
+function getHostSibling(fiber) {
+  let node = fiber;
+  siblings: while (true) {
+    // 如果我们没有找到任何东西，让我们试试下一个弟弟
+    while (node.sibling === null) {
+      if (node.return === null || isHostParent(node.return)) {
+        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
+        return null;
+      }
+      node = node.return;
+    }
+    // node.sibling.return = node.return
+    node = node.sibling;
+    while (node.tag !== HostComponent && node.tag !== HostText) {
+      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
+      // 试着向下搜索，直到找到为止
+      if (node.flags & Placement) {
+        // 如果我们没有孩子，可以试试弟弟
+        continue siblings;
+      } else {
+        // node.child.return = node
+        node = node.child;
+      }
+    } // Check if this host node is stable or about to be placed.
+    // 检查此原生节点是否稳定可以放置
+    if (!(node.flags & Placement)) {
+      // 找到它了!
+      return node.stateNode;
+    }
+  }
+}
function commitPlacement(finishedWork) {
+  const parentFiber = getHostParentFiber(finishedWork);
+  switch (parentFiber.tag) {
+    case HostComponent: {
+      const parent = parentFiber.stateNode;
+      const before = getHostSibling(finishedWork);
+      insertOrAppendPlacementNode(finishedWork, before, parent);
+      break;
+    }
+    case HostRoot: {
+      const parent = parentFiber.stateNode.containerInfo;
+      const before = getHostSibling(finishedWork);
+      insertOrAppendPlacementNode(finishedWork, before, parent);
+      break;
+    }
+    default:
+      break;
+  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  switch (finishedWork.tag) {
    case HostRoot:
    case HostComponent:
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

14.2 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

import { setInitialProperties } from "./ReactDOMComponent";
export function shouldSetTextContent(type, props) {
  return (
    typeof props.children === "string" || typeof props.children === "number"
  );
}
export const appendInitialChild = (parent, child) => {
  parent.appendChild(child);
};
export const createInstance = (type, props, internalInstanceHandle) => {
  const domElement = document.createElement(type);
  return domElement;
};
export const createTextInstance = (content) => document.createTextNode(content);
export function finalizeInitialChildren(domElement, type, props) {
  setInitialProperties(domElement, type, props);
}
+export function appendChild(parentInstance, child) {
+  parentInstance.appendChild(child);
+}
+export function insertBefore(parentInstance, child, beforeChild) {
+  parentInstance.insertBefore(child, beforeChild);
+}

15.函数组件 #

15.1 src\main.jsx #

src\main.jsx

import { createRoot } from "react-dom/client";
+function FunctionComponent() {
+  return (
+    <h1>
+      hello<span style={{ color: "red" }}>world</span>
+    </h1>
+  );
+}
+let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

15.2 ReactWorkTags.js #

src\react-reconciler\src\ReactWorkTags.js

+export const FunctionComponent = 0;
+export const IndeterminateComponent = 2;
export const HostRoot = 3;
export const HostComponent = 5;
export const HostText = 6;

15.3 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import {
  HostRoot,
  HostComponent,
  HostText,
+ IndeterminateComponent,
+ FunctionComponent,
} from "./ReactWorkTags";
import { processUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import logger, { indent } from "shared/logger";
+import { renderWithHooks } from "react-reconciler/src/ReactFiberHooks";
function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(
      workInProgress,
      current.child,
      nextChildren
    );
  }
}
function updateHostRoot(current, workInProgress) {
  processUpdateQueue(workInProgress);
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
+function mountIndeterminateComponent(_current, workInProgress, Component) {
+  const props = workInProgress.pendingProps;
+  const value = renderWithHooks(null, workInProgress, Component, props);
+  workInProgress.tag = FunctionComponent;
+  reconcileChildren(null, workInProgress, value);
+  return workInProgress.child;
+}
export function beginWork(current, workInProgress) {
  logger(" ".repeat(indent.number) + "beginWork", workInProgress);
  indent.number += 2;
  switch (workInProgress.tag) {
+   case IndeterminateComponent: {
+     return mountIndeterminateComponent(
+       current,
+       workInProgress,
+       workInProgress.type
+     );
+   }
    case HostRoot:
      return updateHostRoot(current, workInProgress);
    case HostComponent:
      return updateHostComponent(current, workInProgress);
    case HostText:
    default:
      return null;
  }
}

15.4 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

export function renderWithHooks(current, workInProgress, Component, props) {
  const children = Component(props);
  return children;
}

15.5 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import {
  HostRoot,
  HostComponent,
  HostText,
+ FunctionComponent,
} from "./ReactWorkTags";
import { MutationMask, Placement } from "./ReactFiberFlags";
import {
  insertBefore,
  appendChild,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
function recursivelyTraverseMutationEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  switch (finishedWork.tag) {
    case HostRoot:
+   case FunctionComponent:
    case HostComponent:
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

16.注册事件名 #

DOMPluginEventSystem

16.1 src\main.jsx #

src\main.jsx

import { createRoot } from "react-dom/client";
function FunctionComponent() {
  return (
+   <h1
+     onClick={() => console.log("onClick FunctionComponent")}
+     onClickCapture={() => console.log("onClickCapture FunctionComponent")}
+   >
+     hello
+     <span
+       style={{ color: "red" }}
+       onClick={() => console.log("onClick span")}
+       onClickCapture={() => console.log("onClickCapture span")}
+     >
+       world
+     </span>
+   </h1>
  );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

16.2 ReactDOMRoot.js #

src\react-dom\src\client\ReactDOMRoot.js

import {
  createContainer,
  updateContainer,
} from "react-reconciler/src/ReactFiberReconciler";
+import { listenToAllSupportedEvents } from "react-dom-bindings/src/events/DOMPluginEventSystem";

function ReactDOMRoot(internalRoot) {
  this._internalRoot = internalRoot;
}
ReactDOMRoot.prototype.render = function render(children) {
  const root = this._internalRoot;
  root.containerInfo.innerHTML = "";
  updateContainer(children, root);
};
export function createRoot(container) {
  const root = createContainer(container);
+ listenToAllSupportedEvents(container);
  return new ReactDOMRoot(root);
}

16.3 DOMPluginEventSystem.js #

src\react-dom-bindings\src\events\DOMPluginEventSystem.js

import { allNativeEvents } from "./EventRegistry";
import * as SimpleEventPlugin from "./plugins/SimpleEventPlugin";
SimpleEventPlugin.registerEvents();
export function listenToAllSupportedEvents(rootContainerElement) {
  allNativeEvents.forEach((domEventName) => {
    console.log(domEventName);
  });
}

16.4 EventRegistry.js #

src\react-dom-bindings\src\events\EventRegistry.js

export const allNativeEvents = new Set();
export function registerTwoPhaseEvent(registrationName, dependencies) {
  registerDirectEvent(registrationName, dependencies);
  registerDirectEvent(registrationName + "Capture", dependencies);
}
export function registerDirectEvent(registrationName, dependencies) {
  for (let i = 0; i < dependencies.length; i++) {
    allNativeEvents.add(dependencies[i]); // click
  }
}

16.5 SimpleEventPlugin.js #

src\react-dom-bindings\src\events\plugins\SimpleEventPlugin.js

import { registerSimpleEvents } from "../DOMEventProperties";
export { registerSimpleEvents as registerEvents };

16.6 DOMEventProperties.js #

src\react-dom-bindings\src\events\DOMEventProperties.js

import { registerTwoPhaseEvent } from "./EventRegistry";

const simpleEventPluginEvents = ["click"];
function registerSimpleEvent(domEventName, reactName) {
  registerTwoPhaseEvent(reactName, [domEventName]);
}

export function registerSimpleEvents() {
  for (let i = 0; i < simpleEventPluginEvents.length; i++) {
    const eventName = simpleEventPluginEvents[i]; // click
    const domEventName = eventName.toLowerCase(); // click
    const capitalizedEvent = eventName[0].toUpperCase() + eventName.slice(1); // Click
    registerSimpleEvent(domEventName, `on${capitalizedEvent}`); // click=>onClick
  }
}

17.listenToNativeEvent #

17.1 DOMPluginEventSystem.js #

src\react-dom-bindings\src\events\DOMPluginEventSystem.js

import { allNativeEvents } from "./EventRegistry";
import * as SimpleEventPlugin from "./plugins/SimpleEventPlugin";
+import { createEventListenerWrapperWithPriority } from "./ReactDOMEventListener";
+import { IS_CAPTURE_PHASE } from "./EventSystemFlags";
+import { addEventCaptureListener, addEventBubbleListener } from "./EventListener";

SimpleEventPlugin.registerEvents();

export function listenToAllSupportedEvents(rootContainerElement) {
  allNativeEvents.forEach((domEventName) => {
+   listenToNativeEvent(domEventName, true, rootContainerElement);
+   listenToNativeEvent(domEventName, false, rootContainerElement);
  });
}

+export function listenToNativeEvent(domEventName, isCapturePhaseListener, +target) {
+  let eventSystemFlags = 0; // 冒泡 = 0 捕获 = 4
+  if (isCapturePhaseListener) {
+    eventSystemFlags |= IS_CAPTURE_PHASE;
+  }
+  addTrappedEventListener(target, domEventName, eventSystemFlags, isCapturePhaseListener);
+}
+function addTrappedEventListener(targetContainer, domEventName, +eventSystemFlags, isCapturePhaseListener) {
+  const listener = createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags);
+  if (isCapturePhaseListener) {
+    addEventCaptureListener(targetContainer, domEventName, listener);
+  } else {
+    addEventBubbleListener(targetContainer, domEventName, listener);
+  }
+}

17.2 EventSystemFlags.js #

src\react-dom-bindings\src\events\EventSystemFlags.js

export const IS_CAPTURE_PHASE = 1 << 2;

17.3 ReactDOMEventListener.js #

src\react-dom-bindings\src\events\ReactDOMEventListener.js

export function createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags) {
  const listenerWrapper = dispatchDiscreteEvent;
  return listenerWrapper.bind(null, domEventName, eventSystemFlags, targetContainer);
}
function dispatchDiscreteEvent(domEventName, eventSystemFlags, container, nativeEvent) {
  dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent);
}
export function dispatchEvent(domEventName, eventSystemFlags, targetContainer, nativeEvent) {
  console.log("dispatchEvent", domEventName, eventSystemFlags, targetContainer, nativeEvent);
}

17.4 EventListener.js #

src\react-dom-bindings\src\events\EventListener.js

export function addEventCaptureListener(target, eventType, listener) {
  target.addEventListener(eventType, listener, true);
  return listener;
}

export function addEventBubbleListener(target, eventType, listener) {
  target.addEventListener(eventType, listener, false);
  return listener;
}

18.extractEvents #

18.1 ReactDOMEventListener.js #

src\react-dom-bindings\src\events\ReactDOMEventListener.js

+import getEventTarget from "./getEventTarget";
+import { getClosestInstanceFromNode } from "../client/ReactDOMComponentTree";
+import { dispatchEventForPluginEventSystem } from "./DOMPluginEventSystem";

+export function createEventListenerWrapperWithPriority(
+  targetContainer,
+  domEventName,
+  eventSystemFlags
+) {
+  const listenerWrapper = dispatchDiscreteEvent;
+  return listenerWrapper.bind(null, domEventName, eventSystemFlags, targetContainer);
+}

+function dispatchDiscreteEvent(domEventName, eventSystemFlags, container, nativeEvent) {
+  dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent);
+}
export function dispatchEvent(domEventName, eventSystemFlags, targetContainer, nativeEvent) {
+ const nativeEventTarget = getEventTarget(nativeEvent);
+ const targetInst = getClosestInstanceFromNode(nativeEventTarget);
+ dispatchEventForPluginEventSystem(
+   domEventName,
+   eventSystemFlags,
+   nativeEvent,
+   targetInst,
+   targetContainer
+ );
}

18.2 getEventTarget.js #

src\react-dom-bindings\src\events\getEventTarget.js

function getEventTarget(nativeEvent) {
  const target = nativeEvent.target || nativeEvent.srcElement || window;
  return target;
}
export default getEventTarget;

18.3 ReactDOMComponentTree.js #

src\react-dom-bindings\src\client\ReactDOMComponentTree.js

const randomKey = Math.random().toString(36).slice(2);
const internalInstanceKey = "__reactFiber$" + randomKey;
const internalPropsKey = "__reactProps$" + randomKey;

export function getClosestInstanceFromNode(targetNode) {
  const targetInst = targetNode[internalInstanceKey];
  if (targetInst) {
    return targetInst;
  }
  return null;
}

export function getFiberCurrentPropsFromNode(node) {
  return node[internalPropsKey] || null;
}

export function precacheFiberNode(hostInst, node) {
  node[internalInstanceKey] = hostInst;
}

export function updateFiberProps(node, props) {
  node[internalPropsKey] = props;
}

18.4 DOMPluginEventSystem.js #

src\react-dom-bindings\src\events\DOMPluginEventSystem.js

import { allNativeEvents } from "./EventRegistry";
import * as SimpleEventPlugin from "./plugins/SimpleEventPlugin";
import { createEventListenerWrapperWithPriority } from "./ReactDOMEventListener";
import { IS_CAPTURE_PHASE } from "./EventSystemFlags";
import { addEventCaptureListener, addEventBubbleListener } from "./EventListener";
+import getEventTarget from "./getEventTarget";
+import getListener from "./getListener";
+import { HostComponent } from "react-reconciler/src/ReactWorkTags";

SimpleEventPlugin.registerEvents();

export function listenToAllSupportedEvents(rootContainerElement) {
  allNativeEvents.forEach((domEventName) => {
    listenToNativeEvent(domEventName, true, rootContainerElement);
    listenToNativeEvent(domEventName, false, rootContainerElement);
  });
}

export function listenToNativeEvent(domEventName, isCapturePhaseListener, target) {
  let eventSystemFlags = 0; // 冒泡 = 0 捕获 = 4
  if (isCapturePhaseListener) {
    eventSystemFlags |= IS_CAPTURE_PHASE;
  }
  addTrappedEventListener(target, domEventName, eventSystemFlags, isCapturePhaseListener);
}
function addTrappedEventListener(targetContainer, domEventName, eventSystemFlags, isCapturePhaseListener) {
  const listener = createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags);
  if (isCapturePhaseListener) {
    addEventCaptureListener(targetContainer, domEventName, listener);
  } else {
    addEventBubbleListener(targetContainer, domEventName, listener);
  }
}
+export function dispatchEventForPluginEventSystem(
+  domEventName,
+  eventSystemFlags,
+  nativeEvent,
+  targetInst,
+  targetContainer
+) {
+  dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer);
+}

+function dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer) {
+  const nativeEventTarget = getEventTarget(nativeEvent);
+  const dispatchQueue = [];
+  extractEvents(
+    dispatchQueue,
+    domEventName,
+    targetInst,
+    nativeEvent,
+    nativeEventTarget,
+    eventSystemFlags,
+    targetContainer
+  );
+  console.log("dispatchQueue", dispatchQueue);
+}

+function extractEvents(
+  dispatchQueue,
+  domEventName,
+  targetInst,
+  nativeEvent,
+  nativeEventTarget,
+  eventSystemFlags,
+  targetContainer
+) {
+  SimpleEventPlugin.extractEvents(
+    dispatchQueue,
+    domEventName,
+    targetInst,
+    nativeEvent,
+    nativeEventTarget,
+    eventSystemFlags,
+    targetContainer
+  );
+}

+export function accumulateSinglePhaseListeners(targetFiber, reactName, nativeEventType, inCapturePhase) {
+  const captureName = reactName + "Capture";
+  const reactEventName = inCapturePhase ? captureName : reactName;
+  const listeners = [];
+  let instance = targetFiber;
+  while (instance !== null) {
+    const { stateNode, tag } = instance;
+    if (tag === HostComponent && stateNode !== null) {
+      if (reactEventName !== null) {
+        const listener = getListener(instance, reactEventName);
+        if (listener !== null && listener !== undefined) {
+          listeners.push(createDispatchListener(instance, listener, stateNode));
+        }
+      }
+    }
+    instance = instance.return;
+  }
+  return listeners;
+}
+function createDispatchListener(instance, listener, currentTarget) {
+  return {
+    instance,
+    listener,
+    currentTarget,
+  };
+}

18.5 getListener.js #

src\react-dom-bindings\src\events\getListener.js

import { getFiberCurrentPropsFromNode } from "../client/ReactDOMComponentTree";

export default function getListener(inst, registrationName) {
  const stateNode = inst.stateNode;
  if (stateNode === null) {
    return null;
  }
  const props = getFiberCurrentPropsFromNode(stateNode);
  if (props === null) {
    return null;
  }
  const listener = props[registrationName];
  return listener;
}

18.6 SimpleEventPlugin.js #

src\react-dom-bindings\src\events\plugins\SimpleEventPlugin.js

import { registerSimpleEvents, topLevelEventsToReactNames } from "../DOMEventProperties";
import { SyntheticMouseEvent } from "../SyntheticEvent";
import { IS_CAPTURE_PHASE } from "../EventSystemFlags";
import { accumulateSinglePhaseListeners } from "../DOMPluginEventSystem";

+function extractEvents(dispatchQueue, domEventName, targetInst, nativeEvent, nativeEventTarget, eventSystemFlags) {
+  const reactName = topLevelEventsToReactNames.get(domEventName);
+  let SyntheticEventCtor;
+  switch (domEventName) {
+    case "click":
+      SyntheticEventCtor = SyntheticMouseEvent;
+      break;
+    default:
+      break;
+  }
+  const inCapturePhase = (eventSystemFlags & IS_CAPTURE_PHASE) !== 0;
+  const listeners = accumulateSinglePhaseListeners(targetInst, reactName, nativeEvent.type, inCapturePhase);
+  if (listeners.length > 0) {
+    const event = new SyntheticEventCtor(reactName, domEventName, targetInst, nativeEvent, nativeEventTarget);
+    dispatchQueue.push({
+      event,
+      listeners,
+    });
+  }
+}
+export { registerSimpleEvents as registerEvents, extractEvents };

18.7 SyntheticEvent.js #

src\react-dom-bindings\src\events\SyntheticEvent.js

import assign from "shared/assign";

function functionThatReturnsTrue() {
  return true;
}
function functionThatReturnsFalse() {
  return false;
}
const MouseEventInterface = {
  clientX: 0,
  clientY: 0,
};
function createSyntheticEvent(Interface) {
  function SyntheticBaseEvent(reactName, reactEventType, targetInst, nativeEvent, nativeEventTarget) {
    this._reactName = reactName;
    this.type = reactEventType;
    this._targetInst = targetInst;
    this.nativeEvent = nativeEvent;
    this.target = nativeEventTarget;
    for (const propName in Interface) {
      if (!Interface.hasOwnProperty(propName)) {
        continue;
      }
      this[propName] = nativeEvent[propName];
    }
    this.isDefaultPrevented = functionThatReturnsFalse;
    this.isPropagationStopped = functionThatReturnsFalse;
    return this;
  }

  assign(SyntheticBaseEvent.prototype, {
    preventDefault() {
      const event = this.nativeEvent;
      if (event.preventDefault) {
        event.preventDefault();
      } else {
        event.returnValue = false;
      }
      this.isDefaultPrevented = functionThatReturnsTrue;
    },
    stopPropagation() {
      const event = this.nativeEvent;
      if (event.stopPropagation) {
        event.stopPropagation();
      } else {
        event.cancelBubble = true;
      }
      this.isPropagationStopped = functionThatReturnsTrue;
    },
  });
  return SyntheticBaseEvent;
}
export const SyntheticMouseEvent = createSyntheticEvent(MouseEventInterface);

18.8 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

import { setInitialProperties } from "./ReactDOMComponent";
+import { precacheFiberNode, updateFiberProps } from "./ReactDOMComponentTree";

export function shouldSetTextContent(type, props) {
  return typeof props.children === "string" || typeof props.children === "number";
}
export const appendInitialChild = (parent, child) => {
  parent.appendChild(child);
};
export const createInstance = (type, props, internalInstanceHandle) => {
  const domElement = document.createElement(type);
+ precacheFiberNode(internalInstanceHandle, domElement);
+ updateFiberProps(domElement, props);
  return domElement;
};
export const createTextInstance = (content) => document.createTextNode(content);
export function finalizeInitialChildren(domElement, type, props) {
  setInitialProperties(domElement, type, props);
}
export function appendChild(parentInstance, child) {
  parentInstance.appendChild(child);
}
export function insertBefore(parentInstance, child, beforeChild) {
  parentInstance.insertBefore(child, beforeChild);
}

18.9 DOMEventProperties.js #

src\react-dom-bindings\src\events\DOMEventProperties.js

import { registerTwoPhaseEvent } from "./EventRegistry";
+export const topLevelEventsToReactNames = new Map();
const simpleEventPluginEvents = ["click"];
function registerSimpleEvent(domEventName, reactName) {
+ topLevelEventsToReactNames.set(domEventName, reactName);
  registerTwoPhaseEvent(reactName, [domEventName]);
}

export function registerSimpleEvents() {
  for (let i = 0; i < simpleEventPluginEvents.length; i++) {
    const eventName = simpleEventPluginEvents[i]; // click
    const domEventName = eventName.toLowerCase(); // click
    const capitalizedEvent = eventName[0].toUpperCase() + eventName.slice(1); // Click
    registerSimpleEvent(domEventName, `on${capitalizedEvent}`); // click=>onClick
  }
}

19.processDispatchQueue #

19.1 DOMPluginEventSystem.js #

src\react-dom-bindings\src\events\DOMPluginEventSystem.js

import { allNativeEvents } from "./EventRegistry";
import * as SimpleEventPlugin from "./plugins/SimpleEventPlugin";
import { createEventListenerWrapperWithPriority } from "./ReactDOMEventListener";
import { IS_CAPTURE_PHASE } from "./EventSystemFlags";
import { addEventCaptureListener, addEventBubbleListener } from "./EventListener";
import getEventTarget from "./getEventTarget";
import getListener from "./getListener";
import { HostComponent } from "react-reconciler/src/ReactWorkTags";

SimpleEventPlugin.registerEvents();

export function listenToAllSupportedEvents(rootContainerElement) {
  allNativeEvents.forEach((domEventName) => {
    listenToNativeEvent(domEventName, true, rootContainerElement);
    listenToNativeEvent(domEventName, false, rootContainerElement);
  });
}

export function listenToNativeEvent(domEventName, isCapturePhaseListener, target) {
  let eventSystemFlags = 0; // 冒泡 = 0 捕获 = 4
  if (isCapturePhaseListener) {
    eventSystemFlags |= IS_CAPTURE_PHASE;
  }
  addTrappedEventListener(target, domEventName, eventSystemFlags, isCapturePhaseListener);
}
function addTrappedEventListener(targetContainer, domEventName, eventSystemFlags, isCapturePhaseListener) {
  const listener = createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags);
  if (isCapturePhaseListener) {
    addEventCaptureListener(targetContainer, domEventName, listener);
  } else {
    addEventBubbleListener(targetContainer, domEventName, listener);
  }
}
export function dispatchEventForPluginEventSystem(
  domEventName,
  eventSystemFlags,
  nativeEvent,
  targetInst,
  targetContainer
) {
  dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer);
}

function dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer) {
  const nativeEventTarget = getEventTarget(nativeEvent);
  const dispatchQueue = [];
  extractEvents(
    dispatchQueue,
    domEventName,
    targetInst,
    nativeEvent,
    nativeEventTarget,
    eventSystemFlags,
    targetContainer
  );
+ processDispatchQueue(dispatchQueue, eventSystemFlags);
}

+export function processDispatchQueue(dispatchQueue, eventSystemFlags) {
+  const inCapturePhase = (eventSystemFlags & IS_CAPTURE_PHASE) !== 0;
+  for (let i = 0; i < dispatchQueue.length; i++) {
+    const { event, listeners } = dispatchQueue[i];
+    processDispatchQueueItemsInOrder(event, listeners, inCapturePhase); //  event system doesn't use pooling.
+  }
+}
+function processDispatchQueueItemsInOrder(event, dispatchListeners, inCapturePhase) {
+  if (inCapturePhase) {
+    for (let i = dispatchListeners.length - 1; i >= 0; i--) {
+      const { currentTarget, listener } = dispatchListeners[i];
+      if (event.isPropagationStopped()) {
+        return;
+      }
+      executeDispatch(event, listener, currentTarget);
+    }
+  } else {
+    for (let i = 0; i < dispatchListeners.length; i++) {
+      const { currentTarget, listener } = dispatchListeners[i];
+      if (event.isPropagationStopped()) {
+        return;
+      }
+      executeDispatch(event, listener, currentTarget);
+    }
+  }
+}
+function executeDispatch(event, listener, currentTarget) {
+  event.currentTarget = currentTarget;
+  listener(event);
+  event.currentTarget = null;
+}
function extractEvents(
  dispatchQueue,
  domEventName,
  targetInst,
  nativeEvent,
  nativeEventTarget,
  eventSystemFlags,
  targetContainer
) {
  SimpleEventPlugin.extractEvents(
    dispatchQueue,
    domEventName,
    targetInst,
    nativeEvent,
    nativeEventTarget,
    eventSystemFlags,
    targetContainer
  );
}

export function accumulateSinglePhaseListeners(targetFiber, reactName, nativeEventType, inCapturePhase) {
  const captureName = reactName + "Capture";
  const reactEventName = inCapturePhase ? captureName : reactName;
  const listeners = [];
  let instance = targetFiber;
  while (instance !== null) {
    const { stateNode, tag } = instance;
    if (tag === HostComponent && stateNode !== null) {
      if (reactEventName !== null) {
        const listener = getListener(instance, reactEventName);
        if (listener !== null && listener !== undefined) {
          listeners.push(createDispatchListener(instance, listener, stateNode));
        }
      }
    }
    instance = instance.return;
  }

  return listeners;
}
function createDispatchListener(instance, listener, currentTarget) {
  return {
    instance,
    listener,
    currentTarget,
  };
}

20.mountReducer #

20.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";
+const reducer = (state, action) => {
+  if (action.type === "add") return state + 1;
+  return state;
+};
function FunctionComponent() {
+  const [number, setNumber] = React.useReducer(reducer, 0);
+  return <button onClick={() => setNumber({ type: "add" })}>{number}</button>;
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

20.2 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

+import ReactSharedInternals from "shared/ReactSharedInternals";
+
+const { ReactCurrentDispatcher } = ReactSharedInternals;
+let currentlyRenderingFiber = null;
+let workInProgressHook = null;
+
+function mountWorkInProgressHook() {
+  const hook = {
+    memoizedState: null,
+    queue: null,
+    next: null,
+  };
+  if (workInProgressHook === null) {
+    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
+  } else {
+    workInProgressHook = workInProgressHook.next = hook;
+  }
+  return workInProgressHook;
+}
+function dispatchReducerAction(fiber, queue, action) {
+  console.log("dispatchReducerAction", action);
+}
+const HooksDispatcherOnMountInDEV = {
+  useReducer:mountReducer
+};
+function useReducer(reducer, initialArg){
+    const hook = mountWorkInProgressHook();
+    hook.memoizedState = initialArg;
+    const queue = {
+      pending: null,
+      dispatch: null,
+    };
+    hook.queue = queue;
+    const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
+    return [hook.memoizedState, dispatch];
}
export function renderWithHooks(current, workInProgress, Component, props) {
+ currentlyRenderingFiber = workInProgress;
+ if (current !== null && current.memoizedState !== null) {
+ } else {
+   ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
+ }
  const children = Component(props);
+ currentlyRenderingFiber = null;
  return children;
}

20.3 react\index.js #

src\react\index.js

export { __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED, useReducer } from "./src/React";

20.4 React.js #

src\react\src\React.js

import { useReducer } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";

export { useReducer, ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED };

20.5 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

20.6 ReactCurrentDispatcher.js #

src\react\src\ReactCurrentDispatcher.js

const ReactCurrentDispatcher = {
  current: null,
};
export default ReactCurrentDispatcher;

20.7 ReactSharedInternals.js #

src\react\src\ReactSharedInternals.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

const ReactSharedInternals = {
  ReactCurrentDispatcher,
};
export default ReactSharedInternals;

20.8 ReactSharedInternals.js #

src\shared\ReactSharedInternals.js

import * as React from "react";

const ReactSharedInternals = React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED;
export default ReactSharedInternals;

21.updateReducer #

21.1 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
+import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
+import { scheduleUpdateOnFiber } from "./ReactFiberWorkLoop";

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
+let currentHook = null;

function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
+ const update = {
+   action,
+   next: null,
+ };
+ const root = enqueueConcurrentHookUpdate(fiber, queue, update);
+ scheduleUpdateOnFiber(root, fiber);
}
const HooksDispatcherOnMountInDEV = {
  useReducer:mountReducer
};
function mountReducer(reducer, initialArg) {
    const hook = mountWorkInProgressHook();
    hook.memoizedState = initialArg;
    const queue = {
      pending: null,
      dispatch: null,
    };
    hook.queue = queue;
    const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
    return [hook.memoizedState, dispatch];
}
+function updateWorkInProgressHook() {
+  if (currentHook === null) {
+    const current = currentlyRenderingFiber.alternate
+    currentHook = current.memoizedState
+  } else {
+    currentHook = currentHook.next
+  }
+  const newHook = {
+    memoizedState: currentHook.memoizedState,
+    queue: currentHook.queue,
+    next: null
+  }
+  if (workInProgressHook === null) {
+    currentlyRenderingFiber.memoizedState = workInProgressHook = newHook
+  } else {
+    workInProgressHook = workInProgressHook.next = newHook
+  }
+  return workInProgressHook
+}
+const HooksDispatcherOnUpdateInDEV = {
+  useReducer：updateReducer
+};
+function updateReducer(reducer) {
+  const hook = updateWorkInProgressHook()
+  const queue = hook.queue
+  queue.lastRenderedReducer = reducer
+  const current = currentHook
+  const pendingQueue = queue.pending
+  let newState = current.memoizedState
+  if (pendingQueue !== null) {
+    queue.pending = null
+    const first = pendingQueue.next
+    let update = first
+    do {
+      if (update.hasEagerState) {
+        newState = update.eagerState
+      } else {
+        const action = update.action
+        newState = reducer(newState, action)
+      }
+      update = update.next
+    } while (update !== null && update !== first)
+  }
+  hook.memoizedState = queue.lastRenderedState = newState
+  return [hook.memoizedState, queue.dispatch]
+},
export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  if (current !== null && current.memoizedState !== null) {
+   ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
+ workInProgressHook = null;
+ currentHook = null;
  return children;
}

21.2 ReactFiberConcurrentUpdates.js #

src\react-reconciler\src\ReactFiberConcurrentUpdates.js

import { HostRoot } from "./ReactWorkTags";

+const concurrentQueues = [];
+let concurrentQueuesIndex = 0;

export function markUpdateLaneFromFiberToRoot(sourceFiber) {
  let node = sourceFiber;
  let parent = sourceFiber.return;
  while (parent !== null) {
    node = parent;
    parent = parent.return;
  }
  if (node.tag === HostRoot) {
    const root = node.stateNode;
    return root;
  }
  return null;
}
+export function enqueueConcurrentHookUpdate(fiber, queue, update) {
+  enqueueUpdate(fiber, queue, update);
+  return getRootForUpdatedFiber(fiber);
+}
+function enqueueUpdate(fiber, queue, update) {
+  concurrentQueues[concurrentQueuesIndex++] = fiber;
+  concurrentQueues[concurrentQueuesIndex++] = queue;
+  concurrentQueues[concurrentQueuesIndex++] = update;
+}
+function getRootForUpdatedFiber(sourceFiber) {
+  let node = sourceFiber;
+  let parent = node.return;
+  while (parent !== null) {
+    node = parent;
+    parent = node.return;
+  }
+  return node.tag === HostRoot ? node.stateNode : null;
+}

+export function finishQueueingConcurrentUpdates() {
+  const endIndex = concurrentQueuesIndex;
+  concurrentQueuesIndex = 0;
+  let i = 0;
+  while (i < endIndex) {
+    const fiber = concurrentQueues[i++];
+    const queue = concurrentQueues[i++];
+    const update = concurrentQueues[i++];
+    if (queue !== null && update !== null) {
+      const pending = queue.pending;
+      if (pending === null) {
+        update.next = update;
+      } else {
+        update.next = pending.next;
+        pending.next = update;
+      }
+      queue.pending = update;
+    }
+  }
+}

21.3 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags } from "./ReactFiberFlags";
import { commitMutationEffectsOnFiber } from "./ReactFiberCommitWork";
+import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";

let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
  root.finishedWork = finishedWork;
  commitRoot(root);
}
function commitRoot(root) {
  const { finishedWork } = root;
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffectsOnFiber(finishedWork, root);
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
+ finishQueueingConcurrentUpdates();
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

21.4 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import { HostRoot, HostComponent, HostText, IndeterminateComponent, FunctionComponent } from "./ReactWorkTags";
import { processUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import logger, { indent } from "shared/logger";
import { renderWithHooks } from "react-reconciler/src/ReactFiberHooks";
function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(workInProgress, current.child, nextChildren);
  }
}
function updateHostRoot(current, workInProgress) {
  processUpdateQueue(workInProgress);
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function mountIndeterminateComponent(_current, workInProgress, Component) {
  const props = workInProgress.pendingProps;
  const value = renderWithHooks(null, workInProgress, Component, props);
  workInProgress.tag = FunctionComponent;
  reconcileChildren(null, workInProgress, value);
  return workInProgress.child;
}
+function updateFunctionComponent(current, workInProgress, Component, nextProps) {
+  const nextChildren = renderWithHooks(current, workInProgress, Component, nextProps);
+  reconcileChildren(current, workInProgress, nextChildren);
+  return workInProgress.child;
+}
export function beginWork(current, workInProgress) {
  //logger(" ".repeat(indent.number) + "beginWork", workInProgress);
  indent.number += 2;
  switch (workInProgress.tag) {
    case IndeterminateComponent: {
      return mountIndeterminateComponent(current, workInProgress, workInProgress.type);
    }
+   case FunctionComponent: {
+     const Component = workInProgress.type;
+     const resolvedProps = workInProgress.pendingProps;
+     return updateFunctionComponent(current, workInProgress, Component, resolvedProps);
+   }
    case HostRoot:
      return updateHostRoot(current, workInProgress);
    case HostComponent:
      return updateHostComponent(current, workInProgress);
    case HostText:
    default:
      return null;
  }
}

21.5 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
import { Placement } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
+ function useFiber(fiber, pendingProps) {
+   const clone = createWorkInProgress(fiber, pendingProps);
+   clone.index = 0;
+   clone.sibling = null;
+   return clone;
+ }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
+   const key = element.key;
+   let child = currentFirstChild;
+   while (child !== null) {
+     if (child.key === key) {
+       const elementType = element.type;
+       if (child.type === elementType) {
+         const existing = useFiber(child, element.props);
+         existing.return = returnFiber;
+         return existing;
+       }
+     }
+     child = child.sibling;
+   }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
+   if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, newIndex) {
    newFiber.index = newIndex;
    if (shouldTrackSideEffects) newFiber.flags |= Placement;
  }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    for (; newIdx < newChildren.length; newIdx++) {
      const newFiber = createChild(returnFiber, newChildren[newIdx]);
      if (newFiber === null) {
        continue;
      }
      placeChild(newFiber, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
    }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

21.6 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
+ prepareUpdate,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HostComponent, HostRoot, HostText } from "./ReactWorkTags";
+import { NoFlags, Update } from "./ReactFiberFlags";
import logger, { indent } from "shared/logger";
function bubbleProperties(completedWork) {
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}
+function markUpdate(workInProgress) {
+  workInProgress.flags |= Update;
+}
+function updateHostComponent(current, workInProgress, type, newProps) {
+  const oldProps = current.memoizedProps;
+  const instance = workInProgress.stateNode;
+  const updatePayload = prepareUpdate(instance, type, oldProps, newProps);
+  workInProgress.updateQueue = updatePayload;
+  if (updatePayload) {
+    markUpdate(workInProgress);
+  }
+}
export function completeWork(current, workInProgress) {
  indent.number -= 2;
  //logger(" ".repeat(indent.number) + "completeWork", workInProgress);
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
+     if (current !== null && workInProgress.stateNode != null) {
+       updateHostComponent(current, workInProgress, type, newProps);
+       console.log("updatePayload", workInProgress.updateQueue);
+     } else {
        const instance = createInstance(type, newProps, workInProgress);
        appendAllChildren(instance, workInProgress);
        workInProgress.stateNode = instance;
        finalizeInitialChildren(instance, type, newProps);
+     }
+     bubbleProperties(workInProgress);
      break;
    }
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
    default:
      break;
  }
}

21.7 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
export const Placement = 0b00000000000000000000000010;
+export const Update = 0b00000000000000000000000100;
+export const MutationMask = Placement | Update;

21.8 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

+import { setInitialProperties, diffProperties } from "./ReactDOMComponent";
import { precacheFiberNode, updateFiberProps } from "./ReactDOMComponentTree";

export function shouldSetTextContent(type, props) {
  return typeof props.children === "string" || typeof props.children === "number";
}
export const appendInitialChild = (parent, child) => {
  parent.appendChild(child);
};
export const createInstance = (type, props, internalInstanceHandle) => {
  const domElement = document.createElement(type);
  precacheFiberNode(internalInstanceHandle, domElement);
  updateFiberProps(domElement, props);
  return domElement;
};
export const createTextInstance = (content) => document.createTextNode(content);
export function finalizeInitialChildren(domElement, type, props) {
  setInitialProperties(domElement, type, props);
}
export function appendChild(parentInstance, child) {
  parentInstance.appendChild(child);
}
export function insertBefore(parentInstance, child, beforeChild) {
  parentInstance.insertBefore(child, beforeChild);
}

+export function prepareUpdate(domElement, type, oldProps, newProps) {
+  return diffProperties(domElement, type, oldProps, newProps);
+}

21.9 ReactDOMComponent.js #

src\react-dom-bindings\src\client\ReactDOMComponent.js

import { setValueForStyles } from "./CSSPropertyOperations";
import setTextContent from "./setTextContent";
import { setValueForProperty } from "./DOMPropertyOperations";
const CHILDREN = "children";
const STYLE = "style";
function setInitialDOMProperties(tag, domElement, nextProps) {
  for (const propKey in nextProps) {
    if (nextProps.hasOwnProperty(propKey)) {
      const nextProp = nextProps[propKey];
      if (propKey === STYLE) {
        setValueForStyles(domElement, nextProp);
      } else if (propKey === CHILDREN) {
        if (typeof nextProp === "string") {
          setTextContent(domElement, nextProp);
        } else if (typeof nextProp === "number") {
          setTextContent(domElement, `${nextProp}`);
        }
      } else if (nextProp != null) {
        setValueForProperty(domElement, propKey, nextProp);
      }
    }
  }
}
export function setInitialProperties(domElement, tag, props) {
  setInitialDOMProperties(tag, domElement, props);
}

+export function diffProperties(domElement, tag, lastProps, nextProps) {
+  let updatePayload = null;
+  let propKey;
+  let styleName;
+  let styleUpdates = null;
+  for (propKey in lastProps) {
+    if (nextProps.hasOwnProperty(propKey) || !lastProps.hasOwnProperty(propKey) || lastProps[propKey] == null) {
+      continue;
+    }
+    if (propKey === STYLE) {
+      const lastStyle = lastProps[propKey];
+      for (styleName in lastStyle) {
+        if (lastStyle.hasOwnProperty(styleName)) {
+          if (!styleUpdates) {
+            styleUpdates = {};
+          }
+          styleUpdates[styleName] = "";
+        }
+      }
+    } else {
+      (updatePayload = updatePayload || []).push(propKey, null);
+    }
+  }
+  for (propKey in nextProps) {
+    const nextProp = nextProps[propKey];
+    const lastProp = lastProps != null ? lastProps[propKey] : undefined;
+    if (!nextProps.hasOwnProperty(propKey) || nextProp === lastProp || (nextProp == null && lastProp == null)) {
+      continue;
+    }
+    if (propKey === STYLE) {
+      if (lastProp) {
+        for (styleName in lastProp) {
+          if (lastProp.hasOwnProperty(styleName) && (!nextProp || !nextProp.hasOwnProperty(styleName))) {
+            if (!styleUpdates) {
+              styleUpdates = {};
+            }
+            styleUpdates[styleName] = "";
+          }
+        }
+        for (styleName in nextProp) {
+          if (nextProp.hasOwnProperty(styleName) && lastProp[styleName] !== nextProp[styleName]) {
+            if (!styleUpdates) {
+              styleUpdates = {};
+            }
+            styleUpdates[styleName] = nextProp[styleName];
+          }
+        }
+      } else {
+        if (!styleUpdates) {
+          if (!updatePayload) {
+            updatePayload = [];
+          }
+          updatePayload.push(propKey, styleUpdates);
+        }
+        styleUpdates = nextProp;
+      }
+    } else if (propKey === CHILDREN) {
+      if (typeof nextProp === "string" || typeof nextProp === "number") {
+        (updatePayload = updatePayload || []).push(propKey, "" + nextProp);
+      }
+    } else {
+      (updatePayload = updatePayload || []).push(propKey, nextProp);
+    }
+  }
+  if (styleUpdates) {
+    (updatePayload = updatePayload || []).push(STYLE, styleUpdates);
+  }
+  return updatePayload;
+}

22.commitUpdate #

22.1 DOMPluginEventSystem.js #

src\react-dom-bindings\src\events\DOMPluginEventSystem.js

import { allNativeEvents } from "./EventRegistry";
import * as SimpleEventPlugin from "./plugins/SimpleEventPlugin";
import { createEventListenerWrapperWithPriority } from "./ReactDOMEventListener";
import { IS_CAPTURE_PHASE } from "./EventSystemFlags";
import { addEventCaptureListener, addEventBubbleListener } from "./EventListener";
import getEventTarget from "./getEventTarget";
import getListener from "./getListener";
import { HostComponent } from "react-reconciler/src/ReactWorkTags";

SimpleEventPlugin.registerEvents();
+const listeningMarker = "_reactListening" + Math.random().toString(36).slice(2);
export function listenToAllSupportedEvents(rootContainerElement) {
+ if (!rootContainerElement[listeningMarker]) {
+   rootContainerElement[listeningMarker] = true;
    allNativeEvents.forEach((domEventName) => {
      listenToNativeEvent(domEventName, true, rootContainerElement);
      listenToNativeEvent(domEventName, false, rootContainerElement);
    });
+ }
}

export function listenToNativeEvent(domEventName, isCapturePhaseListener, target) {
  let eventSystemFlags = 0; // 冒泡 = 0 捕获 = 4
  if (isCapturePhaseListener) {
    eventSystemFlags |= IS_CAPTURE_PHASE;
  }
  addTrappedEventListener(target, domEventName, eventSystemFlags, isCapturePhaseListener);
}
function addTrappedEventListener(targetContainer, domEventName, eventSystemFlags, isCapturePhaseListener) {
  const listener = createEventListenerWrapperWithPriority(targetContainer, domEventName, eventSystemFlags);
  if (isCapturePhaseListener) {
    addEventCaptureListener(targetContainer, domEventName, listener);
  } else {
    addEventBubbleListener(targetContainer, domEventName, listener);
  }
}
export function dispatchEventForPluginEventSystem(
  domEventName,
  eventSystemFlags,
  nativeEvent,
  targetInst,
  targetContainer
) {
  dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer);
}

function dispatchEventsForPlugins(domEventName, eventSystemFlags, nativeEvent, targetInst, targetContainer) {
  const nativeEventTarget = getEventTarget(nativeEvent);
  const dispatchQueue = [];
  extractEvents(
    dispatchQueue,
    domEventName,
    targetInst,
    nativeEvent,
    nativeEventTarget,
    eventSystemFlags,
    targetContainer
  );
  processDispatchQueue(dispatchQueue, eventSystemFlags);
}

export function processDispatchQueue(dispatchQueue, eventSystemFlags) {
  const inCapturePhase = (eventSystemFlags & IS_CAPTURE_PHASE) !== 0;
  for (let i = 0; i < dispatchQueue.length; i++) {
    const { event, listeners } = dispatchQueue[i];
    processDispatchQueueItemsInOrder(event, listeners, inCapturePhase); //  event system doesn't use pooling.
  }
}
function processDispatchQueueItemsInOrder(event, dispatchListeners, inCapturePhase) {
  if (inCapturePhase) {
    for (let i = dispatchListeners.length - 1; i >= 0; i--) {
      const { currentTarget, listener } = dispatchListeners[i];
      if (event.isPropagationStopped()) {
        return;
      }
      executeDispatch(event, listener, currentTarget);
    }
  } else {
    for (let i = 0; i < dispatchListeners.length; i++) {
      const { currentTarget, listener } = dispatchListeners[i];
      if (event.isPropagationStopped()) {
        return;
      }
      executeDispatch(event, listener, currentTarget);
    }
  }
}
function executeDispatch(event, listener, currentTarget) {
  event.currentTarget = currentTarget;
  listener(event);
  event.currentTarget = null;
}
function extractEvents(
  dispatchQueue,
  domEventName,
  targetInst,
  nativeEvent,
  nativeEventTarget,
  eventSystemFlags,
  targetContainer
) {
  SimpleEventPlugin.extractEvents(
    dispatchQueue,
    domEventName,
    targetInst,
    nativeEvent,
    nativeEventTarget,
    eventSystemFlags,
    targetContainer
  );
}

export function accumulateSinglePhaseListeners(targetFiber, reactName, nativeEventType, inCapturePhase) {
  const captureName = reactName + "Capture";
  const reactEventName = inCapturePhase ? captureName : reactName;
  const listeners = [];
  let instance = targetFiber;
  while (instance !== null) {
    const { stateNode, tag } = instance;
    if (tag === HostComponent && stateNode !== null) {
      if (reactEventName !== null) {
        const listener = getListener(instance, reactEventName);
        if (listener !== null && listener !== undefined) {
          listeners.push(createDispatchListener(instance, listener, stateNode));
        }
      }
    }
    instance = instance.return;
  }

  return listeners;
}
function createDispatchListener(instance, listener, currentTarget) {
  return {
    instance,
    listener,
    currentTarget,
  };
}

22.2 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
  prepareUpdate,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
+import { HostComponent, HostRoot, HostText, FunctionComponent } from "./ReactWorkTags";
import { NoFlags, Update } from "./ReactFiberFlags";
import logger, { indent } from "shared/logger";
function bubbleProperties(completedWork) {
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}
function markUpdate(workInProgress) {
  workInProgress.flags |= Update;
}
function updateHostComponent(current, workInProgress, type, newProps) {
  const oldProps = current.memoizedProps;
  const instance = workInProgress.stateNode;
  const updatePayload = prepareUpdate(instance, type, oldProps, newProps);
  workInProgress.updateQueue = updatePayload;
  if (updatePayload) {
    markUpdate(workInProgress);
  }
}
export function completeWork(current, workInProgress) {
  indent.number -= 2;
  //logger(" ".repeat(indent.number) + "completeWork", workInProgress);
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
      if (current !== null && workInProgress.stateNode != null) {
        updateHostComponent(current, workInProgress, type, newProps);
      } else {
        const instance = createInstance(type, newProps, workInProgress);
        appendAllChildren(instance, workInProgress);
        workInProgress.stateNode = instance;
        finalizeInitialChildren(instance, type, newProps);
      }
      bubbleProperties(workInProgress);
      break;
    }
+   case FunctionComponent:
+     bubbleProperties(workInProgress);
+     break;
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
    default:
      break;
  }
}

22.3 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

+import { HostRoot, HostComponent, HostText, FunctionComponent } from "./ReactWorkTags";
+import { MutationMask, Placement, Update } from "./ReactFiberFlags";
+import { insertBefore, appendChild, commitUpdate } from "react-dom-bindings/src/client/ReactDOMHostConfig";
function recursivelyTraverseMutationEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
+ const current = finishedWork.alternate;
+ const flags = finishedWork.flags;
  switch (finishedWork.tag) {
+    case HostRoot: {
+      recursivelyTraverseMutationEffects(root, finishedWork);
+      commitReconciliationEffects(finishedWork);
+      break;
+    }
+    case FunctionComponent: {
+      recursivelyTraverseMutationEffects(root, finishedWork);
+      commitReconciliationEffects(finishedWork);
+      break;
+    }
+    case HostComponent: {
+      recursivelyTraverseMutationEffects(root, finishedWork);
+      commitReconciliationEffects(finishedWork);
+      if (flags & Update) {
+        const instance = finishedWork.stateNode;
+        if (instance != null) {
+          const newProps = finishedWork.memoizedProps;
+          const oldProps = current !== null ? current.memoizedProps : newProps;
+          const type = finishedWork.type;
+          const updatePayload = finishedWork.updateQueue;
+          finishedWork.updateQueue = null;
+          if (updatePayload !== null) {
+            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
+          }
+        }
+      }
+      break;
+    }
+    case HostText: {
+      recursivelyTraverseMutationEffects(root, finishedWork);
+      commitReconciliationEffects(finishedWork);
+      break;
+    }
    default: {
      break;
    }
  }
}

22.4 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

+import { setInitialProperties, diffProperties, updateProperties } from "./ReactDOMComponent";
import { precacheFiberNode, updateFiberProps } from "./ReactDOMComponentTree";

export function shouldSetTextContent(type, props) {
  return typeof props.children === "string" || typeof props.children === "number";
}
export const appendInitialChild = (parent, child) => {
  parent.appendChild(child);
};
export const createInstance = (type, props, internalInstanceHandle) => {
  const domElement = document.createElement(type);
  precacheFiberNode(internalInstanceHandle, domElement);
  updateFiberProps(domElement, props);
  return domElement;
};
export const createTextInstance = (content) => document.createTextNode(content);
export function finalizeInitialChildren(domElement, type, props) {
  setInitialProperties(domElement, type, props);
}
export function appendChild(parentInstance, child) {
  parentInstance.appendChild(child);
}
export function insertBefore(parentInstance, child, beforeChild) {
  parentInstance.insertBefore(child, beforeChild);
}

export function prepareUpdate(domElement, type, oldProps, newProps) {
  return diffProperties(domElement, type, oldProps, newProps);
}

+export function commitUpdate(domElement, updatePayload, type, oldProps, newProps) {
+  updateProperties(domElement, updatePayload, type, oldProps, newProps);
+  updateFiberProps(domElement, newProps);
+}

22.5 ReactDOMComponent.js #

src\react-dom-bindings\src\client\ReactDOMComponent.js

import { setValueForStyles } from "./CSSPropertyOperations";
import setTextContent from "./setTextContent";
import { setValueForProperty } from "./DOMPropertyOperations";
const CHILDREN = "children";
const STYLE = "style";
function setInitialDOMProperties(tag, domElement, nextProps) {
  for (const propKey in nextProps) {
    if (nextProps.hasOwnProperty(propKey)) {
      const nextProp = nextProps[propKey];
      if (propKey === STYLE) {
        setValueForStyles(domElement, nextProp);
      } else if (propKey === CHILDREN) {
        if (typeof nextProp === "string") {
          setTextContent(domElement, nextProp);
        } else if (typeof nextProp === "number") {
          setTextContent(domElement, `${nextProp}`);
        }
      } else if (nextProp != null) {
        setValueForProperty(domElement, propKey, nextProp);
      }
    }
  }
}
export function setInitialProperties(domElement, tag, props) {
  setInitialDOMProperties(tag, domElement, props);
}

export function diffProperties(domElement, tag, lastProps, nextProps) {
  let updatePayload = null;
  let propKey;
  let styleName;
  let styleUpdates = null;
  for (propKey in lastProps) {
    if (nextProps.hasOwnProperty(propKey) || !lastProps.hasOwnProperty(propKey) || lastProps[propKey] == null) {
      continue;
    }
    if (propKey === STYLE) {
      const lastStyle = lastProps[propKey];
      for (styleName in lastStyle) {
        if (lastStyle.hasOwnProperty(styleName)) {
          if (!styleUpdates) {
            styleUpdates = {};
          }
          styleUpdates[styleName] = "";
        }
      }
    } else {
      (updatePayload = updatePayload || []).push(propKey, null);
    }
  }
  for (propKey in nextProps) {
    const nextProp = nextProps[propKey];
    const lastProp = lastProps != null ? lastProps[propKey] : undefined;
    if (!nextProps.hasOwnProperty(propKey) || nextProp === lastProp || (nextProp == null && lastProp == null)) {
      continue;
    }
    if (propKey === STYLE) {
      if (lastProp) {
        for (styleName in lastProp) {
          if (lastProp.hasOwnProperty(styleName) && (!nextProp || !nextProp.hasOwnProperty(styleName))) {
            if (!styleUpdates) {
              styleUpdates = {};
            }
            styleUpdates[styleName] = "";
          }
        }
        for (styleName in nextProp) {
          if (nextProp.hasOwnProperty(styleName) && lastProp[styleName] !== nextProp[styleName]) {
            if (!styleUpdates) {
              styleUpdates = {};
            }
            styleUpdates[styleName] = nextProp[styleName];
          }
        }
      } else {
        if (!styleUpdates) {
          if (!updatePayload) {
            updatePayload = [];
          }
          updatePayload.push(propKey, styleUpdates);
        }
        styleUpdates = nextProp;
      }
    } else if (propKey === CHILDREN) {
      if (typeof nextProp === "string" || typeof nextProp === "number") {
        (updatePayload = updatePayload || []).push(propKey, "" + nextProp);
      }
    } else {
      (updatePayload = updatePayload || []).push(propKey, nextProp);
    }
  }
  if (styleUpdates) {
    (updatePayload = updatePayload || []).push(STYLE, styleUpdates);
  }
  return updatePayload;
}

+export function updateProperties(domElement, updatePayload) {
+  updateDOMProperties(domElement, updatePayload);
+}
+
+function updateDOMProperties(domElement, updatePayload) {
+  for (let i = 0; i < updatePayload.length; i += 2) {
+    const propKey = updatePayload[i];
+    const propValue = updatePayload[i + 1];
+    if (propKey === STYLE) {
+      setValueForStyles(domElement, propValue);
+    } else if (propKey === CHILDREN) {
+      setTextContent(domElement, propValue);
+    } else {
+      setValueForProperty(domElement, propKey, propValue);
+    }
+  }
+}

23.useState #

23.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  console.log("FunctionComponent render");
+ const [number, setNumber] = React.useState(0);
+ return <button onClick={() => setNumber(number + 1)}>{number}</button>;
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

23.2 react\index.js #

src\react\index.js

+export { __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED, useReducer, useState } from "./src/React";

23.3 React.js #

src\react\src\React.js

+import { useReducer, useState } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";

+export { useReducer, useState, ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED };

23.4 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

+export function useState(initialState) {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useState(initialState);
+}

23.5 objectIs.js #

src\shared\objectIs.js

const objectIs = Object.is;
export default objectIs;

23.6 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber } from "./ReactFiberWorkLoop";
+import is from "shared/objectIs";

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
+ useState: mountState,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
+ useState: updateState,
};
+function basicStateReducer(state, action) {
+  return typeof action === "function" ? action(state) : action;
+}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook()
  const queue = hook.queue
  queue.lastRenderedReducer = reducer
  const current = currentHook
  const pendingQueue = queue.pending
  let newState = current.memoizedState
  if (pendingQueue !== null) {
    queue.pending = null
    const first = pendingQueue.next
    let update = first
    do {
      if (update.hasEagerState) {
        newState = update.eagerState
      } else {
        const action = update.action
        newState = reducer(newState, action)
      }
      update = update.next
    } while (update !== null && update !== first)
  }
  hook.memoizedState = queue.lastRenderedState = newState
  return [hook.memoizedState, queue.dispatch]
}
+function mountState(initialState) {
+  const hook = mountWorkInProgressHook();
+  hook.memoizedState =  hook.baseState = initialState;
+  const queue = {
+    pending: null,
+    dispatch: null,
+    lastRenderedReducer: basicStateReducer,
+    lastRenderedState: initialState,
+  };
+  hook.queue = queue;
+  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
+  return [hook.memoizedState, dispatch];
+}
+function dispatchSetState(fiber, queue, action) {
+  const update = {
+    action,
+    hasEagerState: false,
+    eagerState: null,
+    next: null,
+  };
+  const lastRenderedReducer = queue.lastRenderedReducer;
+  const currentState = queue.lastRenderedState;
+  const eagerState = lastRenderedReducer(currentState, action);
+  update.hasEagerState = true;
+  update.eagerState = eagerState;
+  if (is(eagerState, currentState)) {
+    return;
+  }
+  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
+  scheduleUpdateOnFiber(root, fiber);
+}
+function updateState(initialState) {
+  return updateReducer(basicStateReducer, initialState);
+}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate
    currentHook = current.memoizedState
  } else {
    currentHook = currentHook.next
  }
  const newHook = {
    memoizedState: currentHook.memoizedState,
    queue: currentHook.queue,
    next: null
  }
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = newHook
  } else {
    workInProgressHook = workInProgressHook.next = newHook
  }
  return workInProgressHook
}

export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

24.单节点(key 相同,类型相同) #

24.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

+function FunctionComponent() {
+  const [number, setNumber] = React.useState(0);
+  return number === 0 ? (
+    <div onClick={() => setNumber(number + 1)} key="title" id="title">
+      title
+    </div>
+  ) : (
+    <div onClick={() => setNumber(number + 1)} key="title" id="title2">
+      title2
+    </div>
+  );
+}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

25.单节点 key 不同,类型相同 #

25.1 main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  const [number, setNumber] = React.useState(0);
+  return number === 0 ? (
+    <div onClick={() => setNumber(number + 1)} key="title1" id="title">
+      title
+    </div>
+  ) : (
+    <div onClick={() => setNumber(number + 1)} key="title2" id="title2">
+      title2
+    </div>
  );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

25.2 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
export const Placement = 0b00000000000000000000000010;
export const Update = 0b00000000000000000000000100;
+export const ChildDeletion = 0b00000000000000000000001000;
export const MutationMask = Placement | Update;

25.3 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
+ this.deletions = null;
  this.alternate = null;
}

25.4 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

+export function removeChild(parentInstance, child) {
+  parentInstance.removeChild(child);
+}

25.5 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
+import { Placement, ChildDeletion } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function useFiber(fiber, pendingProps) {
    const clone = createWorkInProgress(fiber, pendingProps);
    clone.index = 0;
    clone.sibling = null;
    return clone;
  }
+ function deleteChild(returnFiber, childToDelete) {
+   if (!shouldTrackSideEffects) {
+     return;
+   }
+   const deletions = returnFiber.deletions;
+   if (deletions === null) {
+     returnFiber.deletions = [childToDelete];
+     returnFiber.flags |= ChildDeletion;
+   } else {
+     deletions.push(childToDelete);
+   }
+ }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const key = element.key;
    let child = currentFirstChild;
    while (child !== null) {
      if (child.key === key) {
        const elementType = element.type;
        if (child.type === elementType) {
          const existing = useFiber(child, element.props);
          existing.return = returnFiber;
          return existing;
        }
+     } else {
+       deleteChild(returnFiber, child);
+     }
      child = child.sibling;
    }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, newIndex) {
    newFiber.index = newIndex;
    if (shouldTrackSideEffects) newFiber.flags |= Placement;
  }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    for (; newIdx < newChildren.length; newIdx++) {
      const newFiber = createChild(returnFiber, newChildren[newIdx]);
      if (newFiber === null) {
        continue;
      }
      placeChild(newFiber, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
    }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

25.6 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText, FunctionComponent } from "./ReactWorkTags";
import { MutationMask, Placement, Update } from "./ReactFiberFlags";
import {
  insertBefore,
  appendChild,
  commitUpdate,
+ removeChild,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
+let hostParent = null;
+function commitDeletionEffects(root, returnFiber, deletedFiber) {
+  let parent = returnFiber;
+  findParent: while (parent !== null) {
+    switch (parent.tag) {
+      case HostComponent: {
+        hostParent = parent.stateNode;
+        break findParent;
+      }
+      case HostRoot: {
+        hostParent = parent.stateNode.containerInfo;
+        break findParent;
+      }
+      default:
+        break;
+    }
+    parent = parent.return;
+  }
+  commitDeletionEffectsOnFiber(root, returnFiber, deletedFiber);
+  hostParent = null;
+}
+function commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, deletedFiber) {
+  switch (deletedFiber.tag) {
+    case HostComponent:
+    case HostText: {
+      recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, deletedFiber);
+      if (hostParent !== null) {
+          removeChild(hostParent, deletedFiber.stateNode);
+      }
+      break;
+    }
+    default:
+      break;
+  }
+}
+function recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, parent) {
+  let child = parent.child;
+  while (child !== null) {
+    commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, child);
+    child = child.sibling;
+  }
+}
function recursivelyTraverseMutationEffects(root, parentFiber) {
+ const deletions = parentFiber.deletions;
+ if (deletions !== null) {
+   for (let i = 0; i < deletions.length; i++) {
+     const childToDelete = deletions[i];
+     commitDeletionEffects(root, parentFiber, childToDelete);
+   }
+ }
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  const current = finishedWork.alternate;
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case HostRoot: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case FunctionComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case HostComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Update) {
        const instance = finishedWork.stateNode;
        if (instance != null) {
          const newProps = finishedWork.memoizedProps;
          const oldProps = current !== null ? current.memoizedProps : newProps;
          const type = finishedWork.type;
          const updatePayload = finishedWork.updateQueue;
          finishedWork.updateQueue = null;
          if (updatePayload !== null) {
            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
          }
        }
      }
      break;
    }
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

26.单节点 key 相同,类型不同 #

26.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  const [number, setNumber] = React.useState(0);
+  return number === 0 ? (
+    <div onClick={() => setNumber(number + 1)} key="title1" id="title1">
+      title1
+    </div>
+  ) : (
+    <p onClick={() => setNumber(number + 1)} key="title1" id="title1">
+      title1
+    </p>
+  );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

26.2 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
import { Placement, ChildDeletion } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function useFiber(fiber, pendingProps) {
    const clone = createWorkInProgress(fiber, pendingProps);
    clone.index = 0;
    clone.sibling = null;
    return clone;
  }
  function deleteChild(returnFiber, childToDelete) {
    if (!shouldTrackSideEffects) {
      return;
    }
    const deletions = returnFiber.deletions;
    if (deletions === null) {
      returnFiber.deletions = [childToDelete];
      returnFiber.flags |= ChildDeletion;
    } else {
      deletions.push(childToDelete);
    }
  }
+ function deleteRemainingChildren(returnFiber, currentFirstChild) {
+   if (!shouldTrackSideEffects) {
+     return null;
+   }
+   let childToDelete = currentFirstChild;
+   while (childToDelete !== null) {
+     deleteChild(returnFiber, childToDelete);
+     childToDelete = childToDelete.sibling;
+   }
+   return null;
+ }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const key = element.key;
    let child = currentFirstChild;
    while (child !== null) {
      if (child.key === key) {
        const elementType = element.type;
        if (child.type === elementType) {
+         deleteRemainingChildren(returnFiber, child.sibling);
          const existing = useFiber(child, element.props);
          existing.return = returnFiber;
          return existing;
        }
+       deleteRemainingChildren(returnFiber, child);
+       break;
      } else {
        deleteChild(returnFiber, child);
      }
      child = child.sibling;
    }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, newIndex) {
    newFiber.index = newIndex;
    if (shouldTrackSideEffects) newFiber.flags |= Placement;
  }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    for (; newIdx < newChildren.length; newIdx++) {
      const newFiber = createChild(returnFiber, newChildren[newIdx]);
      if (newFiber === null) {
        continue;
      }
      placeChild(newFiber, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
    }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

27.原来多个节点，现在只有一个节点 #

27.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  const [number, setNumber] = React.useState(0);
+ return number === 0 ? (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B">
+       B
+     </li>
+     <li key="C">C</li>
+   </ul>
+ ) : (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="B" id="B2">
+       B2
+     </li>
+   </ul>
+ );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

28.多节点 DIFF #

29.多个节点的数量和 key 相同，有的 type 不同 #

29.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  console.log("FunctionComponent");
  const [number, setNumber] = React.useState(0);
+ return number === 0 ? (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B">
+       B
+     </li>
+     <li key="C" id="C">
+       C
+     </li>
+   </ul>
+ ) : (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A2</li>
+     <p key="B" id="B2">
+       B2
+     </p>
+     <li key="C" id="C2">
+       C2
+     </li>
+   </ul>
+ );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

29.2 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
import { Placement, ChildDeletion } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function useFiber(fiber, pendingProps) {
    const clone = createWorkInProgress(fiber, pendingProps);
    clone.index = 0;
    clone.sibling = null;
    return clone;
  }
  function deleteChild(returnFiber, childToDelete) {
    if (!shouldTrackSideEffects) {
      return;
    }
    const deletions = returnFiber.deletions;
    if (deletions === null) {
      returnFiber.deletions = [childToDelete];
      returnFiber.flags |= ChildDeletion;
    } else {
      deletions.push(childToDelete);
    }
  }
  function deleteRemainingChildren(returnFiber, currentFirstChild) {
    if (!shouldTrackSideEffects) {
      return null;
    }
    let childToDelete = currentFirstChild;
    while (childToDelete !== null) {
      deleteChild(returnFiber, childToDelete);
      childToDelete = childToDelete.sibling;
    }
    return null;
  }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const key = element.key;
    let child = currentFirstChild;
    while (child !== null) {
      if (child.key === key) {
        const elementType = element.type;
        if (child.type === elementType) {
          deleteRemainingChildren(returnFiber, child.sibling);
          const existing = useFiber(child, element.props);
          existing.return = returnFiber;
          return existing;
        }
        deleteRemainingChildren(returnFiber, child);
        break;
      } else {
        deleteChild(returnFiber, child);
      }
      child = child.sibling;
    }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, newIndex) {
+   newFiber.index = newIndex;
+   if (!shouldTrackSideEffects) {
+     return;
+   }
+   const current = newFiber.alternate;
+   if (current !== null) {
+     return;
+   } else {
+     newFiber.flags |= Placement;
+   }
  }
+ function updateElement(returnFiber, current, element) {
+   const elementType = element.type;
+   if (current !== null) {
+     if (current.type === elementType) {
+       const existing = useFiber(current, element.props);
+       existing.return = returnFiber;
+       return existing;
+     }
+   }
+   const created = createFiberFromElement(element);
+   created.return = returnFiber;
+   return created;
+ }
+ function updateSlot(returnFiber, oldFiber, newChild) {
+   const key = oldFiber !== null ? oldFiber.key : null;
+   if (typeof newChild === "object" && newChild !== null) {
+     switch (newChild.$$typeof) {
+       case REACT_ELEMENT_TYPE: {
+         if (newChild.key === key) {
+           return updateElement(returnFiber, oldFiber, newChild);
+         }
+       }
+       default:
+         return null;
+     }
+     return null
+   }
+ }

  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
+   let oldFiber = currentFirstChild;
+   let nextOldFiber = null;
+   for (; oldFiber !== null && newIdx < newChildren.length; newIdx++) {
+     nextOldFiber = oldFiber.sibling;
+     const newFiber = updateSlot(returnFiber, oldFiber, newChildren[newIdx]);
+     if (newFiber === null) {
+       break;
+     }
+     if (shouldTrackSideEffects) {
+       if (oldFiber && newFiber.alternate === null) {
+         deleteChild(returnFiber, oldFiber);
+       }
+     }
+     placeChild(newFiber, newIdx);
+     if (previousNewFiber === null) {
+       resultingFirstChild = newFiber;
+     } else {
+       previousNewFiber.sibling = newFiber;
+     }
+     previousNewFiber = newFiber;
+     oldFiber = nextOldFiber;
+   }
+   if (newIdx === newChildren.length) {
+     deleteRemainingChildren(returnFiber, oldFiber);
+     return resultingFirstChild;
+   }
+   if (oldFiber === null) {
+     for (; newIdx < newChildren.length; newIdx++) {
+       const newFiber = createChild(returnFiber, newChildren[newIdx]);
+       if (newFiber === null) {
+         continue;
+       }
+       placeChild(newFiber, newIdx);
+       if (previousNewFiber === null) {
+         resultingFirstChild = newFiber;
+       } else {
+         previousNewFiber.sibling = newFiber;
+       }
+       previousNewFiber = newFiber;
+     }
+   }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

30.多个节点的类型和 key 全部相同，有新增元素 #

30.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  console.log("FunctionComponent");
  const [number, setNumber] = React.useState(0);
+ return number === 0 ? (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B">
+       B
+     </li>
+     <li key="C">C</li>
+   </ul>
+ ) : (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B2">
+       B2
+     </li>
+     <li key="C">C2</li>
+     <li key="D">D</li>
+   </ul>
+ );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

31.多个节点的类型和 key 全部相同，有删除老元素 #

31.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  console.log("FunctionComponent");
  const [number, setNumber] = React.useState(0);
+ return number === 0 ? (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B">
+       B
+     </li>
+     <li key="C">C</li>
+   </ul>
+ ) : (
+   <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="B2">
+       B2
+     </li>
+   </ul>
+ );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

32.多个节点数量不同、key 不同 #

32.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
  console.log("FunctionComponent");
  const [number, setNumber] = React.useState(0);
  return number === 0 ? (
    <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A</li>
+     <li key="B" id="b">
+       B
+     </li>
+     <li key="C">C</li>
+     <li key="D">D</li>
+     <li key="E">E</li>
+     <li key="F">F</li>
    </ul>
  ) : (
    <ul key="container" onClick={() => setNumber(number + 1)}>
+     <li key="A">A2</li>
+     <li key="C">C2</li>
+     <li key="E">E2</li>
+     <li key="B" id="b2">
+       B2
+     </li>
+     <li key="G">G</li>
+     <li key="D">D2</li>
    </ul>
  );
}
let element = <FunctionComponent />;
const root = createRoot(document.getElementById("root"));
root.render(element);

32.2 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.deletions = null;
  this.alternate = null;

+ this.index = 0;
}

32.3 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Placement, Update,ChildDeletion } from "./ReactFiberFlags";
import { commitMutationEffectsOnFiber } from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import { FunctionComponent, IndeterminateComponent, HostRoot, HostComponent, HostText } from "./ReactWorkTags";

let workInProgress = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
+ printFiber(finishedWork);
+ console.log(`~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`);
  root.finishedWork = finishedWork;
  commitRoot(root);
}
function commitRoot(root) {
  const { finishedWork } = root;
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffectsOnFiber(finishedWork, root);
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

+function printFiber(fiber) {
+  /*
+  fiber.flags &= ~Forked;
+  fiber.flags &= ~PlacementDEV;
+  fiber.flags &= ~Snapshot;
+  fiber.flags &= ~PerformedWork;
+  */
+  if (fiber.flags !== 0) {
+    console.log(
+      getFlags(fiber.flags),
+      getTag(fiber.tag),
+      typeof fiber.type === "function" ? fiber.type.name : fiber.type,
+      fiber.memoizedProps
+    );
+    if (fiber.deletions) {
+      for (let i = 0; i < fiber.deletions.length; i++) {
+        const childToDelete = fiber.deletions[i];
+        console.log(getTag(childToDelete.tag), childToDelete.type, childToDelete.+memoizedProps);
+      }
+    }
+  }
+  let child = fiber.child;
+  while (child) {
+    printFiber(child);
+    child = child.sibling;
+  }
+}
+function getTag(tag) {
+  switch (tag) {
+    case FunctionComponent:
+      return `FunctionComponent`;
+    case HostRoot:
+      return `HostRoot`;
+    case HostComponent:
+      return `HostComponent`;
+    case HostText:
+      return HostText;
+    default:
+      return tag;
+  }
+}
+function getFlags(flags) {
+  if (flags === (Update | Placement | ChildDeletion)) {
+    return `自己移动和子元素有删除`;
+  }
+  if (flags === (ChildDeletion | Update)) {
+    return `自己有更新和子元素有删除`;
+  }
+  if (flags === ChildDeletion) {
+    return `子元素有删除`;
+  }
+  if (flags === (Placement | Update)) {
+    return `移动并更新`;
+  }
+  if (flags === Placement) {
+    return `插入`;
+  }
+  if (flags === Update) {
+    return `更新`;
+  }
+  return flags;
+}

32.4 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
import { Placement, ChildDeletion } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function useFiber(fiber, pendingProps) {
    const clone = createWorkInProgress(fiber, pendingProps);
    clone.index = 0;
    clone.sibling = null;
    return clone;
  }
  function deleteChild(returnFiber, childToDelete) {
    if (!shouldTrackSideEffects) {
      return;
    }
    const deletions = returnFiber.deletions;
    if (deletions === null) {
      returnFiber.deletions = [childToDelete];
      returnFiber.flags |= ChildDeletion;
    } else {
      deletions.push(childToDelete);
    }
  }
  function deleteRemainingChildren(returnFiber, currentFirstChild) {
    if (!shouldTrackSideEffects) {
      return null;
    }
    let childToDelete = currentFirstChild;
    while (childToDelete !== null) {
      deleteChild(returnFiber, childToDelete);
      childToDelete = childToDelete.sibling;
    }
    return null;
  }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const key = element.key;
    let child = currentFirstChild;
    while (child !== null) {
      if (child.key === key) {
        const elementType = element.type;
        if (child.type === elementType) {
          deleteRemainingChildren(returnFiber, child.sibling);
          const existing = useFiber(child, element.props);
          existing.return = returnFiber;
          return existing;
        }
        deleteRemainingChildren(returnFiber, child);
        break;
      } else {
        deleteChild(returnFiber, child);
      }
      child = child.sibling;
    }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
+ function placeChild(newFiber, lastPlacedIndex, newIndex) {
+   newFiber.index = newIndex;
+   if (!shouldTrackSideEffects) {
+     return lastPlacedIndex;
+   }
+   const current = newFiber.alternate;
+   if (current !== null) {
+     const oldIndex = current.index;
+     if (oldIndex < lastPlacedIndex) {
+       newFiber.flags |= Placement;
+       return lastPlacedIndex;
+     } else {
+       return oldIndex;
+     }
+   } else {
+     newFiber.flags |= Placement;
+     return lastPlacedIndex;
+   }
+ }
  function updateElement(returnFiber, current, element) {
    const elementType = element.type;
    if (current !== null) {
      if (current.type === elementType) {
        const existing = useFiber(current, element.props);
        existing.return = returnFiber;
        return existing;
      }
    }
    const created = createFiberFromElement(element);
    created.return = returnFiber;
    return created;
  }
  function updateSlot(returnFiber, oldFiber, newChild) {
    const key = oldFiber !== null ? oldFiber.key : null;
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          if (newChild.key === key) {
            return updateElement(returnFiber, oldFiber, newChild);
          } else {
            return null;
          }
        }
        default:
          return null;
      }
    }
  }
+ function mapRemainingChildren(returnFiber, currentFirstChild) {
+   const existingChildren = new Map();
+   let existingChild = currentFirstChild;
+   while (existingChild !== null) {
+     if (existingChild.key !== null) {
+       existingChildren.set(existingChild.key, existingChild);
+     } else {
+       existingChildren.set(existingChild.index, existingChild);
+     }
+     existingChild = existingChild.sibling;
+   }
+   return existingChildren;
+ }
+ function updateTextNode(returnFiber, current, textContent) {
+   if (current === null || current.tag !== HostText) {
+     const created = createFiberFromText(textContent);
+     created.return = returnFiber;
+     return created;
+   } else {
+     const existing = useFiber(current, textContent);
+     existing.return = returnFiber;
+     return existing;
+   }
+ }
+ function updateFromMap(existingChildren, returnFiber, newIdx, newChild) {
+   if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
+     const matchedFiber = existingChildren.get(newIdx) || null;
+     return updateTextNode(returnFiber, matchedFiber, "" + newChild);
+   }
+   if (typeof newChild === "object" && newChild !== null) {
+     switch (newChild.$$typeof) {
+       case REACT_ELEMENT_TYPE: {
+         const matchedFiber = existingChildren.get(newChild.key === null ? newIdx : newChild.key) || null;
+         return updateElement(returnFiber, matchedFiber, newChild);
+       }
+     }
+   }
+   return null;
+ }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    let oldFiber = currentFirstChild;
    let nextOldFiber = null;
+   let lastPlacedIndex = 0;
    for (; oldFiber !== null && newIdx < newChildren.length; newIdx++) {
      nextOldFiber = oldFiber.sibling;
      const newFiber = updateSlot(returnFiber, oldFiber, newChildren[newIdx]);
      if (newFiber === null) {
        break;
      }
      if (shouldTrackSideEffects) {
        if (oldFiber && newFiber.alternate === null) {
          deleteChild(returnFiber, oldFiber);
        }
      }
+     lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
      oldFiber = nextOldFiber;
    }
    if (newIdx === newChildren.length) {
      deleteRemainingChildren(returnFiber, oldFiber);
      return resultingFirstChild;
    }
    if (oldFiber === null) {
      for (; newIdx < newChildren.length; newIdx++) {
        const newFiber = createChild(returnFiber, newChildren[newIdx]);
        if (newFiber === null) {
          continue;
        }
+       lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
        if (previousNewFiber === null) {
          resultingFirstChild = newFiber;
        } else {
          previousNewFiber.sibling = newFiber;
        }
        previousNewFiber = newFiber;
      }
    }
+   const existingChildren = mapRemainingChildren(returnFiber, oldFiber);
+   for (; newIdx < newChildren.length; newIdx++) {
+     const newFiber = updateFromMap(existingChildren, returnFiber, newIdx, newChildren[newIdx]);
+     if (newFiber !== null) {
+       if (shouldTrackSideEffects) {
+         if (newFiber.alternate !== null) {
+           existingChildren.delete(newFiber.key === null ? newIdx : newFiber.key);
+         }
+       }
+       lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
+       if (previousNewFiber === null) {
+         resultingFirstChild = newFiber;
+       } else {
+         previousNewFiber.sibling = newFiber;
+       }
+       previousNewFiber = newFiber;
+     }
+   }
+   if (shouldTrackSideEffects) {
+     existingChildren.forEach((child) => deleteChild(returnFiber, child));
+   }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

33.useEffect #

33.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function Counter() {
+ const [number, setNumber] = React.useState(0);
+ React.useEffect(() => {
+   console.log("useEffect1");
+   return () => {
+     console.log("destroy useEffect1");
+   };
+ });
+ React.useEffect(() => {
+   console.log("useEffect2");
+   return () => {
+     console.log("destroy useEffect2");
+   };
+ });
+ React.useEffect(() => {
+   console.log("useEffect3");
+   return () => {
+     console.log("destroy useEffect3");
+   };
+ });
+ return (
+   <div
+     onClick={() => {
+       setNumber(number + 1);
+     }}
+   >
+     {number}
+   </div>
+ );
}
let element = <Counter />;
const root = createRoot(document.getElementById("root"));
root.render(element);

33.2 react\index.js #

src\react\index.js

+export { __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED, useReducer, useState, useEffect } from "./src/React";

33.3 React.js #

src\react\src\React.js

+import { useReducer, useState, useEffect } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";

+export { useReducer, useState, useEffect, ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED };

33.4 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

export function useState(initialState) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

+export function useEffect(create,deps) {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useEffect(create,deps);
+}

33.5 ReactHookEffectTags.js #

src\react-reconciler\src\ReactHookEffectTags.js

export const HasEffect = 0b0001;
export const Passive = 0b1000;

33.6 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
export const Placement = 0b00000000000000000000000010;
export const Update = 0b00000000000000000000000100;
export const ChildDeletion = 0b00000000000000000000001000;
export const MutationMask = Placement | Update;
+export const Passive = 0b00000000000000010000000000;

33.7 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
+import { Passive as PassiveEffect } from "./ReactFiberFlags";
+import { HasEffect as HookHasEffect, Passive as HookPassive } from "./ReactHookEffectTags";

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
+ useEffect: mountEffect,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
+ useEffect: updateEffect,
};
+function updateEffect(create, deps) {
+  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
+}
+function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
+  const hook = updateWorkInProgressHook();
+  const nextDeps = deps === undefined ? null : deps;
+  let destroy;
+  if (currentHook !== null) {
+    const prevEffect = currentHook.memoizedState;
+    destroy = prevEffect.destroy;
+    if (nextDeps !== null) {
+      const prevDeps = prevEffect.deps;
+      if (areHookInputsEqual(nextDeps, prevDeps)) {
+        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
+        return;
+      }
+    }
+  }
+  currentlyRenderingFiber.flags |= fiberFlags;
+  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
+}
+function areHookInputsEqual(nextDeps, prevDeps) {
+  if (prevDeps === null) {
+    return false;
+  }
+  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
+    if (is(nextDeps[i], prevDeps[i])) {
+      continue;
+    }
+    return false;
+  }
+
+  return true;
+}
+function mountEffect(create, deps) {
+  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
+}
+function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
+  const hook = mountWorkInProgressHook();
+  const nextDeps = deps === undefined ? null : deps;
+  currentlyRenderingFiber.flags |= fiberFlags;
+  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
+}
+function pushEffect(tag, create, destroy, deps) {
+  const effect = {
+    tag,
+    create,
+    destroy,
+    deps,
+    next: null,
+  };
+  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
+  if (componentUpdateQueue === null) {
+    componentUpdateQueue = createFunctionComponentUpdateQueue();
+    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
+    componentUpdateQueue.lastEffect = effect.next = effect;
+  } else {
+    const lastEffect = componentUpdateQueue.lastEffect;
+    if (lastEffect === null) {
+      componentUpdateQueue.lastEffect = effect.next = effect;
+    } else {
+      const firstEffect = lastEffect.next;
+      lastEffect.next = effect;
+      effect.next = firstEffect;
+      componentUpdateQueue.lastEffect = effect;
+    }
+  }
+  return effect;
+}
+function createFunctionComponentUpdateQueue() {
+  return {
+    lastEffect: null,
+  };
+}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  const pendingQueue = queue.pending;
  let baseQueue = null;
  let newState = current.memoizedState;
  if (pendingQueue !== null) {
    baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    const first = baseQueue.next;
    let update = first;
    do {
      if (update.hasEagerState) {
        newState = update.eagerState;
      } else {
        const action = update.action;
        newState = reducer(newState, action);
      }
      update = update.next;
    } while (update !== null && update !== first);
  }
  hook.memoizedState = newState;
  queue.lastRenderedState = newState;
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const update = {
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const lastRenderedReducer = queue.lastRenderedReducer;
  const currentState = queue.lastRenderedState;
  const eagerState = lastRenderedReducer(currentState, action);
  update.hasEagerState = true;
  update.eagerState = eagerState;
  if (is(eagerState, currentState)) {
    return;
  }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
+ workInProgress.updateQueue = null;
+ workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

33.8 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
+import { MutationMask, NoFlags, Placement, Update, ChildDeletion, Passive } from "./ReactFiberFlags";
+import { commitMutationEffects, commitPassiveUnmountEffects, commitPassiveMountEffects } from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import { FunctionComponent, IndeterminateComponent, HostRoot, HostComponent, HostText } from "./ReactWorkTags";

let workInProgress = null;
+let rootDoesHavePassiveEffects = false;
+let rootWithPendingPassiveEffects = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
  printFiber(finishedWork);
  console.log(`~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`);
  root.finishedWork = finishedWork;
  commitRoot(root);
}
+export function flushPassiveEffects() {
+  if (rootWithPendingPassiveEffects !== null) {
+    const root = rootWithPendingPassiveEffects;
+    commitPassiveUnmountEffects(root.current);
+    commitPassiveMountEffects(root, root.current);
+  }
+}
function commitRoot(root) {
  const { finishedWork } = root;
+  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
+   if (!rootDoesHavePassiveEffects) {
+     rootDoesHavePassiveEffects = true;
+     scheduleCallback(flushPassiveEffects);
+   }
+ }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
+   commitMutationEffects(finishedWork, root);
+   root.current = finishedWork;
+   if (rootDoesHavePassiveEffects) {
+     rootDoesHavePassiveEffects = false;
+     rootWithPendingPassiveEffects = root;
+   }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

function printFiber(fiber) {
  /*
  fiber.flags &= ~Forked;
  fiber.flags &= ~PlacementDEV;
  fiber.flags &= ~Snapshot;
  fiber.flags &= ~PerformedWork;
  */
  if (fiber.flags !== 0) {
    console.log(
      getFlags(fiber.flags),
      getTag(fiber.tag),
      typeof fiber.type === "function" ? fiber.type.name : fiber.type,
      fiber.memoizedProps
    );
    if (fiber.deletions) {
      for (let i = 0; i < fiber.deletions.length; i++) {
        const childToDelete = fiber.deletions[i];
        console.log(getTag(childToDelete.tag), childToDelete.type, childToDelete.memoizedProps);
      }
    }
  }
  let child = fiber.child;
  while (child) {
    printFiber(child);
    child = child.sibling;
  }
}
function getTag(tag) {
  switch (tag) {
    case FunctionComponent:
      return `FunctionComponent`;
    case HostRoot:
      return `HostRoot`;
    case HostComponent:
      return `HostComponent`;
    case HostText:
      return HostText;
    default:
      return tag;
  }
}
function getFlags(flags) {
  if (flags === (Update | Placement | ChildDeletion)) {
    return `自己移动和子元素有删除`;
  }
  if (flags === (ChildDeletion | Update)) {
    return `自己有更新和子元素有删除`;
  }
  if (flags === ChildDeletion) {
    return `子元素有删除`;
  }
  if (flags === (Placement | Update)) {
    return `移动并更新`;
  }
  if (flags === Placement) {
    return `插入`;
  }
  if (flags === Update) {
    return `更新`;
  }
  return flags;
}

33.9 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText, FunctionComponent } from "./ReactWorkTags";
+import { MutationMask, Placement, Update, Passive } from "./ReactFiberFlags";
import { insertBefore, appendChild, commitUpdate, removeChild } from "react-dom-bindings/src/client/ReactDOMHostConfig";
+import { HasEffect as HookHasEffect, Passive as HookPassive } from "./ReactHookEffectTags";

+export function commitMutationEffects(finishedWork, root) {
+  commitMutationEffectsOnFiber(finishedWork, root);
+}
+export function commitPassiveUnmountEffects(finishedWork) {
+  commitPassiveUnmountOnFiber(finishedWork);
+}
+function commitPassiveUnmountOnFiber(finishedWork) {
+  switch (finishedWork.tag) {
+    case FunctionComponent: {
+      recursivelyTraversePassiveUnmountEffects(finishedWork);
+      if (finishedWork.flags & Passive) {
+        commitHookPassiveUnmountEffects(finishedWork, finishedWork.return, HookPassive | HookHasEffect);
+      }
+      break;
+    }
+    default: {
+      recursivelyTraversePassiveUnmountEffects(finishedWork);
+      break;
+    }
+  }
+}
+function recursivelyTraversePassiveUnmountEffects(parentFiber) {
+  if (parentFiber.subtreeFlags & Passive) {
+    let child = parentFiber.child;
+    while (child !== null) {
+      commitPassiveUnmountOnFiber(child);
+      child = child.sibling;
+    }
+  }
+}
+function commitHookPassiveUnmountEffects(finishedWork, nearestMountedAncestor, +hookFlags) {
+  commitHookEffectListUnmount(hookFlags, finishedWork, nearestMountedAncestor);
+}
+
+function commitHookEffectListUnmount(flags, finishedWork) {
+  const updateQueue = finishedWork.updateQueue;
+  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
+  if (lastEffect !== null) {
+    const firstEffect = lastEffect.next;
+    let effect = firstEffect;
+    do {
+      if ((effect.tag & flags) === flags) {
+        const destroy = effect.destroy;
+        effect.destroy = undefined;
+        if (destroy !== undefined) {
+          destroy();
+        }
+      }
+      effect = effect.next;
+    } while (effect !== firstEffect);
+  }
+}

+export function commitPassiveMountEffects(root, finishedWork) {
+  commitPassiveMountOnFiber(root, finishedWork);
+}
+function commitPassiveMountOnFiber(finishedRoot, finishedWork) {
+  const flags = finishedWork.flags;
+  switch (finishedWork.tag) {
+    case FunctionComponent: {
+      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
+      if (flags & Passive) {
+        commitHookPassiveMountEffects(finishedWork, HookPassive | HookHasEffect);
+      }
+      break;
+    }
+    case HostRoot: {
+      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
+      break;
+    }
+    default:
+      break;
+  }
+}
+function commitHookPassiveMountEffects(finishedWork, hookFlags) {
+  commitHookEffectListMount(hookFlags, finishedWork);
+}
+function commitHookEffectListMount(flags, finishedWork) {
+  const updateQueue = finishedWork.updateQueue;
+  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
+  if (lastEffect !== null) {
+    const firstEffect = lastEffect.next;
+    let effect = firstEffect;
+    do {
+      if ((effect.tag & flags) === flags) {
+        const create = effect.create;
+        effect.destroy = create();
+      }
+      effect = effect.next;
+    } while (effect !== firstEffect);
+  }
+}
+function recursivelyTraversePassiveMountEffects(root, parentFiber) {
+  if (parentFiber.subtreeFlags & Passive) {
+    let child = parentFiber.child;
+    while (child !== null) {
+      commitPassiveMountOnFiber(root, child);
+      child = child.sibling;
+    }
+  }
+}
let hostParent = null;
function commitDeletionEffects(root, returnFiber, deletedFiber) {
  let parent = returnFiber;
  findParent: while (parent !== null) {
    switch (parent.tag) {
      case HostComponent: {
        hostParent = parent.stateNode;
        break findParent;
      }
      case HostRoot: {
        hostParent = parent.stateNode.containerInfo;
        break findParent;
      }
      default:
        break;
    }
    parent = parent.return;
  }
  commitDeletionEffectsOnFiber(root, returnFiber, deletedFiber);
  hostParent = null;
}
function commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, deletedFiber) {
  switch (deletedFiber.tag) {
    case HostComponent:
    case HostText: {
      recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, deletedFiber);
      if (hostParent !== null) {
        removeChild(hostParent, deletedFiber.stateNode);
      }
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, parent) {
  let child = parent.child;
  while (child !== null) {
    commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, child);
    child = child.sibling;
  }
}
function recursivelyTraverseMutationEffects(root, parentFiber) {
  const deletions = parentFiber.deletions;
  if (deletions !== null) {
    for (let i = 0; i < deletions.length; i++) {
      const childToDelete = deletions[i];
      commitDeletionEffects(root, parentFiber, childToDelete);
    }
  }
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  const current = finishedWork.alternate;
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case HostRoot: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case FunctionComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case HostComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Update) {
        const instance = finishedWork.stateNode;
        if (instance != null) {
          const newProps = finishedWork.memoizedProps;
          const oldProps = current !== null ? current.memoizedProps : newProps;
          const type = finishedWork.type;
          const updatePayload = finishedWork.updateQueue;
          finishedWork.updateQueue = null;
          if (updatePayload !== null) {
            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
          }
        }
      }
      break;
    }
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

34.useLayoutEffect #

useLayoutEffect

34.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function Counter() {
  const [number, setNumber] = React.useState(0);
  React.useEffect(() => {
    console.log("useEffect1");
    return () => {
      console.log("destroy useEffect1");
    };
  });
+ React.useLayoutEffect(() => {
+   console.log("useLayoutEffect2");
+   return () => {
+     console.log("destroy useLayoutEffect2");
+   };
+ });
  React.useEffect(() => {
    console.log("useEffect3");
    return () => {
      console.log("destroy useEffect3");
    };
  });
  return (
    <div
      onClick={() => {
        setNumber(number + 1);
      }}
    >
      {number}
    </div>
  );
}
let element = <Counter />;
const root = createRoot(document.getElementById("root"));
root.render(element);

33.2 react\index.js #

src\react\index.js

export {
  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
  useReducer,
  useState,
  useEffect,
+ useLayoutEffect,
} from "./src/React";

34.3 React.js #

src\react\src\React.js

import { useReducer, useState, useEffect, useLayoutEffect } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";

export {
  useReducer,
  useState,
  useEffect,
+ useLayoutEffect,
  ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
};

34.4 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

export function useState(initialState) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

export function useEffect(create,deps) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useEffect(create,deps);
}
+export function useLayoutEffect(create,deps) {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useLayoutEffect(create,deps);
+}

34.5 ReactHookEffectTags.js #

src\react-reconciler\src\ReactHookEffectTags.js

export const HasEffect = 0b0001;
export const Passive = 0b1000;
+export const Layout = 0b0100;

34.6 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
export const Placement = 0b00000000000000000000000010;
export const Update = 0b00000000000000000000000100;
export const ChildDeletion = 0b00000000000000000000001000;
export const MutationMask = Placement | Update;
export const Passive = 0b00000000000000010000000000;
+export const LayoutMask = Update;

34.7 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
+import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
+import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
+ useLayoutEffect: mountLayoutEffect,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
+ useLayoutEffect: updateLayoutEffect,
};
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
+function updateLayoutEffect(create, deps) {
+  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
+}
+function mountLayoutEffect(create, deps) {
+  const fiberFlags = UpdateEffect;
+  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
+}
+function updateEffect(create, deps) {
+  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
+}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  const pendingQueue = queue.pending;
  let baseQueue = null;
  let newState = current.memoizedState;
  if (pendingQueue !== null) {
    baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    const first = baseQueue.next;
    let update = first;
    do {
      if (update.hasEagerState) {
        newState = update.eagerState;
      } else {
        const action = update.action;
        newState = reducer(newState, action);
      }
      update = update.next;
    } while (update !== null && update !== first);
  }
  hook.memoizedState = newState;
  queue.lastRenderedState = newState;
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const update = {
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const lastRenderedReducer = queue.lastRenderedReducer;
  const currentState = queue.lastRenderedState;
  const eagerState = lastRenderedReducer(currentState, action);
  update.hasEagerState = true;
  update.eagerState = eagerState;
  if (is(eagerState, currentState)) {
    return;
  }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
  workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

34.8 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import { scheduleCallback } from "scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Placement, Update, ChildDeletion, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
+  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import { FunctionComponent, IndeterminateComponent, HostRoot, HostComponent, HostText } from "./ReactWorkTags";

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  scheduleCallback(performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
  printFiber(finishedWork);
  console.log(`~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`);
  root.finishedWork = finishedWork;
  commitRoot(root);
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const { finishedWork } = root;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      scheduleCallback(flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
+   commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

function printFiber(fiber) {
  /*
  fiber.flags &= ~Forked;
  fiber.flags &= ~PlacementDEV;
  fiber.flags &= ~Snapshot;
  fiber.flags &= ~PerformedWork;
  */
  if (fiber.flags !== 0) {
    console.log(
      getFlags(fiber.flags),
      getTag(fiber.tag),
      typeof fiber.type === "function" ? fiber.type.name : fiber.type,
      fiber.memoizedProps
    );
    if (fiber.deletions) {
      for (let i = 0; i < fiber.deletions.length; i++) {
        const childToDelete = fiber.deletions[i];
        console.log(getTag(childToDelete.tag), childToDelete.type, childToDelete.memoizedProps);
      }
    }
  }
  let child = fiber.child;
  while (child) {
    printFiber(child);
    child = child.sibling;
  }
}
function getTag(tag) {
  switch (tag) {
    case FunctionComponent:
      return `FunctionComponent`;
    case HostRoot:
      return `HostRoot`;
    case HostComponent:
      return `HostComponent`;
    case HostText:
      return HostText;
    default:
      return tag;
  }
}
function getFlags(flags) {
  if (flags === (Update | Placement | ChildDeletion)) {
    return `自己移动和子元素有删除`;
  }
  if (flags === (ChildDeletion | Update)) {
    return `自己有更新和子元素有删除`;
  }
  if (flags === ChildDeletion) {
    return `子元素有删除`;
  }
  if (flags === (Placement | Update)) {
    return `移动并更新`;
  }
  if (flags === Placement) {
    return `插入`;
  }
  if (flags === Update) {
    return `更新`;
  }
  return flags;
}

34.9 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText, FunctionComponent } from "./ReactWorkTags";
+import { Passive, MutationMask, Placement, Update, LayoutMask } from "./ReactFiberFlags";
import { insertBefore, appendChild, commitUpdate, removeChild } from "react-dom-bindings/src/client/ReactDOMHostConfig";
+import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";

export function commitMutationEffects(finishedWork, root) {
  commitMutationEffectsOnFiber(finishedWork, root);
}
export function commitPassiveUnmountEffects(finishedWork) {
  commitPassiveUnmountOnFiber(finishedWork);
}
function commitPassiveUnmountOnFiber(finishedWork) {
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      if (finishedWork.flags & Passive) {
        commitHookPassiveUnmountEffects(finishedWork, finishedWork.return, HookPassive | HookHasEffect);
      }
      break;
    }
    default: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      break;
    }
  }
}
function recursivelyTraversePassiveUnmountEffects(parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveUnmountOnFiber(child);
      child = child.sibling;
    }
  }
}
function commitHookPassiveUnmountEffects(finishedWork, nearestMountedAncestor, hookFlags) {
  commitHookEffectListUnmount(hookFlags, finishedWork, nearestMountedAncestor);
}

function commitHookEffectListUnmount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const destroy = effect.destroy;
        effect.destroy = undefined;
        if (destroy !== undefined) {
          destroy();
        }
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}

export function commitPassiveMountEffects(root, finishedWork) {
  commitPassiveMountOnFiber(root, finishedWork);
}
function commitPassiveMountOnFiber(finishedRoot, finishedWork) {
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      if (flags & Passive) {
        commitHookPassiveMountEffects(finishedWork, HookPassive | HookHasEffect);
      }
      break;
    }
    case HostRoot: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      break;
    }
    default:
      break;
  }
}
function commitHookPassiveMountEffects(finishedWork, hookFlags) {
  commitHookEffectListMount(hookFlags, finishedWork);
}
function commitHookEffectListMount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const create = effect.create;
        effect.destroy = create();
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}
function recursivelyTraversePassiveMountEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveMountOnFiber(root, child);
      child = child.sibling;
    }
  }
}
let hostParent = null;
function commitDeletionEffects(root, returnFiber, deletedFiber) {
  let parent = returnFiber;
  findParent: while (parent !== null) {
    switch (parent.tag) {
      case HostComponent: {
        hostParent = parent.stateNode;
        break findParent;
      }
      case HostRoot: {
        hostParent = parent.stateNode.containerInfo;
        break findParent;
      }
      default:
        break;
    }
    parent = parent.return;
  }
  commitDeletionEffectsOnFiber(root, returnFiber, deletedFiber);
  hostParent = null;
}
function commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, deletedFiber) {
  switch (deletedFiber.tag) {
    case HostComponent:
    case HostText: {
      recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, deletedFiber);
      if (hostParent !== null) {
        removeChild(hostParent, deletedFiber.stateNode);
      }
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, parent) {
  let child = parent.child;
  while (child !== null) {
    commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, child);
    child = child.sibling;
  }
}
function recursivelyTraverseMutationEffects(root, parentFiber) {
  const deletions = parentFiber.deletions;
  if (deletions !== null) {
    for (let i = 0; i < deletions.length; i++) {
      const childToDelete = deletions[i];
      commitDeletionEffects(root, parentFiber, childToDelete);
    }
  }
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  const current = finishedWork.alternate;
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case HostRoot: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case FunctionComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
+     if (flags & Update) {
+       commitHookEffectListUnmount(HookLayout | HookHasEffect, finishedWork, finishedWork.return);
+     }
      break;
    }
    case HostComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Update) {
        const instance = finishedWork.stateNode;
        if (instance != null) {
          const newProps = finishedWork.memoizedProps;
          const oldProps = current !== null ? current.memoizedProps : newProps;
          const type = finishedWork.type;
          const updatePayload = finishedWork.updateQueue;
          finishedWork.updateQueue = null;
          if (updatePayload !== null) {
            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
          }
        }
      }
      break;
    }
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}

+export function commitLayoutEffects(finishedWork, root) {
+  const current = finishedWork.alternate;
+  commitLayoutEffectOnFiber(root, current, finishedWork);
+}
+function commitLayoutEffectOnFiber(finishedRoot, current, finishedWork) {
+  const flags = finishedWork.flags;
+  switch (finishedWork.tag) {
+    case FunctionComponent: {
+      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
+      if (flags & Update) {
+        commitHookLayoutEffects(finishedWork, HookLayout | HookHasEffect);
+      }
+      break;
+    }
+    case HostRoot: {
+      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
+      break;
+    }
+    default:
+      break;
+  }
+}
+function recursivelyTraverseLayoutEffects(root, parentFiber) {
+  if (parentFiber.subtreeFlags & LayoutMask) {
+    let child = parentFiber.child;
+    while (child !== null) {
+      const current = child.alternate;
+      commitLayoutEffectOnFiber(root, current, child);
+      child = child.sibling;
+    }
+  }
+}
+function commitHookLayoutEffects(finishedWork, hookFlags) {
+  commitHookEffectListMount(hookFlags, finishedWork);
+}

35.Scheduler_scheduleCallback #

35.1 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

+import { NormalPriority as NormalSchedulerPriority, scheduleCallback as Scheduler_scheduleCallback } from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Placement, Update, ChildDeletion, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import { FunctionComponent, IndeterminateComponent, HostRoot, HostComponent, HostText } from "./ReactWorkTags";

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
export function scheduleUpdateOnFiber(root) {
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
+ Scheduler_scheduleCallback(NormalSchedulerPriority, performConcurrentWorkOnRoot.bind(null, root));
}
function performConcurrentWorkOnRoot(root) {
  renderRootSync(root);
  const finishedWork = root.current.alternate;
  printFiber(finishedWork);
  console.log(`~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`);
  root.finishedWork = finishedWork;
  commitRoot(root);
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const { finishedWork } = root;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
+     Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root) {
  workInProgress = createWorkInProgress(root.current, null);
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root) {
  prepareFreshStack(root);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

function printFiber(fiber) {
  /*
  fiber.flags &= ~Forked;
  fiber.flags &= ~PlacementDEV;
  fiber.flags &= ~Snapshot;
  fiber.flags &= ~PerformedWork;
  */
  if (fiber.flags !== 0) {
    console.log(
      getFlags(fiber.flags),
      getTag(fiber.tag),
      typeof fiber.type === "function" ? fiber.type.name : fiber.type,
      fiber.memoizedProps
    );
    if (fiber.deletions) {
      for (let i = 0; i < fiber.deletions.length; i++) {
        const childToDelete = fiber.deletions[i];
        console.log(getTag(childToDelete.tag), childToDelete.type, childToDelete.memoizedProps);
      }
    }
  }
  let child = fiber.child;
  while (child) {
    printFiber(child);
    child = child.sibling;
  }
}
function getTag(tag) {
  switch (tag) {
    case FunctionComponent:
      return `FunctionComponent`;
    case HostRoot:
      return `HostRoot`;
    case HostComponent:
      return `HostComponent`;
    case HostText:
      return HostText;
    default:
      return tag;
  }
}
function getFlags(flags) {
  if (flags === (Update | Placement | ChildDeletion)) {
    return `自己移动和子元素有删除`;
  }
  if (flags === (ChildDeletion | Update)) {
    return `自己有更新和子元素有删除`;
  }
  if (flags === ChildDeletion) {
    return `子元素有删除`;
  }
  if (flags === (Placement | Update)) {
    return `移动并更新`;
  }
  if (flags === Placement) {
    return `插入`;
  }
  if (flags === Update) {
    return `更新`;
  }
  return flags;
}

35.2 Scheduler.js #

src\react-reconciler\src\Scheduler.js

import * as Scheduler from "scheduler";

export const scheduleCallback = Scheduler.unstable_scheduleCallback;
export const NormalPriority = Scheduler.unstable_NormalPriority;

35.3 Scheduler.js #

src\scheduler\src\forks\Scheduler.js

import {
  ImmediatePriority,
  UserBlockingPriority,
  NormalPriority,
  LowPriority,
  IdlePriority,
} from "../SchedulerPriorities";
import { push, pop, peek } from "../SchedulerMinHeap";
import { frameYieldMs } from "../SchedulerFeatureFlags";

const maxSigned31BitInt = 1073741823;
const IMMEDIATE_PRIORITY_TIMEOUT = -1;
const USER_BLOCKING_PRIORITY_TIMEOUT = 250;
const NORMAL_PRIORITY_TIMEOUT = 5000;
const LOW_PRIORITY_TIMEOUT = 10000;
const IDLE_PRIORITY_TIMEOUT = maxSigned31BitInt;

const taskQueue = [];
let taskIdCounter = 1;
let scheduledHostCallback = null;
let startTime = -1;
let currentTask = null;
const frameInterval = frameYieldMs;
const channel = new MessageChannel();
const port = channel.port2;

const getCurrentTime = () => performance.now();
channel.port1.onmessage = performWorkUntilDeadline;

function schedulePerformWorkUntilDeadline() {
  port.postMessage(null);
}
function performWorkUntilDeadline() {
  if (scheduledHostCallback !== null) {
    startTime = getCurrentTime();
    let hasMoreWork = true;
    try {
      hasMoreWork = scheduledHostCallback(startTime);
    } finally {
      if (hasMoreWork) {
        schedulePerformWorkUntilDeadline();
      } else {
        scheduledHostCallback = null;
      }
    }
  }
}
function requestHostCallback(callback) {
  scheduledHostCallback = callback;
  schedulePerformWorkUntilDeadline();
}

function unstable_scheduleCallback(priorityLevel, callback) {
  const currentTime = getCurrentTime();
  const startTime = currentTime;
  let timeout;
  switch (priorityLevel) {
    case ImmediatePriority:
      timeout = IMMEDIATE_PRIORITY_TIMEOUT;
      break;
    case UserBlockingPriority:
      timeout = USER_BLOCKING_PRIORITY_TIMEOUT;
      break;
    case IdlePriority:
      timeout = IDLE_PRIORITY_TIMEOUT;
      break;
    case LowPriority:
      timeout = LOW_PRIORITY_TIMEOUT;
      break;
    case NormalPriority:
    default:
      timeout = NORMAL_PRIORITY_TIMEOUT;
      break;
  }
  const expirationTime = startTime + timeout;
  const newTask = {
    id: taskIdCounter++,
    callback,
    priorityLevel,
    startTime,
    expirationTime,
    sortIndex: -1,
  };
  newTask.sortIndex = expirationTime;
  push(taskQueue, newTask);
  requestHostCallback(flushWork);
  return newTask;
}

function flushWork(initialTime) {
  return workLoop(initialTime);
}

function shouldYieldToHost() {
  const timeElapsed = getCurrentTime() - startTime;
  if (timeElapsed < frameInterval) {
    return false;
  }
  return true;
}
function workLoop(initialTime) {
  let currentTime = initialTime;
  currentTask = peek(taskQueue);
  while (currentTask !== null) {
    if (currentTask.expirationTime > currentTime && shouldYieldToHost()) {
      break;
    }
    const callback = currentTask.callback;
    if (typeof callback === "function") {
      currentTask.callback = null;
      const didUserCallbackTimeout = currentTask.expirationTime <= currentTime;
      const continuationCallback = callback(didUserCallbackTimeout);
      currentTime = getCurrentTime();
      if (typeof continuationCallback === "function") {
        currentTask.callback = continuationCallback;
        return true;
      }
      if (currentTask === peek(taskQueue)) {
        pop(taskQueue);
      }
    } else {
      pop(taskQueue);
    }
    currentTask = peek(taskQueue);
  }
  if (currentTask !== null) {
    return true;
  }
  return false;
}

export { NormalPriority as unstable_NormalPriority, unstable_scheduleCallback };

35.4 SchedulerFeatureFlags.js #

src\scheduler\src\SchedulerFeatureFlags.js

export const frameYieldMs = 5;

35.5 SchedulerMinHeap.js #

src\scheduler\src\SchedulerMinHeap.js

export function push(heap, node) {
  const index = heap.length;
  heap.push(node);
  siftUp(heap, node, index);
}
export function peek(heap) {
  return heap.length === 0 ? null : heap[0];
}
export function pop(heap) {
  if (heap.length === 0) {
    return null;
  }
  const first = heap[0];
  const last = heap.pop();
  if (last !== first) {
    heap[0] = last;
    siftDown(heap, last, 0);
  }
  return first;
}
function siftUp(heap, node, i) {
  let index = i;
  while (index > 0) {
    const parentIndex = (index - 1) >>> 1;
    const parent = heap[parentIndex];
    if (compare(parent, node) > 0) {
      heap[parentIndex] = node;
      heap[index] = parent;
      index = parentIndex;
    } else {
      return;
    }
  }
}
function siftDown(heap, node, i) {
  let index = i;
  const length = heap.length;
  const halfLength = length >>> 1;
  while (index < halfLength) {
    const leftIndex = (index + 1) * 2 - 1;
    const left = heap[leftIndex];
    const rightIndex = leftIndex + 1;
    const right = heap[rightIndex];
    if (compare(left, node) < 0) {
      if (rightIndex < length && compare(right, left) < 0) {
        heap[index] = right;
        heap[rightIndex] = node;
        index = rightIndex;
      } else {
        heap[index] = left;
        heap[leftIndex] = node;
        index = leftIndex;
      }
    } else if (rightIndex < length && compare(right, node) < 0) {
      heap[index] = right;
      heap[rightIndex] = node;
      index = rightIndex;
    } else {
      return;
    }
  }
}
function compare(a, b) {
  const diff = a.sortIndex - b.sortIndex;
  return diff !== 0 ? diff : a.id - b.id;
}

35.6 SchedulerPriorities.js #

src\scheduler\src\SchedulerPriorities.js

export const NoPriority = 0;
export const ImmediatePriority = 1;
export const UserBlockingPriority = 2;
export const NormalPriority = 3;
export const LowPriority = 4;
export const IdlePriority = 5;

36.初次渲染 #

36.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";
+let element = <h1>hello</h1>;
const root = createRoot(document.getElementById("root"));
root.render(element);

36.2 ReactFiberReconciler.js #

src\react-reconciler\src\ReactFiberReconciler.js

import { createFiberRoot } from "./ReactFiberRoot";
import { createUpdate, enqueueUpdate } from "./ReactFiberClassUpdateQueue";
+import { scheduleUpdateOnFiber, requestUpdateLane } from "./ReactFiberWorkLoop";
export function createContainer(containerInfo) {
  return createFiberRoot(containerInfo);
}
export function updateContainer(element, container) {
  const current = container.current;
+ const lane = requestUpdateLane(current);
+ const update = createUpdate(lane);
  update.payload = { element };
+ const root = enqueueUpdate(current, update, lane);
+ scheduleUpdateOnFiber(root, current, lane);
}

36.3 ReactFiberClassUpdateQueue.js #

src\react-reconciler\src\ReactFiberClassUpdateQueue.js

import assign from "shared/assign";
+import { enqueueConcurrentClassUpdate } from './ReactFiberConcurrentUpdates'
+import { mergeLanes, NoLanes, NoLane, isSubsetOfLanes } from './ReactFiberLane';

export const UpdateState = 0;
export function initializeUpdateQueue(fiber) {
  const queue = {
+   baseState: fiber.memoizedState,
+   firstBaseUpdate: null,
+   lastBaseUpdate: null,
    shared: {
      pending: null,
    },
  };
  fiber.updateQueue = queue;
}
+export function createUpdate(lane) {
+ const update = { tag: UpdateState, lane, next: null };
  return update;
}
+export function enqueueUpdate(fiber, update, lane) {
+  const updateQueue = fiber.updateQueue
+  const sharedQueue = updateQueue.shared
+  return enqueueConcurrentClassUpdate(fiber, sharedQueue, update, lane);
+}

function getStateFromUpdate(update, prevState, nextProps) {
  switch (update.tag) {
    case UpdateState: {
      const { payload } = update;
+     let partialState;
+     if (typeof payload === 'function') {
+       partialState = payload.call(null, prevState, nextProps);
+     } else {
+       partialState = payload;
+     }
+     return assign({}, prevState, partialState);
    }
    default:
      return prevState;
  }
}
+export const processUpdateQueue = (workInProgress, props, workInProgressRootRenderLanes) => {
+  // 获取新的更新队列
+  const queue = workInProgress.updateQueue
+  // 第一个跳过的更新
+  let firstBaseUpdate = queue.firstBaseUpdate;
+  // 最后一个跳过的更新
+  let lastBaseUpdate = queue.lastBaseUpdate;
+  // 获取待生效的队列
+  const pendingQueue = queue.shared.pending
+  /**   如果有新链表合并新旧链表开始  */
+  // 如果有新的待生效的队列
+  if (pendingQueue !== null) {
+    // 先清空待生效的队列
+    queue.shared.pending = null
+    // 最后一个待生效的更新
+    const lastPendingUpdate = pendingQueue
+    // 第一个待生效的更新
+    const firstPendingUpdate = lastPendingUpdate.next
+    // 把环状链表剪开
+    lastPendingUpdate.next = null
+    // 如果没有老的更新队列
+    if (lastBaseUpdate === null) {
+      // 第一个基本更新就是待生效队列的第一个更新
+      firstBaseUpdate = firstPendingUpdate;
+    } else {
+      // 否则把待生效更新队列添加到基本更新的尾部
+      lastBaseUpdate.next = firstPendingUpdate;
+    }
+    // 最后一个基本更新肯定就是最后一个待生效的更新
+    lastBaseUpdate = lastPendingUpdate;
+    /**  合并新旧链表结束  */
+  }
+
+  // 如果有更新
+  if (firstBaseUpdate !== null) {
+    // 基本状态
+    let newState = queue.baseState;
+    // 新的车道
+    let newLanes = NoLanes;
+    // 新的基本状态
+    let newBaseState = null;
+    // 新的第一个基本更新
+    let newFirstBaseUpdate = null;
+    // 新的最后一个基本更新 
+    let newLastBaseUpdate = null;
+    // 第一个更新
+    let update = firstBaseUpdate;
+    do {
+      const updateLane = update.lane;
+      const shouldSkipUpdate = !isSubsetOfLanes(workInProgressRootRenderLanes, updateLane);
+      // 判断优先级是否足够,如果不够就跳过此更新 
+      if (shouldSkipUpdate) {
+        // 复制一个新的更新并添加新的基本链表中
+        const clone = {
+          lane: updateLane,
+          tag: update.tag,
+          payload: update.payload,
+          next: null
+        };
+        if (newLastBaseUpdate === null) {
+          newFirstBaseUpdate = newLastBaseUpdate = clone;
+          newBaseState = newState;
+        } else {
+          newLastBaseUpdate = newLastBaseUpdate.next = clone;
+        }
+        // 保存此fiber上还剩下的更新车道
+        newLanes = mergeLanes(newLanes, updateLane);
+      } else {
+        // 如果已经有跳过的更新了，即使优先级足够也需要添到新的基本链表中
+        if (newLastBaseUpdate !== null) {
+          const clone = {
+            lane: NoLane,
+            tag: update.tag,
+            payload: update.payload,
+            next: null
+          };
+          newLastBaseUpdate = newLastBaseUpdate.next = clone;
+        }
+        // 根据更新计算新状态
+        newState = getStateFromUpdate(update, newState, props);
+        update = update.next;
+      }
+    } while (update);
+    // 如果没有跳过的更新
+    if (newLastBaseUpdate === null) {
+      newBaseState = newState;
+    }
+    queue.baseState = newBaseState;
+    queue.firstBaseUpdate = newFirstBaseUpdate;
+    queue.lastBaseUpdate = newLastBaseUpdate;
+    workInProgress.lanes = newLanes;
+    workInProgress.memoizedState = newState;
+  }
+}

+export function cloneUpdateQueue(current, workInProgress) {
+  const queue = workInProgress.updateQueue;
+  const currentQueue = current.updateQueue;
+  if (queue === currentQueue) {
+    const clone = {
+      baseState: currentQueue.baseState,
+      firstBaseUpdate: currentQueue.firstBaseUpdate,
+      lastBaseUpdate: currentQueue.lastBaseUpdate,
+      shared: currentQueue.shared,
+    };
+    workInProgress.updateQueue = clone;
+  }
+}

36.4 ReactFiberConcurrentUpdates.js #

src\react-reconciler\src\ReactFiberConcurrentUpdates.js

import { HostRoot } from "./ReactWorkTags";

const concurrentQueues = [];
let concurrentQueuesIndex = 0;

export function markUpdateLaneFromFiberToRoot(sourceFiber) {
  let node = sourceFiber;
  let parent = sourceFiber.return;
  while (parent !== null) {
    node = parent;
    parent = parent.return;
  }
  if (node.tag === HostRoot) {
    const root = node.stateNode;
    return root;
  }
  return null;
}
export function enqueueConcurrentHookUpdate(fiber, queue, update) {
  enqueueUpdate(fiber, queue, update);
  return getRootForUpdatedFiber(fiber);
}
+export function enqueueConcurrentClassUpdate(fiber, queue, update, lane) {
+  enqueueUpdate(fiber, queue, update, lane);
+  return getRootForUpdatedFiber(fiber);
+}

+function enqueueUpdate(fiber, queue, update, lane) {
  concurrentQueues[concurrentQueuesIndex++] = fiber;
  concurrentQueues[concurrentQueuesIndex++] = queue;
  concurrentQueues[concurrentQueuesIndex++] = update;
+ concurrentQueues[concurrentQueuesIndex++] = lane;
}
function getRootForUpdatedFiber(sourceFiber) {
  let node = sourceFiber;
  let parent = node.return;
  while (parent !== null) {
    node = parent;
    parent = node.return;
  }
  return node.tag === HostRoot ? node.stateNode : null;
}

export function finishQueueingConcurrentUpdates() {
  const endIndex = concurrentQueuesIndex;
  concurrentQueuesIndex = 0;
  let i = 0;
  while (i < endIndex) {
    const fiber = concurrentQueues[i++];
    const queue = concurrentQueues[i++];
    const update = concurrentQueues[i++];
+   const lane = concurrentQueues[i++]
    if (queue !== null && update !== null) {
      const pending = queue.pending;
      if (pending === null) {
        update.next = update;
      } else {
        update.next = pending.next;
        pending.next = update;
      }
      queue.pending = update;
    }
  }
}

36.5 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

+import {
+  scheduleCallback as Scheduler_scheduleCallback,
+  ImmediatePriority as ImmediateSchedulerPriority,
+  UserBlockingPriority as UserBlockingSchedulerPriority,
+  NormalPriority as NormalSchedulerPriority,
+  IdlePriority as IdleSchedulerPriority,
+} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
+import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
+import {
+  NoLane, markRootUpdated, NoLanes,
+  getNextLanes, getHighestPriorityLane, SyncLane,
+  includesBlockingLane
+} from './ReactFiberLane';
+import {
+  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
+  DefaultEventPriority, IdleEventPriority,
+} from './ReactEventPriorities';
+import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';


let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
+let workInProgressRootRenderLanes = NoLanes;

+export function scheduleUpdateOnFiber(root, fiber, lane) {
+ markRootUpdated(root, lane);
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
+ const nextLanes = getNextLanes(root, NoLanes);
+ const newCallbackPriority = getHighestPriorityLane(nextLanes);
+ if (newCallbackPriority === SyncLane) {
+   // TODO
+ } else {
+   let schedulerPriorityLevel;
+   switch (lanesToEventPriority(nextLanes)) {
+     case DiscreteEventPriority:
+       schedulerPriorityLevel = ImmediateSchedulerPriority;
+       break;
+     case ContinuousEventPriority:
+       schedulerPriorityLevel = UserBlockingSchedulerPriority;
+       break;
+     case DefaultEventPriority:
+       schedulerPriorityLevel = NormalSchedulerPriority;
+       break;
+     case IdleEventPriority:
+       schedulerPriorityLevel = IdleSchedulerPriority;
+       break;
+     default:
+       schedulerPriorityLevel = NormalSchedulerPriority;
+       break;
+   }
+   Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
}
+function performConcurrentWorkOnRoot(root,didTimeout) {
+ const lanes = getNextLanes(root, NoLanes);
+ if (lanes === NoLanes) {
+   return null;
+ }
+ const shouldTimeSlice = !includesBlockingLane(root, lanes) && (!didTimeout);
+ if (shouldTimeSlice) {
+   renderRootConcurrent(root, lanes)
+ } else {
+   renderRootSync(root, lanes);
+ }
  const finishedWork = root.current.alternate;
  root.finishedWork = finishedWork;
  commitRoot(root);
}
+function renderRootConcurrent(root, lanes) {
+  console.log(root, lanes);
+}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const { finishedWork } = root;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
+function prepareFreshStack(root, lanes) {
  workInProgress = createWorkInProgress(root.current, null);
+ workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
+function renderRootSync(root, lanes) {
+ prepareFreshStack(root, lanes);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
+ const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

+export function requestUpdateLane() {
+  const updateLane = getCurrentUpdatePriority();
+  if (updateLane !== NoLane) {
+    return updateLane;
+  }
+  const eventLane = getCurrentEventPriority();
+  return eventLane;
+}

36.6 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import { HostRoot, HostComponent, HostText, IndeterminateComponent, FunctionComponent } from "./ReactWorkTags";
+import { processUpdateQueue, cloneUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { renderWithHooks } from "react-reconciler/src/ReactFiberHooks";

function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(workInProgress, current.child, nextChildren);
  }
}
+function updateHostRoot(current, workInProgress, renderLanes) {
+ const nextProps = workInProgress.pendingProps;
+ cloneUpdateQueue(current, workInProgress);
+ processUpdateQueue(workInProgress, nextProps, renderLanes)
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function mountIndeterminateComponent(_current, workInProgress, Component) {
  const props = workInProgress.pendingProps;
  const value = renderWithHooks(null, workInProgress, Component, props);
  workInProgress.tag = FunctionComponent;
  reconcileChildren(null, workInProgress, value);
  return workInProgress.child;
}
function updateFunctionComponent(current, workInProgress, Component, nextProps,workInProgressRootRenderLanes) {
  const nextChildren = renderWithHooks(current, workInProgress, Component, nextProps,workInProgressRootRenderLanes);
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
+export function beginWork(current, workInProgress, renderLanes) {
  switch (workInProgress.tag) {
    case IndeterminateComponent: {
+     return mountIndeterminateComponent(current, workInProgress, workInProgress.type, renderLanes);
    }
    case FunctionComponent: {
      const Component = workInProgress.type;
      const resolvedProps = workInProgress.pendingProps;
+     return updateFunctionComponent(current, workInProgress, Component, resolvedProps, renderLanes);
    }
    case HostRoot:
+     return updateHostRoot(current, workInProgress, renderLanes);
    case HostComponent:
+     return updateHostComponent(current, workInProgress, renderLanes);
    case HostText:
    default:
      return null;
  }
}

36.7 ReactFiberLane.js #

src\react-reconciler\src\ReactFiberLane.js

export const TotalLanes = 31;
export const NoLanes = 0b0000000000000000000000000000000;
export const NoLane = 0b0000000000000000000000000000000;
export const SyncLane = 0b0000000000000000000000000000001;// 1
export const InputContinuousLane = 0b0000000000000000000000000000100;// 4
export const DefaultLane = 0b0000000000000000000000000010000;// 16
export const NonIdleLanes = 0b0001111111111111111111111111111;
export const IdleLane = 0b0100000000000000000000000000000;

export function mergeLanes(a, b) {
  return a | b;
}
export function markRootUpdated(root, updateLane) {
  root.pendingLanes |= updateLane;
}

export function getNextLanes(root) {
  const pendingLanes = root.pendingLanes;
  if (pendingLanes === NoLanes) {
    return NoLanes;
  }
  const nextLanes = getHighestPriorityLanes(pendingLanes);
  return nextLanes;
}

function getHighestPriorityLanes(lanes) {
  return getHighestPriorityLane(lanes);
}

export function getHighestPriorityLane(lanes) {
  return lanes & -lanes;
}

export function includesNonIdleWork(lanes) {
  return (lanes & NonIdleLanes) !== NoLanes;
}
export function includesBlockingLane(root, lanes) {
  const SyncDefaultLanes = InputContinuousLane | DefaultLane;
  return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function isSubsetOfLanes(set, subset) {
  return (set & subset) === subset;
}

36.8 ReactEventPriorities.js #

src\react-reconciler\src\ReactEventPriorities.js

import {
  NoLane, DefaultLane, getHighestPriorityLane,
  includesNonIdleWork, SyncLane, InputContinuousLane, IdleLane
} from './ReactFiberLane';

export const DefaultEventPriority = DefaultLane;
export const DiscreteEventPriority = SyncLane;
export const ContinuousEventPriority = InputContinuousLane;
export const IdleEventPriority = IdleLane;

let currentUpdatePriority = NoLane;

export function getCurrentUpdatePriority() {
  return currentUpdatePriority;
}
export function setCurrentUpdatePriority(newPriority) {
  currentUpdatePriority = newPriority;
}
export function isHigherEventPriority(a, b) {
  return a !== 0 && a < b;
}
export function lanesToEventPriority(lanes) {
  const lane = getHighestPriorityLane(lanes);
  if (!isHigherEventPriority(DiscreteEventPriority, lane)) {
    return DiscreteEventPriority;
  }
  if (!isHigherEventPriority(ContinuousEventPriority, lane)) {
    return ContinuousEventPriority;
  }
  if (includesNonIdleWork(lane)) {
    return DefaultEventPriority;
  }
  return IdleEventPriority;
}

36.9 ReactDOMHostConfig.js #

src\react-dom-bindings\src\client\ReactDOMHostConfig.js

import { setInitialProperties, diffProperties, updateProperties } from "./ReactDOMComponent";
import { precacheFiberNode, updateFiberProps } from "./ReactDOMComponentTree";
+import { getEventPriority } from '../events/ReactDOMEventListener';
+import { DefaultEventPriority } from 'react-reconciler/src/ReactEventPriorities';

export function shouldSetTextContent(type, props) {
  return typeof props.children === "string" || typeof props.children === "number";
}
export const appendInitialChild = (parent, child) => {
  parent.appendChild(child);
};
export const createInstance = (type, props, internalInstanceHandle) => {
  const domElement = document.createElement(type);
  precacheFiberNode(internalInstanceHandle, domElement);
  updateFiberProps(domElement, props);
  return domElement;
};
export const createTextInstance = (content) => document.createTextNode(content);
export function finalizeInitialChildren(domElement, type, props) {
  setInitialProperties(domElement, type, props);
}
export function appendChild(parentInstance, child) {
  parentInstance.appendChild(child);
}
export function insertBefore(parentInstance, child, beforeChild) {
  parentInstance.insertBefore(child, beforeChild);
}

export function prepareUpdate(domElement, type, oldProps, newProps) {
  return diffProperties(domElement, type, oldProps, newProps);
}

export function commitUpdate(domElement, updatePayload, type, oldProps, newProps) {
  updateProperties(domElement, updatePayload, type, oldProps, newProps);
  updateFiberProps(domElement, newProps);
}
export function removeChild(parentInstance, child) {
  parentInstance.removeChild(child);
}
+export function getCurrentEventPriority() {
+  const currentEvent = window.event;
+  if (currentEvent === undefined) {
+    return DefaultEventPriority;
+  }
+  return getEventPriority(currentEvent.type);
+}

36.10 ReactDOMEventListener.js #

src\react-dom-bindings\src\events\ReactDOMEventListener.js

import getEventTarget from "./getEventTarget";
import { getClosestInstanceFromNode } from "../client/ReactDOMComponentTree";
import { dispatchEventForPluginEventSystem } from "./DOMPluginEventSystem";
+import { DiscreteEventPriority, ContinuousEventPriority, DefaultEventPriority } from 'react-reconciler/src/ReactEventPriorities';

export function createEventListenerWrapperWithPriority(
  targetContainer,
  domEventName,
  eventSystemFlags
) {
  const listenerWrapper = dispatchDiscreteEvent;
  return listenerWrapper.bind(null, domEventName, eventSystemFlags, targetContainer);
}
function dispatchDiscreteEvent(domEventName, eventSystemFlags, container, nativeEvent) {
  dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent);
}
export function dispatchEvent(domEventName, eventSystemFlags, targetContainer, nativeEvent) {
  const nativeEventTarget = getEventTarget(nativeEvent);
  const targetInst = getClosestInstanceFromNode(nativeEventTarget);
  dispatchEventForPluginEventSystem(
    domEventName,
    eventSystemFlags,
    nativeEvent,
    targetInst,
    targetContainer
  );
}
+export function getEventPriority(domEventName) {
+  switch (domEventName) {
+    case 'click':
+      return DiscreteEventPriority;
+    case 'drag':
+      return ContinuousEventPriority;
+    default:
+      return DefaultEventPriority;
+  }
+}

36.11 Scheduler.js #

src\react-reconciler\src\Scheduler.js

import * as Scheduler from 'scheduler'

export const scheduleCallback = Scheduler.unstable_scheduleCallback
export const NormalPriority = Scheduler.unstable_NormalPriority
+export const ImmediatePriority = Scheduler.unstable_ImmediatePriority;
+export const UserBlockingPriority = Scheduler.unstable_UserBlockingPriority;
+export const LowPriority = Scheduler.unstable_LowPriority;
+export const IdlePriority = Scheduler.unstable_IdlePriority;

37.更新渲染 #

37.1 main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";
+function FunctionComponent() {
+  const [number, setNumber] = React.useState(0);
+  return <button onClick={() => {
+    setNumber(number + 1)
+  }}>{number}</button>
+}
const element = <FunctionComponent />;
const container = document.getElementById("root");
const root = createRoot(container);
root.render(element);

37.2 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
+import { scheduleUpdateOnFiber, requestUpdateLane } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
  useLayoutEffect: mountLayoutEffect,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
  useLayoutEffect: updateLayoutEffect,
};
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
function updateLayoutEffect(create, deps) {
  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
}
function mountLayoutEffect(create, deps) {
  const fiberFlags = UpdateEffect;
  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
}
function updateEffect(create, deps) {
  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  const pendingQueue = queue.pending;
  let baseQueue = null;
  let newState = current.memoizedState;
  if (pendingQueue !== null) {
    baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    const first = baseQueue.next;
    let update = first;
    do {
      if (update.hasEagerState) {
        newState = update.eagerState;
      } else {
        const action = update.action;
        newState = reducer(newState, action);
      }
      update = update.next;
    } while (update !== null && update !== first);
  }
  hook.memoizedState = newState;
  queue.lastRenderedState = newState;
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
+ const lane = requestUpdateLane(fiber);
  const update = {
+   lane,
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const lastRenderedReducer = queue.lastRenderedReducer;
  const currentState = queue.lastRenderedState;
  const eagerState = lastRenderedReducer(currentState, action);
  update.hasEagerState = true;
  update.eagerState = eagerState;
  if (is(eagerState, currentState)) {
    return;
  }
+ const root = enqueueConcurrentHookUpdate(fiber, queue, update, lane);
+ scheduleUpdateOnFiber(root, fiber, lane);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}
export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
  workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

37.3 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import {
  scheduleCallback as Scheduler_scheduleCallback,
  ImmediatePriority as ImmediateSchedulerPriority,
  UserBlockingPriority as UserBlockingSchedulerPriority,
  NormalPriority as NormalSchedulerPriority,
  IdlePriority as IdleSchedulerPriority,
} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import {
  NoLane, markRootUpdated, NoLanes,
  getNextLanes, getHighestPriorityLane, SyncLane,
  includesBlockingLane
} from './ReactFiberLane';
import {
  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
+ DefaultEventPriority, IdleEventPriority, setCurrentUpdatePriority
} from './ReactEventPriorities';
import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';
+import { scheduleSyncCallback, flushSyncCallbacks } from './ReactFiberSyncTaskQueue';

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
let workInProgressRootRenderLanes = NoLanes;

export function scheduleUpdateOnFiber(root, fiber, lane) {
  markRootUpdated(root, lane);
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  const nextLanes = getNextLanes(root, NoLanes);
  const newCallbackPriority = getHighestPriorityLane(nextLanes);
  if (newCallbackPriority === SyncLane) {
+   scheduleSyncCallback(performSyncWorkOnRoot.bind(null, root));
+   queueMicrotask(flushSyncCallbacks);
  } else {
    let schedulerPriorityLevel;
    switch (lanesToEventPriority(nextLanes)) {
      case DiscreteEventPriority:
        schedulerPriorityLevel = ImmediateSchedulerPriority;
        break;
      case ContinuousEventPriority:
        schedulerPriorityLevel = UserBlockingSchedulerPriority;
        break;
      case DefaultEventPriority:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
      case IdleEventPriority:
        schedulerPriorityLevel = IdleSchedulerPriority;
        break;
      default:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
    }
    Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
}
+function performSyncWorkOnRoot(root) {
+  const lanes = getNextLanes(root, NoLanes);
+  renderRootSync(root, lanes);
+  const finishedWork = root.current.alternate
+  root.finishedWork = finishedWork
+  commitRoot(root)
+  return null;//如果没有任务了一定要返回null
+}
function performConcurrentWorkOnRoot(root) {
  const lanes = getNextLanes(root, NoLanes);
  if (lanes === NoLanes) {
    return null;
  }
  const shouldTimeSlice = !includesBlockingLane(root, lanes) && (!didTimeout);
  if (shouldTimeSlice) {
    renderRootConcurrent(root, lanes)
  } else {
    renderRootSync(root, lanes);
  }
  const finishedWork = root.current.alternate;
  root.finishedWork = finishedWork;
  commitRoot(root);
}
function renderRootConcurrent(root, lanes) {
  console.log(root, lanes);
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
+function commitRoot(root) {
+  const previousPriority = getCurrentUpdatePriority();
+  try {
+    setCurrentUpdatePriority(DiscreteEventPriority);
+    commitRootImpl(root);
+  } finally {
+    setCurrentUpdatePriority(previousPriority);
+  }
+}
+function commitRootImpl(root) {
  const { finishedWork } = root;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
+}
function prepareFreshStack(root, lanes) {
  workInProgress = createWorkInProgress(root.current, null);
  workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root, lanes) {
  prepareFreshStack(root, lanes);
  workLoopSync();
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
}

export function requestUpdateLane() {
  const updateLane = getCurrentUpdatePriority();
  if (updateLane !== NoLane) {
    return updateLane;
  }
  const eventLane = getCurrentEventPriority();
  return eventLane;
}

37.4 ReactFiberSyncTaskQueue.js #

src\react-reconciler\src\ReactFiberSyncTaskQueue.js

import { DiscreteEventPriority, getCurrentUpdatePriority, setCurrentUpdatePriority } from './ReactEventPriorities';

let syncQueue = null;
let isFlushingSyncQueue = false;

export function scheduleSyncCallback(callback) {
  if (syncQueue === null) {
    syncQueue = [callback];
  } else {
    syncQueue.push(callback);
  }
}

export function flushSyncCallbacks() {
  if (!isFlushingSyncQueue && syncQueue !== null) {
    isFlushingSyncQueue = true;
    let i = 0;
    const previousUpdatePriority = getCurrentUpdatePriority();
    try {
      const isSync = true;
      const queue = syncQueue;
      setCurrentUpdatePriority(DiscreteEventPriority);
      for (; i < queue.length; i++) {
        let callback = queue[i];
        do {
          callback = callback(isSync);
        } while (callback !== null);
      }
      syncQueue = null;
    } finally {
      setCurrentUpdatePriority(previousUpdatePriority);
      isFlushingSyncQueue = false;
    }
  }
  return null;
}

37.5 ReactFiberConcurrentUpdates.js #

src\react-reconciler\src\ReactFiberConcurrentUpdates.js

import { HostRoot } from "./ReactWorkTags";

const concurrentQueues = [];
let concurrentQueuesIndex = 0;

export function markUpdateLaneFromFiberToRoot(sourceFiber) {
  let node = sourceFiber;
  let parent = sourceFiber.return;
  while (parent !== null) {
    node = parent;
    parent = parent.return;
  }
  if (node.tag === HostRoot) {
    const root = node.stateNode;
    return root;
  }
  return null;
}
+export function enqueueConcurrentHookUpdate(fiber, queue, update, lane) {
+ enqueueUpdate(fiber, queue, update, lane);
  return getRootForUpdatedFiber(fiber);
}
export function enqueueConcurrentClassUpdate(fiber, queue, update, lane) {
  enqueueUpdate(fiber, queue, update, lane);
  return getRootForUpdatedFiber(fiber);
}

function enqueueUpdate(fiber, queue, update, lane) {
  concurrentQueues[concurrentQueuesIndex++] = fiber;
  concurrentQueues[concurrentQueuesIndex++] = queue;
  concurrentQueues[concurrentQueuesIndex++] = update;
  concurrentQueues[concurrentQueuesIndex++] = lane;
}
function getRootForUpdatedFiber(sourceFiber) {
  let node = sourceFiber;
  let parent = node.return;
  while (parent !== null) {
    node = parent;
    parent = node.return;
  }
  return node.tag === HostRoot ? node.stateNode : null;
}

export function finishQueueingConcurrentUpdates() {
  const endIndex = concurrentQueuesIndex;
  concurrentQueuesIndex = 0;
  let i = 0;
  while (i < endIndex) {
    const fiber = concurrentQueues[i++];
    const queue = concurrentQueues[i++];
    const update = concurrentQueues[i++];
    const lane = concurrentQueues[i++]
    if (queue !== null && update !== null) {
      const pending = queue.pending;
      if (pending === null) {
        update.next = update;
      } else {
        update.next = pending.next;
        pending.next = update;
      }
      queue.pending = update;
    }
  }
}

37.6 ReactDOMEventListener.js #

src\react-dom-bindings\src\events\ReactDOMEventListener.js

import getEventTarget from "./getEventTarget";
import { getClosestInstanceFromNode } from "../client/ReactDOMComponentTree";
import { dispatchEventForPluginEventSystem } from "./DOMPluginEventSystem";
import {
  DiscreteEventPriority, ContinuousEventPriority, DefaultEventPriority,
+ getCurrentUpdatePriority, setCurrentUpdatePriority
} from 'react-reconciler/src/ReactEventPriorities';

export function createEventListenerWrapperWithPriority(
  targetContainer,
  domEventName,
  eventSystemFlags
) {
  const listenerWrapper = dispatchDiscreteEvent;
  return listenerWrapper.bind(null, domEventName, eventSystemFlags, targetContainer);
}
+function dispatchDiscreteEvent(domEventName, eventSystemFlags, container, nativeEvent) {
+  const previousPriority = getCurrentUpdatePriority();
+  try {
+    setCurrentUpdatePriority(DiscreteEventPriority);
     dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent)
+  } finally {
+    setCurrentUpdatePriority(previousPriority);
+  }
+}
export function dispatchEvent(domEventName, eventSystemFlags, targetContainer, nativeEvent) {
  const nativeEventTarget = getEventTarget(nativeEvent);
  const targetInst = getClosestInstanceFromNode(nativeEventTarget);
  dispatchEventForPluginEventSystem(
    domEventName,
    eventSystemFlags,
    nativeEvent,
    targetInst,
    targetContainer
  );
}


export function getEventPriority(domEventName) {
  switch (domEventName) {
    case 'click':
      return DiscreteEventPriority;
    case 'drag':
      return ContinuousEventPriority;
    default:
      return DefaultEventPriority;
  }
}

38.并发渲染 #

38.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

+function FunctionComponent() {
+  console.log('FunctionComponent');
+  const [number, setNumber] = React.useState(0);
+  React.useEffect(() => {
+    setNumber(number => number + 1)
+  }, []);
+  return (<button onClick={() => setNumber(number + 1)}>{number}</button>)
+}
const element = <FunctionComponent />;
const container = document.getElementById("root");
const root = createRoot(container, { unstable_concurrentUpdatesByDefault: true });
root.render(element);

38.2 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import {
  scheduleCallback as Scheduler_scheduleCallback,
  ImmediatePriority as ImmediateSchedulerPriority,
  UserBlockingPriority as UserBlockingSchedulerPriority,
  NormalPriority as NormalSchedulerPriority,
  IdlePriority as IdleSchedulerPriority,
+ shouldYield
} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import {
  NoLane, markRootUpdated, NoLanes,
  getNextLanes, getHighestPriorityLane, SyncLane,
  includesBlockingLane
} from './ReactFiberLane';
import {
  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
  DefaultEventPriority, IdleEventPriority, setCurrentUpdatePriority
} from './ReactEventPriorities';
import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';
import { scheduleSyncCallback, flushSyncCallbacks } from './ReactFiberSyncTaskQueue';

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
let workInProgressRootRenderLanes = NoLanes;

+const RootInProgress = 0;
+const RootCompleted = 5;
+let workInProgressRoot = null;
+let workInProgressRootExitStatus = RootInProgress;

export function scheduleUpdateOnFiber(root, fiber, lane) {
  markRootUpdated(root, lane);
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  const nextLanes = getNextLanes(root, NoLanes);
+ if (nextLanes === NoLanes) {
+   root.callbackNode = null;
+   root.callbackPriority = NoLane;
+   return;
+ }
  const newCallbackPriority = getHighestPriorityLane(nextLanes);
+ let newCallbackNode;
  if (newCallbackPriority === SyncLane) {
    scheduleSyncCallback(performSyncWorkOnRoot.bind(null, root));
    queueMicrotask(flushSyncCallbacks);
+   newCallbackNode = null;
  } else {
    let schedulerPriorityLevel;
    switch (lanesToEventPriority(nextLanes)) {
      case DiscreteEventPriority:
        schedulerPriorityLevel = ImmediateSchedulerPriority;
        break;
      case ContinuousEventPriority:
        schedulerPriorityLevel = UserBlockingSchedulerPriority;
        break;
      case DefaultEventPriority:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
      case IdleEventPriority:
        schedulerPriorityLevel = IdleSchedulerPriority;
        break;
      default:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
    }
+   newCallbackNode = Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
+ root.callbackNode = newCallbackNode;
}
function performSyncWorkOnRoot(root) {
  const lanes = getNextLanes(root, NoLanes);
  renderRootSync(root, lanes);
  const finishedWork = root.current.alternate
  root.finishedWork = finishedWork
  commitRoot(root)
  return null;
}
function performConcurrentWorkOnRoot(root, didTimeout) {
+ const originalCallbackNode = root.callbackNode;
  const lanes = getNextLanes(root, NoLanes);
  if (lanes === NoLanes) {
    return null;
  }
  const shouldTimeSlice = !includesBlockingLane(root, lanes) && (!didTimeout);
+ const exitStatus = shouldTimeSlice ? renderRootConcurrent(root, lanes) : renderRootSync(root, lanes);
+ if (exitStatus !== RootInProgress) {
+   const finishedWork = root.current.alternate
+   root.finishedWork = finishedWork
+   commitRoot(root)
+ }
+ if (root.callbackNode === originalCallbackNode) {
+   return performConcurrentWorkOnRoot.bind(null, root);
+ }
+ return null;
}
function renderRootConcurrent(root, lanes) {
+ if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
+   prepareFreshStack(root, lanes);
+ }
+ workLoopConcurrent();
+ if (workInProgress !== null) {
+   return RootInProgress;
+ }
+ workInProgressRoot = null;
+ workInProgressRootRenderLanes = NoLanes;
+ return workInProgressRootExitStatus;
}
+function workLoopConcurrent() {
+  sleep(6);
+  performUnitOfWork(workInProgress);
+  console.log('shouldYield()', shouldYield(), workInProgress?.type);
+}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const previousPriority = getCurrentUpdatePriority();
  try {
    setCurrentUpdatePriority(DiscreteEventPriority);
    commitRootImpl(root);
  } finally {
    setCurrentUpdatePriority(previousPriority);
  }
}
function commitRootImpl(root) {
  const { finishedWork } = root;
+ root.callbackNode = null;
+ root.callbackPriority = NoLane;
+ workInProgressRoot = null;
+ workInProgressRootRenderLanes = NoLanes;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root, lanes) {
+ workInProgressRoot = root;
  workInProgress = createWorkInProgress(root.current, null);
  workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root, lanes) {
+ //不是一个根，或者是更高优先级的更新
+ if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes)
+ }
  workLoopSync();
+ return workInProgressRootExitStatus;
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
+ if (workInProgressRootExitStatus === RootInProgress) {
+   workInProgressRootExitStatus = RootCompleted;
+ }
}

export function requestUpdateLane() {
  const updateLane = getCurrentUpdatePriority();
  if (updateLane !== NoLane) {
    return updateLane;
  }
  const eventLane = getCurrentEventPriority();
  return eventLane;
}

+function sleep(time) {
+  const timeStamp = new Date().getTime();
+  const endTime = timeStamp + time;
+  while (true) {
+    if (new Date().getTime() > endTime) {
+      return;
+    }
+  }
+}

38.3 Scheduler.js #

src\react-reconciler\src\Scheduler.js

import * as Scheduler from 'scheduler'
export const scheduleCallback = Scheduler.unstable_scheduleCallback
export const NormalPriority = Scheduler.unstable_NormalPriority
export const ImmediatePriority = Scheduler.unstable_ImmediatePriority;
export const UserBlockingPriority = Scheduler.unstable_UserBlockingPriority;
export const LowPriority = Scheduler.unstable_LowPriority;
export const IdlePriority = Scheduler.unstable_IdlePriority;
+export const shouldYield = Scheduler.unstable_shouldYield

38.4 Scheduler.js #

src\scheduler\src\forks\Scheduler.js

import {
  ImmediatePriority,
  UserBlockingPriority,
  NormalPriority,
  LowPriority,
  IdlePriority,
} from "../SchedulerPriorities";
import { push, pop, peek } from "../SchedulerMinHeap";
import { frameYieldMs } from "../SchedulerFeatureFlags";

const maxSigned31BitInt = 1073741823;
const IMMEDIATE_PRIORITY_TIMEOUT = -1;
const USER_BLOCKING_PRIORITY_TIMEOUT = 250;
const NORMAL_PRIORITY_TIMEOUT = 5000;
const LOW_PRIORITY_TIMEOUT = 10000;
const IDLE_PRIORITY_TIMEOUT = maxSigned31BitInt;

const taskQueue = [];
let taskIdCounter = 1;
let scheduledHostCallback = null;
let startTime = -1;
let currentTask = null;
const frameInterval = frameYieldMs;
const channel = new MessageChannel();
const port = channel.port2;

const getCurrentTime = () => performance.now();
channel.port1.onmessage = performWorkUntilDeadline;

function schedulePerformWorkUntilDeadline() {
  port.postMessage(null);
}
function performWorkUntilDeadline() {
  if (scheduledHostCallback !== null) {
    startTime = getCurrentTime();
    let hasMoreWork = true;
    try {
      hasMoreWork = scheduledHostCallback(startTime);
    } finally {
      if (hasMoreWork) {
        schedulePerformWorkUntilDeadline();
      } else {
        scheduledHostCallback = null;
      }
    }
  }
}
function requestHostCallback(callback) {
  scheduledHostCallback = callback;
  schedulePerformWorkUntilDeadline();
}

function unstable_scheduleCallback(priorityLevel, callback) {
  const currentTime = getCurrentTime();
  const startTime = currentTime;
  let timeout;
  switch (priorityLevel) {
    case ImmediatePriority:
      timeout = IMMEDIATE_PRIORITY_TIMEOUT;
      break;
    case UserBlockingPriority:
      timeout = USER_BLOCKING_PRIORITY_TIMEOUT;
      break;
    case IdlePriority:
      timeout = IDLE_PRIORITY_TIMEOUT;
      break;
    case LowPriority:
      timeout = LOW_PRIORITY_TIMEOUT;
      break;
    case NormalPriority:
    default:
      timeout = NORMAL_PRIORITY_TIMEOUT;
      break;
  }
  const expirationTime = startTime + timeout;
  const newTask = {
    id: taskIdCounter++,
    callback,
    priorityLevel,
    startTime,
    expirationTime,
    sortIndex: -1,
  };
  newTask.sortIndex = expirationTime;
  push(taskQueue, newTask);
  requestHostCallback(flushWork);
  return newTask;
}

function flushWork(initialTime) {
  return workLoop(initialTime);
}

function shouldYieldToHost() {
  const timeElapsed = getCurrentTime() - startTime;
  if (timeElapsed < frameInterval) {
    return false;
  }
  return true;
}
function workLoop(initialTime) {
  let currentTime = initialTime;
  currentTask = peek(taskQueue);
  while (currentTask !== null) {
    if (currentTask.expirationTime > currentTime && shouldYieldToHost()) {
      break;
    }
    const callback = currentTask.callback;
    if (typeof callback === "function") {
      currentTask.callback = null;
      const didUserCallbackTimeout = currentTask.expirationTime <= currentTime;
      const continuationCallback = callback(didUserCallbackTimeout);
      currentTime = getCurrentTime();
      if (typeof continuationCallback === "function") {
        currentTask.callback = continuationCallback;
        return true;
      }
      if (currentTask === peek(taskQueue)) {
        pop(taskQueue);
      }
    } else {
      pop(taskQueue);
    }
    currentTask = peek(taskQueue);
  }
  if (currentTask !== null) {
    return true;
  }
  return false;
}

export {
  NormalPriority as unstable_NormalPriority,
  unstable_scheduleCallback,
+ shouldYieldToHost as unstable_shouldYield
};

38.5 ReactFiberLane.js #

src\react-reconciler\src\ReactFiberLane.js

+import { allowConcurrentByDefault } from 'shared/ReactFeatureFlags';

export const TotalLanes = 31;
export const NoLanes = 0b0000000000000000000000000000000;
export const NoLane = 0b0000000000000000000000000000000;
export const SyncLane = 0b0000000000000000000000000000001;// 1
export const InputContinuousLane = 0b0000000000000000000000000000100;// 4
export const DefaultLane = 0b0000000000000000000000000010000;// 16
export const NonIdleLanes = 0b0001111111111111111111111111111;
export const IdleLane = 0b0100000000000000000000000000000;

export function mergeLanes(a, b) {
  return a | b;
}
export function markRootUpdated(root, updateLane) {
  root.pendingLanes |= updateLane;
}

export function getNextLanes(root) {
  const pendingLanes = root.pendingLanes;
  if (pendingLanes === NoLanes) {
    return NoLanes;
  }
  const nextLanes = getHighestPriorityLanes(pendingLanes);
  return nextLanes;
}

function getHighestPriorityLanes(lanes) {
  return getHighestPriorityLane(lanes);
}

export function getHighestPriorityLane(lanes) {
  return lanes & -lanes;
}

export function includesNonIdleWork(lanes) {
  return (lanes & NonIdleLanes) !== NoLanes;
}
export function includesBlockingLane(root, lanes) {
+ if (allowConcurrentByDefault) {
+   return false;
+ }
  const SyncDefaultLanes = InputContinuousLane | DefaultLane;
  return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function isSubsetOfLanes(set, subset) {
  return (set & subset) === subset;
}

38.6 ReactFeatureFlags.js #

src\shared\ReactFeatureFlags.js

export const allowConcurrentByDefault = true;

39.批量更新 #

39.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

+function FunctionComponent() {
+  console.log('FunctionComponent');
+  const [number, setNumber] = React.useState(0);
+  React.useEffect(() => {
+    setNumber(number => number + 1)
+    setNumber(number => number + 1)
+  }, []);
+  return (<button onClick={() => {
+    setNumber(number => number + 1)
+    setNumber(number => number + 1)
+  }}>{number}</button>)
+}
const element = <FunctionComponent />;
const container = document.getElementById("root");
const root = createRoot(container, { unstable_concurrentUpdatesByDefault: true });
root.render(element);

39.2 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber, requestUpdateLane } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";
+import { NoLanes } from './ReactFiberLane';

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
  useLayoutEffect: mountLayoutEffect,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
  useLayoutEffect: updateLayoutEffect,
};
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
function updateLayoutEffect(create, deps) {
  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
}
function mountLayoutEffect(create, deps) {
  const fiberFlags = UpdateEffect;
  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
}
function updateEffect(create, deps) {
  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  const pendingQueue = queue.pending;
  let baseQueue = null;
  let newState = current.memoizedState;
  if (pendingQueue !== null) {
    baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    const first = baseQueue.next;
    let update = first;
    do {
      if (update.hasEagerState) {
        newState = update.eagerState;
      } else {
        const action = update.action;
        newState = reducer(newState, action);
      }
      update = update.next;
    } while (update !== null && update !== first);
  }
  hook.memoizedState = newState;
  queue.lastRenderedState = newState;
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const lane = requestUpdateLane(fiber);
  const update = {
    lane,
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
+ const alternate = fiber.alternate;
+ if (fiber.lanes === NoLanes && (alternate === null || alternate.lanes === NoLanes)) {
    const lastRenderedReducer = queue.lastRenderedReducer;
    const currentState = queue.lastRenderedState;
    const eagerState = lastRenderedReducer(currentState, action);
    update.hasEagerState = true;
    update.eagerState = eagerState;
    if (is(eagerState, currentState)) {
      return;
    }
+ }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update, lane);
  scheduleUpdateOnFiber(root, fiber, lane);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
  workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

39.3 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import {
  scheduleCallback as Scheduler_scheduleCallback,
  ImmediatePriority as ImmediateSchedulerPriority,
  UserBlockingPriority as UserBlockingSchedulerPriority,
  NormalPriority as NormalSchedulerPriority,
  IdlePriority as IdleSchedulerPriority,
  shouldYield
} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import {
  NoLane, markRootUpdated, NoLanes,
  getNextLanes, getHighestPriorityLane, SyncLane,
  includesBlockingLane
} from './ReactFiberLane';
import {
  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
  DefaultEventPriority, IdleEventPriority, setCurrentUpdatePriority
} from './ReactEventPriorities';
import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';
import { scheduleSyncCallback, flushSyncCallbacks } from './ReactFiberSyncTaskQueue';

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
let workInProgressRootRenderLanes = NoLanes;

const RootInProgress = 0;
const RootCompleted = 5;
let workInProgressRoot = null;
let workInProgressRootExitStatus = RootInProgress;

export function scheduleUpdateOnFiber(root, fiber, lane) {
  markRootUpdated(root, lane);
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
  const nextLanes = getNextLanes(root, NoLanes);
  if (nextLanes === NoLanes) {
    root.callbackNode = null;
    root.callbackPriority = NoLane;
    return;
  }
  const newCallbackPriority = getHighestPriorityLane(nextLanes);
+ const existingCallbackPriority = root.callbackPriority;
+ if (existingCallbackPriority === newCallbackPriority) {
+   return;
+ }
+  let newCallbackNode;
  if (newCallbackPriority === SyncLane) {
    scheduleSyncCallback(performSyncWorkOnRoot.bind(null, root));
    queueMicrotask(flushSyncCallbacks);
    newCallbackNode = null;
  } else {
    let schedulerPriorityLevel;
    switch (lanesToEventPriority(nextLanes)) {
      case DiscreteEventPriority:
        schedulerPriorityLevel = ImmediateSchedulerPriority;
        break;
      case ContinuousEventPriority:
        schedulerPriorityLevel = UserBlockingSchedulerPriority;
        break;
      case DefaultEventPriority:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
      case IdleEventPriority:
        schedulerPriorityLevel = IdleSchedulerPriority;
        break;
      default:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
    }
+   newCallbackNode = Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
+ root.callbackPriority = newCallbackPriority;
+ root.callbackNode = newCallbackNode;
}
function performSyncWorkOnRoot(root) {
  const lanes = getNextLanes(root, NoLanes);
  renderRootSync(root, lanes);
  const finishedWork = root.current.alternate
  root.finishedWork = finishedWork
  commitRoot(root)
  return null;
}
function performConcurrentWorkOnRoot(root, didTimeout) {
  const originalCallbackNode = root.callbackNode;
  const lanes = getNextLanes(root, NoLanes);
  if (lanes === NoLanes) {
    return null;
  }
  const shouldTimeSlice = !includesBlockingLane(root, lanes) && (!didTimeout);
  const exitStatus = shouldTimeSlice ? renderRootConcurrent(root, lanes) : renderRootSync(root, lanes);
  if (exitStatus !== RootInProgress) {
    const finishedWork = root.current.alternate
    root.finishedWork = finishedWork
    commitRoot(root)
  }
  if (root.callbackNode === originalCallbackNode) {
    return performConcurrentWorkOnRoot.bind(null, root);
  }
  return null;
}
function renderRootConcurrent(root, lanes) {
  if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes);
  }
  workLoopConcurrent();
  if (workInProgress !== null) {
    return RootInProgress;
  }
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}
function workLoopConcurrent() {
  while (workInProgress !== null && !shouldYield()) {
    performUnitOfWork(workInProgress);
  }
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const previousPriority = getCurrentUpdatePriority();
  try {
    setCurrentUpdatePriority(DiscreteEventPriority);
    commitRootImpl(root);
  } finally {
    setCurrentUpdatePriority(previousPriority);
  }
}
function commitRootImpl(root) {
  const { finishedWork } = root;
  root.callbackNode = null;
+ root.callbackPriority = NoLane;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root, lanes) {
  workInProgress = createWorkInProgress(root.current, null);
  workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root, lanes) {
  if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes)
  }
  workLoopSync();
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
  if (workInProgressRootExitStatus === RootInProgress) {
    workInProgressRootExitStatus = RootCompleted;
  }
}

export function requestUpdateLane() {
  const updateLane = getCurrentUpdatePriority();
  if (updateLane !== NoLane) {
    return updateLane;
  }
  const eventLane = getCurrentEventPriority();
  return eventLane;
}

40.高优更新打断低优更新(useRef) #

40.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

function FunctionComponent() {
+function FunctionComponent() {
+  const [numbers, setNumbers] = React.useState(new Array(10).fill('A'));
+  const divRef = React.useRef();
+  React.useEffect(() => {
+    setTimeout(() => {
+      divRef.current.click();
+    }, 10);
+    setNumbers(numbers => numbers.map(item => item + 'B'))
+  }, []);
+  return (<div ref={divRef} onClick={() => {
+    setNumbers(numbers => numbers.map(item => item + 'C'))
+  }}>{numbers.map((number, index) => <span key={index}>{number}</span>)}</div>)
+}
const element = <FunctionComponent />;
const container = document.getElementById("root");
const root = createRoot(container, { unstable_concurrentUpdatesByDefault: true });
root.render(element);

40.2 react\index.js #

src\react\index.js

export {
  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
  useReducer,
  useState,
  useEffect,
  useLayoutEffect,
+ useRef
} from "./src/React";

40.3 React.js #

src\react\src\React.js

+import { useReducer, useState, useEffect, useLayoutEffect, useRef } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";

export {
  useReducer,
  useState,
  useEffect,
  useLayoutEffect,
+ useRef,
  ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
};

40.4 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

export function useState(initialState) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

export function useEffect(create, deps) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useEffect(create, deps);
}
export function useLayoutEffect(create, deps) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useLayoutEffect(create, deps);
}
+export function useRef(initialValue) {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useRef(initialValue);
+}

40.5 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import {
  scheduleCallback as Scheduler_scheduleCallback,
  ImmediatePriority as ImmediateSchedulerPriority,
  UserBlockingPriority as UserBlockingSchedulerPriority,
  NormalPriority as NormalSchedulerPriority,
  IdlePriority as IdleSchedulerPriority,
  shouldYield，
+ cancelCallback as Scheduler_cancelCallback
} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import {
  NoLane, markRootUpdated, NoLanes,
  getNextLanes, getHighestPriorityLane, SyncLane,
  includesBlockingLane
} from './ReactFiberLane';
import {
  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
  DefaultEventPriority, IdleEventPriority, setCurrentUpdatePriority
} from './ReactEventPriorities';
import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';
import { scheduleSyncCallback, flushSyncCallbacks } from './ReactFiberSyncTaskQueue';

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
let workInProgressRootRenderLanes = NoLanes;

const RootInProgress = 0;
const RootCompleted = 5;
let workInProgressRoot = null;
let workInProgressRootExitStatus = RootInProgress;

export function scheduleUpdateOnFiber(root, fiber, lane) {
  markRootUpdated(root, lane);
  ensureRootIsScheduled(root);
}
function ensureRootIsScheduled(root) {
+ const existingCallbackNode = root.callbackNode;
+ const nextLanes = getNextLanes(root, root === workInProgressRoot ? workInProgressRootRenderLanes : NoLanes);
  if (nextLanes === NoLanes) {
    root.callbackNode = null;
    root.callbackPriority = NoLane;
    return;
  }
  const newCallbackPriority = getHighestPriorityLane(nextLanes);
  const existingCallbackPriority = root.callbackPriority;
  if (existingCallbackPriority === newCallbackPriority) {
    return;
  }
+ if (existingCallbackNode != null) {
+   Scheduler_cancelCallback(existingCallbackNode);
+ }
  let newCallbackNode;
  if (newCallbackPriority === SyncLane) {
    scheduleSyncCallback(performSyncWorkOnRoot.bind(null, root));
    queueMicrotask(flushSyncCallbacks);
    newCallbackNode = null;
  } else {
    let schedulerPriorityLevel;
    switch (lanesToEventPriority(nextLanes)) {
      case DiscreteEventPriority:
        schedulerPriorityLevel = ImmediateSchedulerPriority;
        break;
      case ContinuousEventPriority:
        schedulerPriorityLevel = UserBlockingSchedulerPriority;
        break;
      case DefaultEventPriority:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
      case IdleEventPriority:
        schedulerPriorityLevel = IdleSchedulerPriority;
        break;
      default:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
    }
    newCallbackNode = Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
  root.callbackPriority = newCallbackPriority;
  root.callbackNode = newCallbackNode;
}
function performSyncWorkOnRoot(root) {
  const lanes = getNextLanes(root, NoLanes);
  renderRootSync(root, lanes);
  const finishedWork = root.current.alternate
  root.finishedWork = finishedWork
  commitRoot(root)
  return null;
}
function performConcurrentWorkOnRoot(root, didTimeout) {
  const originalCallbackNode = root.callbackNode;
  const lanes = getNextLanes(root, NoLanes);
  if (lanes === NoLanes) {
    return null;
  }
  const shouldTimeSlice = !includesBlockingLane(root, lanes) && (!didTimeout);
  const exitStatus = shouldTimeSlice ? renderRootConcurrent(root, lanes) : renderRootSync(root, lanes);
  if (exitStatus !== RootInProgress) {
    const finishedWork = root.current.alternate
    root.finishedWork = finishedWork
    commitRoot(root)
  }
  if (root.callbackNode === originalCallbackNode) {
    return performConcurrentWorkOnRoot.bind(null, root);
  }
  return null;
}
function renderRootConcurrent(root, lanes) {
  if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes);
  }
  workLoopConcurrent();
  if (workInProgress !== null) {
    return RootInProgress;
  }
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}
function workLoopConcurrent() {
  while (workInProgress !== null && !shouldYield()) {
    performUnitOfWork(workInProgress);
  }
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const previousPriority = getCurrentUpdatePriority();
  try {
    setCurrentUpdatePriority(DiscreteEventPriority);
    commitRootImpl(root);
  } finally {
    setCurrentUpdatePriority(previousPriority);
  }
}
function commitRootImpl(root) {
  const { finishedWork } = root;
  console.log('commit', finishedWork.child.memoizedState.memoizedState);
  root.callbackNode = null;
  root.callbackPriority = NoLane;
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
}
function prepareFreshStack(root, lanes) {
  workInProgress = createWorkInProgress(root.current, null);
  workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root, lanes) {
  if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes)
  }
  workLoopSync();
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
  if (workInProgressRootExitStatus === RootInProgress) {
    workInProgressRootExitStatus = RootCompleted;
  }
}

export function requestUpdateLane() {
  const updateLane = getCurrentUpdatePriority();
  if (updateLane !== NoLane) {
    return updateLane;
  }
  const eventLane = getCurrentEventPriority();
  return eventLane;
}

40.6 ReactFiberLane.js #

src\react-reconciler\src\ReactFiberLane.js

import { allowConcurrentByDefault } from 'shared/ReactFeatureFlags';

export const TotalLanes = 31;
export const NoLanes = 0b0000000000000000000000000000000;
export const NoLane = 0b0000000000000000000000000000000;
export const SyncLane = 0b0000000000000000000000000000001;// 1
export const InputContinuousLane = 0b0000000000000000000000000000100;// 4
export const DefaultLane = 0b0000000000000000000000000010000;// 16
export const NonIdleLanes = 0b0001111111111111111111111111111;
export const IdleLane = 0b0100000000000000000000000000000;

export function mergeLanes(a, b) {
  return a | b;
}
export function markRootUpdated(root, updateLane) {
  root.pendingLanes |= updateLane;
}

+export function getNextLanes(root, wipLanes) {
  const pendingLanes = root.pendingLanes;
  if (pendingLanes === NoLanes) {
    return NoLanes;
  }
  const nextLanes = getHighestPriorityLanes(pendingLanes);
+ if (wipLanes !== NoLanes && wipLanes !== nextLanes) {
+   if (nextLanes >= wipLanes) {
+     return wipLanes;
+   }
+ }
  return nextLanes;
}

function getHighestPriorityLanes(lanes) {
  return getHighestPriorityLane(lanes);
}

export function getHighestPriorityLane(lanes) {
  return lanes & -lanes;
}

export function includesNonIdleWork(lanes) {
  return (lanes & NonIdleLanes) !== NoLanes;
}
export function includesBlockingLane(root, lanes) {
  if (allowConcurrentByDefault) {
    return false;
  }
  const SyncDefaultLanes = InputContinuousLane | DefaultLane;
  return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function isSubsetOfLanes(set, subset) {
  return (set & subset) === subset;
}

40.7 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber, requestUpdateLane } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";
import { NoLanes } from './ReactFiberLane';

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
  useLayoutEffect: mountLayoutEffect,
+ useRef: mountRef,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
  useLayoutEffect: updateLayoutEffect,
+ useRef: updateRef
};
+function mountRef(initialValue) {
+  const hook = mountWorkInProgressHook();
+  const ref = {
+    current: initialValue,
+  };
+  hook.memoizedState = ref;
+  return ref;
+}
+function updateRef() {
+  const hook = updateWorkInProgressHook();
+  return hook.memoizedState;
+}
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
function updateLayoutEffect(create, deps) {
  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
}
function mountLayoutEffect(create, deps) {
  const fiberFlags = UpdateEffect;
  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
}
function updateEffect(create, deps) {
  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  const pendingQueue = queue.pending;
  let baseQueue = null;
  let newState = current.memoizedState;
  if (pendingQueue !== null) {
    baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    const first = baseQueue.next;
    let update = first;
    do {
      if (update.hasEagerState) {
        newState = update.eagerState;
      } else {
        const action = update.action;
        newState = reducer(newState, action);
      }
      update = update.next;
    } while (update !== null && update !== first);
  }
  hook.memoizedState = newState;
  queue.lastRenderedState = newState;
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const lane = requestUpdateLane(fiber);
  const update = {
    lane,
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const alternate = fiber.alternate;
  if (fiber.lanes === NoLanes && (alternate === null || alternate.lanes === NoLanes)) {
    const lastRenderedReducer = queue.lastRenderedReducer;
    const currentState = queue.lastRenderedState;
    const eagerState = lastRenderedReducer(currentState, action);
    update.hasEagerState = true;
    update.eagerState = eagerState;
    if (is(eagerState, currentState)) {
      return;
    }
  }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update, lane);
  scheduleUpdateOnFiber(root, fiber, lane);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props) {
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
  workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  return children;
}

40.8 ReactFiberFlags.js #

src\react-reconciler\src\ReactFiberFlags.js

export const NoFlags = 0b00000000000000000000000000;
export const Placement = 0b00000000000000000000000010;
export const Update = 0b00000000000000000000000100;
export const ChildDeletion = 0b00000000000000000000001000;
export const Passive = 0b00000000000000010000000000;
export const LayoutMask = Update;
+export const Ref = 0b00000000000000000100000000;
+export const MutationMask = Placement | Update | Ref;

40.9 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
  prepareUpdate,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HostComponent, HostRoot, HostText, FunctionComponent } from "./ReactWorkTags";
+import { Ref, NoFlags, Update } from "./ReactFiberFlags";
+
+function markRef(workInProgress) {
+  workInProgress.flags |= Ref;
+}

function bubbleProperties(completedWork) {
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}
function markUpdate(workInProgress) {
  workInProgress.flags |= Update;
}
function updateHostComponent(current, workInProgress, type, newProps) {
  const oldProps = current.memoizedProps;
  const instance = workInProgress.stateNode;
  const updatePayload = prepareUpdate(instance, type, oldProps, newProps);
  workInProgress.updateQueue = updatePayload;
  if (updatePayload) {
    markUpdate(workInProgress);
  }
}
export function completeWork(current, workInProgress) {
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
      if (current !== null && workInProgress.stateNode != null) {
        updateHostComponent(current, workInProgress, type, newProps);
+       if (current.ref !== workInProgress.ref) {
+         markRef(workInProgress);
+       }
      } else {
        const instance = createInstance(type, newProps, workInProgress);
        appendAllChildren(instance, workInProgress);
        workInProgress.stateNode = instance;
        finalizeInitialChildren(instance, type, newProps);
+       if (workInProgress.ref !== null) {
+         markRef(workInProgress);
+       }
      }
      bubbleProperties(workInProgress);
      return null;
      break;
    }
    case FunctionComponent:
      bubbleProperties(workInProgress);
      break;
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
    default:
      break;
  }
}

40.10 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

import { HostRoot, HostComponent, HostText, FunctionComponent } from "./ReactWorkTags";
+import { Passive, MutationMask, Placement, Update, LayoutMask, Ref } from "./ReactFiberFlags";
import { insertBefore, appendChild, commitUpdate, removeChild } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";

export function commitMutationEffects(finishedWork, root) {
  commitMutationEffectsOnFiber(finishedWork, root);
}
export function commitPassiveUnmountEffects(finishedWork) {
  commitPassiveUnmountOnFiber(finishedWork);
}
function commitPassiveUnmountOnFiber(finishedWork) {
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      if (finishedWork.flags & Passive) {
        commitHookPassiveUnmountEffects(finishedWork, finishedWork.return, HookPassive | HookHasEffect);
      }
      break;
    }
    default: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      break;
    }
  }
}
function recursivelyTraversePassiveUnmountEffects(parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveUnmountOnFiber(child);
      child = child.sibling;
    }
  }
}
function commitHookPassiveUnmountEffects(finishedWork, nearestMountedAncestor, hookFlags) {
  commitHookEffectListUnmount(hookFlags, finishedWork, nearestMountedAncestor);
}

function commitHookEffectListUnmount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const destroy = effect.destroy;
        effect.destroy = undefined;
        if (destroy !== undefined) {
          destroy();
        }
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}

export function commitPassiveMountEffects(root, finishedWork) {
  commitPassiveMountOnFiber(root, finishedWork);
}
function commitPassiveMountOnFiber(finishedRoot, finishedWork) {
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      if (flags & Passive) {
        commitHookPassiveMountEffects(finishedWork, HookPassive | HookHasEffect);
      }
      break;
    }
    case HostRoot: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      break;
    }
    default:
      break;
  }
}
function commitHookPassiveMountEffects(finishedWork, hookFlags) {
  commitHookEffectListMount(hookFlags, finishedWork);
}
function commitHookEffectListMount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const create = effect.create;
        effect.destroy = create();
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}
function recursivelyTraversePassiveMountEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveMountOnFiber(root, child);
      child = child.sibling;
    }
  }
}
let hostParent = null;
function commitDeletionEffects(root, returnFiber, deletedFiber) {
  let parent = returnFiber;
  findParent: while (parent !== null) {
    switch (parent.tag) {
      case HostComponent: {
        hostParent = parent.stateNode;
        break findParent;
      }
      case HostRoot: {
        hostParent = parent.stateNode.containerInfo;
        break findParent;
      }
      default:
        break;
    }
    parent = parent.return;
  }
  commitDeletionEffectsOnFiber(root, returnFiber, deletedFiber);
  hostParent = null;
}
function commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, deletedFiber) {
  switch (deletedFiber.tag) {
    case HostComponent:
    case HostText: {
      recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, deletedFiber);
      if (hostParent !== null) {
        removeChild(hostParent, deletedFiber.stateNode);
      }
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, parent) {
  let child = parent.child;
  while (child !== null) {
    commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, child);
    child = child.sibling;
  }
}
function recursivelyTraverseMutationEffects(root, parentFiber) {
  const deletions = parentFiber.deletions;
  if (deletions !== null) {
    for (let i = 0; i < deletions.length; i++) {
      const childToDelete = deletions[i];
      commitDeletionEffects(root, parentFiber, childToDelete);
    }
  }
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  const current = finishedWork.alternate;
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case HostRoot: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case FunctionComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Update) {
        commitHookEffectListUnmount(HookLayout | HookHasEffect, finishedWork, finishedWork.return);
      }
      break;
    }
    case HostComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
+     if (flags & Ref) {
+       commitAttachRef(finishedWork);
+     }
      if (flags & Update) {
        const instance = finishedWork.stateNode;
        if (instance != null) {
          const newProps = finishedWork.memoizedProps;
          const oldProps = current !== null ? current.memoizedProps : newProps;
          const type = finishedWork.type;
          const updatePayload = finishedWork.updateQueue;
          finishedWork.updateQueue = null;
          if (updatePayload !== null) {
            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
          }
        }
      }

      break;
    }
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    default: {
      break;
    }
  }
}
+function commitAttachRef(finishedWork) {
+  const ref = finishedWork.ref;
+  if (ref !== null) {
+    const instance = finishedWork.stateNode;
+    if (typeof ref === "function") {
+      ref(instance)
+    } else {
+      ref.current = instance;
+    }
+  }
+}
export function commitLayoutEffects(finishedWork, root) {
  const current = finishedWork.alternate;
  commitLayoutEffectOnFiber(root, current, finishedWork);
}
function commitLayoutEffectOnFiber(finishedRoot, current, finishedWork) {
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
      if (flags & Update) {
        commitHookLayoutEffects(finishedWork, HookLayout | HookHasEffect);
      }
      break;
    }
    case HostRoot: {
      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseLayoutEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & LayoutMask) {
    let child = parentFiber.child;
    while (child !== null) {
      const current = child.alternate;
      commitLayoutEffectOnFiber(root, current, child);
      child = child.sibling;
    }
  }
}
function commitHookLayoutEffects(finishedWork, hookFlags) {
  commitHookEffectListMount(hookFlags, finishedWork);
}

40.11 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

import { HostRoot, IndeterminateComponent, HostComponent, HostText } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.deletions = null;
  this.alternate = null;

  this.index = 0;
+ this.ref = null;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}
// We use a double buffering pooling technique because we know that we'll
// only ever need at most two versions of a tree. We pool the "other" unused
// node that we're free to reuse. This is lazily created to avoid allocating
// extra objects for things that are never updated. It also allow us to
// reclaim the extra memory if needed.
//我们使用双缓冲池技术，因为我们知道一棵树最多只需要两个版本
//我们将“其他”未使用的我们可以自由重用的节点
//这是延迟创建的，以避免分配从未更新的内容的额外对象。它还允许我们如果需要，回收额外的内存
export function createWorkInProgress(current, pendingProps) {
  let workInProgress = current.alternate;
  if (workInProgress === null) {
    workInProgress = createFiber(current.tag, pendingProps, current.key);
    workInProgress.type = current.type;
    workInProgress.stateNode = current.stateNode;
    workInProgress.alternate = current;
    current.alternate = workInProgress;
  } else {
    workInProgress.pendingProps = pendingProps;
    workInProgress.type = current.type;
    workInProgress.flags = NoFlags;
    workInProgress.subtreeFlags = NoFlags;
  }
  workInProgress.child = current.child;
  workInProgress.memoizedProps = current.memoizedProps;
  workInProgress.memoizedState = current.memoizedState;
  workInProgress.updateQueue = current.updateQueue;
  workInProgress.sibling = current.sibling;
  workInProgress.index = current.index;
+ workInProgress.ref = current.ref;
  return workInProgress;
}
export function createFiberFromTypeAndProps(type, key, pendingProps) {
  let fiberTag = IndeterminateComponent;
  if (typeof type === "string") {
    fiberTag = HostComponent;
  }
  const fiber = createFiber(fiberTag, pendingProps, key);
  fiber.type = type;
  return fiber;
}
export function createFiberFromElement(element) {
  const { type } = element;
  const { key } = element;
  const pendingProps = element.props;
  const fiber = createFiberFromTypeAndProps(type, key, pendingProps);
  return fiber;
}

export function createFiberFromText(content) {
  const fiber = createFiber(HostText, content, null);
  return fiber;
}

40.12 ReactChildFiber.js #

src\react-reconciler\src\ReactChildFiber.js

import { REACT_ELEMENT_TYPE } from "shared/ReactSymbols";
import isArray from "shared/isArray";
import { createFiberFromElement, FiberNode, createFiberFromText, createWorkInProgress } from "./ReactFiber";
import { Placement, ChildDeletion } from "./ReactFiberFlags";
import { HostText } from "./ReactWorkTags";
function createChildReconciler(shouldTrackSideEffects) {
  function useFiber(fiber, pendingProps) {
    const clone = createWorkInProgress(fiber, pendingProps);
    clone.index = 0;
    clone.sibling = null;
    return clone;
  }
  function deleteChild(returnFiber, childToDelete) {
    if (!shouldTrackSideEffects) {
      return;
    }
    const deletions = returnFiber.deletions;
    if (deletions === null) {
      returnFiber.deletions = [childToDelete];
      returnFiber.flags |= ChildDeletion;
    } else {
      deletions.push(childToDelete);
    }
  }
  function deleteRemainingChildren(returnFiber, currentFirstChild) {
    if (!shouldTrackSideEffects) {
      return null;
    }
    let childToDelete = currentFirstChild;
    while (childToDelete !== null) {
      deleteChild(returnFiber, childToDelete);
      childToDelete = childToDelete.sibling;
    }
    return null;
  }
  function reconcileSingleElement(returnFiber, currentFirstChild, element) {
    const key = element.key;
    let child = currentFirstChild;
    while (child !== null) {
      if (child.key === key) {
        const elementType = element.type;
        if (child.type === elementType) {
          deleteRemainingChildren(returnFiber, child.sibling);
          const existing = useFiber(child, element.props);
+         existing.ref = element.ref;
          existing.return = returnFiber;
          return existing;
        }
        deleteRemainingChildren(returnFiber, child);
        break;
      } else {
        deleteChild(returnFiber, child);
      }
      child = child.sibling;
    }
    const created = createFiberFromElement(element);
+   created.ref = element.ref;
    created.return = returnFiber;
    return created;
  }
  function placeSingleChild(newFiber) {
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.flags |= Placement;
    }
    return newFiber;
  }
  function reconcileSingleTextNode(returnFiber, currentFirstChild, content) {
    const created = new FiberNode(HostText, { content }, null);
    created.return = returnFiber;
    return created;
  }
  function createChild(returnFiber, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const created = createFiberFromText(`${newChild}`);
      created.return = returnFiber;
      return created;
    }

    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const created = createFiberFromElement(newChild);
+         created.ref = newChild.ref;
          created.return = returnFiber;
          return created;
        }
        default:
          break;
      }
    }
    return null;
  }
  function placeChild(newFiber, lastPlacedIndex, newIndex) {
    newFiber.index = newIndex;
    if (!shouldTrackSideEffects) {
      return lastPlacedIndex;
    }
    const current = newFiber.alternate;
    if (current !== null) {
      const oldIndex = current.index;
      if (oldIndex < lastPlacedIndex) {
        newFiber.flags |= Placement;
        return lastPlacedIndex;
      } else {
        return oldIndex;
      }
    } else {
      newFiber.flags |= Placement;
      return lastPlacedIndex;
    }
  }
  function updateElement(returnFiber, current, element) {
    const elementType = element.type;
    if (current !== null) {
      if (current.type === elementType) {
        const existing = useFiber(current, element.props);
+       existing.ref = element.ref;
        existing.return = returnFiber;
        return existing;
      }
    }
    const created = createFiberFromElement(element);
+   created.ref = element.ref;
    created.return = returnFiber;
    return created;
  }
  function updateSlot(returnFiber, oldFiber, newChild) {
    const key = oldFiber !== null ? oldFiber.key : null;
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          if (newChild.key === key) {
            return updateElement(returnFiber, oldFiber, newChild);
          } else {
            return null;
          }
        }
        default:
          return null;
      }
    }
  }
  function mapRemainingChildren(returnFiber, currentFirstChild) {
    const existingChildren = new Map();
    let existingChild = currentFirstChild;
    while (existingChild !== null) {
      if (existingChild.key !== null) {
        existingChildren.set(existingChild.key, existingChild);
      } else {
        existingChildren.set(existingChild.index, existingChild);
      }
      existingChild = existingChild.sibling;
    }
    return existingChildren;
  }
  function updateTextNode(returnFiber, current, textContent) {
    if (current === null || current.tag !== HostText) {
      const created = createFiberFromText(textContent, returnFiber.mode);
      created.return = returnFiber;
      return created;
    } else {
      const existing = useFiber(current, textContent);
      existing.return = returnFiber;
      return existing;
    }
  }
  function updateFromMap(existingChildren, returnFiber, newIdx, newChild) {
    if ((typeof newChild === "string" && newChild !== "") || typeof newChild === "number") {
      const matchedFiber = existingChildren.get(newIdx) || null;
      return updateTextNode(returnFiber, matchedFiber, "" + newChild);
    }
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          const matchedFiber = existingChildren.get(newChild.key === null ? newIdx : newChild.key) || null;
          return updateElement(returnFiber, matchedFiber, newChild);
        }
      }
    }
    return null;
  }
  function reconcileChildrenArray(returnFiber, currentFirstChild, newChildren) {
    let resultingFirstChild = null;
    let previousNewFiber = null;
    let newIdx = 0;
    let oldFiber = currentFirstChild;
    let nextOldFiber = null;
    let lastPlacedIndex = 0;
    for (; oldFiber !== null && newIdx < newChildren.length; newIdx++) {
      nextOldFiber = oldFiber.sibling;
      const newFiber = updateSlot(returnFiber, oldFiber, newChildren[newIdx]);
      if (newFiber === null) {
        break;
      }
      if (shouldTrackSideEffects) {
        if (oldFiber && newFiber.alternate === null) {
          deleteChild(returnFiber, oldFiber);
        }
      }
      lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
      if (previousNewFiber === null) {
        resultingFirstChild = newFiber;
      } else {
        previousNewFiber.sibling = newFiber;
      }
      previousNewFiber = newFiber;
      oldFiber = nextOldFiber;
    }
    if (newIdx === newChildren.length) {
      deleteRemainingChildren(returnFiber, oldFiber);
      return resultingFirstChild;
    }
    if (oldFiber === null) {
      for (; newIdx < newChildren.length; newIdx++) {
        const newFiber = createChild(returnFiber, newChildren[newIdx]);
        if (newFiber === null) {
          continue;
        }
        lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
        if (previousNewFiber === null) {
          resultingFirstChild = newFiber;
        } else {
          previousNewFiber.sibling = newFiber;
        }
        previousNewFiber = newFiber;
      }
    }
    const existingChildren = mapRemainingChildren(returnFiber, oldFiber);
    for (; newIdx < newChildren.length; newIdx++) {
      const newFiber = updateFromMap(existingChildren, returnFiber, newIdx, newChildren[newIdx]);
      if (newFiber !== null) {
        if (shouldTrackSideEffects) {
          if (newFiber.alternate !== null) {
            existingChildren.delete(newFiber.key === null ? newIdx : newFiber.key);
          }
        }
        lastPlacedIndex = placeChild(newFiber, lastPlacedIndex, newIdx);
        if (previousNewFiber === null) {
          resultingFirstChild = newFiber;
        } else {
          previousNewFiber.sibling = newFiber;
        }
        previousNewFiber = newFiber;
      }
    }
    if (shouldTrackSideEffects) {
      existingChildren.forEach((child) => deleteChild(returnFiber, child));
    }
    return resultingFirstChild;
  }
  function reconcileChildFibers(returnFiber, currentFirstChild, newChild) {
    if (typeof newChild === "object" && newChild !== null) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE: {
          return placeSingleChild(reconcileSingleElement(returnFiber, currentFirstChild, newChild));
        }
        default:
          break;
      }
      if (isArray(newChild)) {
        return reconcileChildrenArray(returnFiber, currentFirstChild, newChild);
      }
    }
    if (typeof newChild === "string") {
      return placeSingleChild(reconcileSingleTextNode(returnFiber, currentFirstChild, newChild));
    }
    return null;
  }
  return reconcileChildFibers;
}
export const reconcileChildFibers = createChildReconciler(true);
export const mountChildFibers = createChildReconciler(false);

41.饥饿问题 #

41.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

+let counter = 0;
+let timer;
+let bCounter = 0;
+let cCounter = 0;
+function FunctionComponent() {
+  const [numbers, setNumbers] = React.useState(new Array(100).fill('A'));
+  const divRef = React.useRef();
+  const updateB = (numbers) => new Array(100).fill(numbers[0] + 'B')
+  updateB.id = 'updateB' + (bCounter++);
+  const updateC = (numbers) => new Array(100).fill(numbers[0] + 'C')
+  updateC.id = 'updateC' + (cCounter++);
+  React.useEffect(() => {
+    timer = setInterval(() => {
+      console.log(divRef);
+      divRef.current.click();
+      if (counter++ === 0) {
+        setNumbers(updateB)
+      }
+      divRef.current.click();
+      if (counter++ > 10) {
+        clearInterval(timer);
+      }
+    });
+  }, []);
+  return (<div ref={divRef} onClick={() => setNumbers(updateC)}>
+    {numbers.map((number, index) => <span key={index}>{number}</span>)}</ div>)
+}

const element = <FunctionComponent />;
const container = document.getElementById("root");
const root = createRoot(container, { unstable_concurrentUpdatesByDefault: true });
root.render(element);

41.2 Scheduler.js #

src\scheduler\src\forks\Scheduler.js

import {
  ImmediatePriority,
  UserBlockingPriority,
  NormalPriority,
  LowPriority,
  IdlePriority,
} from "../SchedulerPriorities";
import { push, pop, peek } from "../SchedulerMinHeap";
import { frameYieldMs } from "../SchedulerFeatureFlags";

const maxSigned31BitInt = 1073741823;
const IMMEDIATE_PRIORITY_TIMEOUT = -1;
const USER_BLOCKING_PRIORITY_TIMEOUT = 250;
const NORMAL_PRIORITY_TIMEOUT = 5000;
const LOW_PRIORITY_TIMEOUT = 10000;
const IDLE_PRIORITY_TIMEOUT = maxSigned31BitInt;

const taskQueue = [];
let taskIdCounter = 1;
let scheduledHostCallback = null;
let startTime = -1;
let currentTask = null;
const frameInterval = frameYieldMs;
const channel = new MessageChannel();
const port = channel.port2;

const getCurrentTime = () => performance.now();
channel.port1.onmessage = performWorkUntilDeadline;

function schedulePerformWorkUntilDeadline() {
  port.postMessage(null);
}
function performWorkUntilDeadline() {
  if (scheduledHostCallback !== null) {
    startTime = getCurrentTime();
    let hasMoreWork = true;
    try {
      hasMoreWork = scheduledHostCallback(startTime);
    } finally {
      if (hasMoreWork) {
        schedulePerformWorkUntilDeadline();
      } else {
        scheduledHostCallback = null;
      }
    }
  }
}
function requestHostCallback(callback) {
  scheduledHostCallback = callback;
  schedulePerformWorkUntilDeadline();
}

function unstable_scheduleCallback(priorityLevel, callback) {
  const currentTime = getCurrentTime();
  const startTime = currentTime;
  let timeout;
  switch (priorityLevel) {
    case ImmediatePriority:
      timeout = IMMEDIATE_PRIORITY_TIMEOUT;
      break;
    case UserBlockingPriority:
      timeout = USER_BLOCKING_PRIORITY_TIMEOUT;
      break;
    case IdlePriority:
      timeout = IDLE_PRIORITY_TIMEOUT;
      break;
    case LowPriority:
      timeout = LOW_PRIORITY_TIMEOUT;
      break;
    case NormalPriority:
    default:
      timeout = NORMAL_PRIORITY_TIMEOUT;
      break;
  }
  const expirationTime = startTime + timeout;
  const newTask = {
    id: taskIdCounter++,
    callback,
    priorityLevel,
    startTime,
    expirationTime,
    sortIndex: -1,
  };
  newTask.sortIndex = expirationTime;
  push(taskQueue, newTask);
  requestHostCallback(flushWork);
  return newTask;
}

function flushWork(initialTime) {
  return workLoop(initialTime);
}

function shouldYieldToHost() {
  const timeElapsed = getCurrentTime() - startTime;
  if (timeElapsed < frameInterval) {
    return false;
  }
  return true;
}
function workLoop(initialTime) {
  let currentTime = initialTime;
  currentTask = peek(taskQueue);
  while (currentTask !== null) {
    if (currentTask.expirationTime > currentTime && shouldYieldToHost()) {
      break;
    }
    const callback = currentTask.callback;
    if (typeof callback === "function") {
      currentTask.callback = null;
      const didUserCallbackTimeout = currentTask.expirationTime <= currentTime;
      const continuationCallback = callback(didUserCallbackTimeout);
      currentTime = getCurrentTime();
      if (typeof continuationCallback === "function") {
        currentTask.callback = continuationCallback;
        return true;
      }
      if (currentTask === peek(taskQueue)) {
        pop(taskQueue);
      }
    } else {
      pop(taskQueue);
    }
    currentTask = peek(taskQueue);
  }
  if (currentTask !== null) {
    return true;
  }
  return false;
}

+function unstable_cancelCallback(task) {
+  task.callback = null;
+}

export {
  NormalPriority as unstable_NormalPriority,
  unstable_scheduleCallback,
  shouldYieldToHost as unstable_shouldYield,
+ unstable_cancelCallback,
+ getCurrentTime as unstable_now
};

41.3 Scheduler.js #

src\react-reconciler\src\Scheduler.js

import * as Scheduler from 'scheduler'
export const scheduleCallback = Scheduler.unstable_scheduleCallback
export const NormalPriority = Scheduler.unstable_NormalPriority
export const ImmediatePriority = Scheduler.unstable_ImmediatePriority;
export const UserBlockingPriority = Scheduler.unstable_UserBlockingPriority;
export const LowPriority = Scheduler.unstable_LowPriority;
export const IdlePriority = Scheduler.unstable_IdlePriority;
export const shouldYield = Scheduler.unstable_shouldYield
+export const cancelCallback = Scheduler.unstable_cancelCallback
+export const now = Scheduler.unstable_now;

41.4 ReactFiberWorkLoop.js #

src\react-reconciler\src\ReactFiberWorkLoop.js

import {
  scheduleCallback as Scheduler_scheduleCallback,
  ImmediatePriority as ImmediateSchedulerPriority,
  UserBlockingPriority as UserBlockingSchedulerPriority,
  NormalPriority as NormalSchedulerPriority,
  IdlePriority as IdleSchedulerPriority,
  shouldYield,
+ cancelCallback as Scheduler_cancelCallback,
+ now
} from "./Scheduler";
import { createWorkInProgress } from "./ReactFiber";
import { beginWork } from "./ReactFiberBeginWork";
import { completeWork } from "./ReactFiberCompleteWork";
import { MutationMask, NoFlags, Passive } from "./ReactFiberFlags";
import {
  commitMutationEffects,
  commitPassiveUnmountEffects,
  commitPassiveMountEffects,
  commitLayoutEffects,
} from "./ReactFiberCommitWork";
import { finishQueueingConcurrentUpdates } from "./ReactFiberConcurrentUpdates";
import {
  NoLane, markRootUpdated, NoLanes,
  getNextLanes, getHighestPriorityLane, SyncLane,
+ includesBlockingLane, markStarvedLanesAsExpired, includesExpiredLane,
+ mergeLanes, markRootFinished, NoTimestamp
} from './ReactFiberLane';
import {
  getCurrentUpdatePriority, lanesToEventPriority, DiscreteEventPriority, ContinuousEventPriority,
  DefaultEventPriority, IdleEventPriority, setCurrentUpdatePriority
} from './ReactEventPriorities';
import { getCurrentEventPriority } from 'react-dom-bindings/src/client/ReactDOMHostConfig';
import { scheduleSyncCallback, flushSyncCallbacks } from './ReactFiberSyncTaskQueue';

let workInProgress = null;
let rootDoesHavePassiveEffects = false;
let rootWithPendingPassiveEffects = null;
let workInProgressRootRenderLanes = NoLanes;

const RootInProgress = 0;
const RootCompleted = 5;
let workInProgressRoot = null;
let workInProgressRootExitStatus = RootInProgress;
+let currentEventTime = NoTimestamp;

+function cancelCallback(callbackNode) {
+  console.log('cancelCallback');
+  return Scheduler_cancelCallback(callbackNode);
+}

+export function scheduleUpdateOnFiber(root, fiber, lane, eventTime) {
  markRootUpdated(root, lane);
+ ensureRootIsScheduled(root, eventTime);
}
+function ensureRootIsScheduled(root, currentTime) {
  const existingCallbackNode = root.callbackNode;
+ markStarvedLanesAsExpired(root, currentTime);
  const nextLanes = getNextLanes(root, root === workInProgressRoot ? workInProgressRootRenderLanes : NoLanes);
  if (nextLanes === NoLanes) {
    root.callbackNode = null;
    root.callbackPriority = NoLane;
    return;
  }
  const newCallbackPriority = getHighestPriorityLane(nextLanes);
  const existingCallbackPriority = root.callbackPriority;
  if (existingCallbackPriority === newCallbackPriority) {
    return;
  }
  if (existingCallbackNode != null) {
    cancelCallback(existingCallbackNode);
  }
  let newCallbackNode;
  if (newCallbackPriority === SyncLane) {
    scheduleSyncCallback(performSyncWorkOnRoot.bind(null, root));
    queueMicrotask(flushSyncCallbacks);
    newCallbackNode = null;
  } else {
    let schedulerPriorityLevel;
    switch (lanesToEventPriority(nextLanes)) {
      case DiscreteEventPriority:
        schedulerPriorityLevel = ImmediateSchedulerPriority;
        break;
      case ContinuousEventPriority:
        schedulerPriorityLevel = UserBlockingSchedulerPriority;
        break;
      case DefaultEventPriority:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
      case IdleEventPriority:
        schedulerPriorityLevel = IdleSchedulerPriority;
        break;
      default:
        schedulerPriorityLevel = NormalSchedulerPriority;
        break;
    }
    newCallbackNode = Scheduler_scheduleCallback(schedulerPriorityLevel, performConcurrentWorkOnRoot.bind(null, root))
  }
  root.callbackPriority = newCallbackPriority;
  root.callbackNode = newCallbackNode;
}
function performSyncWorkOnRoot(root) {
  const lanes = getNextLanes(root, NoLanes);
  renderRootSync(root, lanes);
  const finishedWork = root.current.alternate
  root.finishedWork = finishedWork
  commitRoot(root)
  return null;
}
function performConcurrentWorkOnRoot(root, didTimeout) {
  const originalCallbackNode = root.callbackNode;
  const lanes = getNextLanes(root, NoLanes);
  if (lanes === NoLanes) {
    return null;
  }
+ const nonIncludesBlockingLane = !includesBlockingLane(root, lanes);
+ const nonIncludesExpiredLane = !includesExpiredLane(root, lanes);
+ const nonTimeout = !didTimeout;
+ const shouldTimeSlice = nonIncludesBlockingLane && nonIncludesExpiredLane && nonTimeout;
  const exitStatus = shouldTimeSlice ? renderRootConcurrent(root, lanes) : renderRootSync(root, lanes);
  if (exitStatus !== RootInProgress) {
    const finishedWork = root.current.alternate
    root.finishedWork = finishedWork
    commitRoot(root)
  }
  if (root.callbackNode === originalCallbackNode) {
    return performConcurrentWorkOnRoot.bind(null, root);
  }
  return null;
}
function renderRootConcurrent(root, lanes) {
 if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes);
  }
  workLoopConcurrent();
  if (workInProgress !== null) {
    return RootInProgress;
  }
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}
function workLoopConcurrent() {
  while (workInProgress !== null && !shouldYield()) {
+   sleep(5)
    performUnitOfWork(workInProgress);
  }
}
export function flushPassiveEffects() {
  if (rootWithPendingPassiveEffects !== null) {
    const root = rootWithPendingPassiveEffects;
    commitPassiveUnmountEffects(root.current);
    commitPassiveMountEffects(root, root.current);
  }
}
function commitRoot(root) {
  const previousPriority = getCurrentUpdatePriority();
  try {
    setCurrentUpdatePriority(DiscreteEventPriority);
    commitRootImpl(root);
  } finally {
    setCurrentUpdatePriority(previousPriority);
  }
}
function commitRootImpl(root) {
  const { finishedWork } = root;
+ console.log('commit', finishedWork.child.memoizedState.memoizedState[0]);
  root.callbackNode = null;
  root.callbackPriority = NoLane;
+ const remainingLanes = mergeLanes(finishedWork.lanes, finishedWork.childLanes);
+ markRootFinished(root, remainingLanes);
  if ((finishedWork.subtreeFlags & Passive) !== NoFlags || (finishedWork.flags & Passive) !== NoFlags) {
    if (!rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = true;
      Scheduler_scheduleCallback(NormalSchedulerPriority, flushPassiveEffects);
    }
  }
  const subtreeHasEffects = (finishedWork.subtreeFlags & MutationMask) !== NoFlags;
  const rootHasEffect = (finishedWork.flags & MutationMask) !== NoFlags;
  if (subtreeHasEffects || rootHasEffect) {
    commitMutationEffects(finishedWork, root);
    commitLayoutEffects(finishedWork, root);
    root.current = finishedWork;
    if (rootDoesHavePassiveEffects) {
      rootDoesHavePassiveEffects = false;
      rootWithPendingPassiveEffects = root;
    }
  }
  root.current = finishedWork;
+ ensureRootIsScheduled(root, now());
}
function prepareFreshStack(root, lanes) {
  workInProgressRoot = root;
  workInProgress = createWorkInProgress(root.current, null);
  workInProgressRootRenderLanes = lanes;
  finishQueueingConcurrentUpdates();
}
function renderRootSync(root, lanes) {
  if (workInProgressRoot !== root || workInProgressRootRenderLanes !== lanes) {
    prepareFreshStack(root, lanes)
  }
  workLoopSync();
  workInProgressRoot = null;
  workInProgressRootRenderLanes = NoLanes;
  return workInProgressRootExitStatus;
}

function workLoopSync() {
  while (workInProgress !== null) {
    performUnitOfWork(workInProgress);
  }
}
function performUnitOfWork(unitOfWork) {
  const current = unitOfWork.alternate;
  const next = beginWork(current, unitOfWork, workInProgressRootRenderLanes);
  unitOfWork.memoizedProps = unitOfWork.pendingProps;
  if (next === null) {
    completeUnitOfWork(unitOfWork);
  } else {
    workInProgress = next;
  }
}

function completeUnitOfWork(unitOfWork) {
  let completedWork = unitOfWork;
  do {
    const current = completedWork.alternate;
    const returnFiber = completedWork.return;
    completeWork(current, completedWork);
    const siblingFiber = completedWork.sibling;
    if (siblingFiber !== null) {
      workInProgress = siblingFiber;
      return;
    }
    completedWork = returnFiber;
    workInProgress = completedWork;
  } while (completedWork !== null);
  if (workInProgressRootExitStatus === RootInProgress) {
    workInProgressRootExitStatus = RootCompleted;
  }
}

export function requestUpdateLane() {
  const updateLane = getCurrentUpdatePriority();
  if (updateLane !== NoLane) {
    return updateLane;
  }
  const eventLane = getCurrentEventPriority();
  return eventLane;
}

+export function requestEventTime() {
+  currentEventTime = now();
+  return currentEventTime;
+}

+function sleep(time) {
+  const timeStamp = new Date().getTime();
+  const endTime = timeStamp + time;
+  while (true) {
+    if (new Date().getTime() > endTime) {
+      return;
+    }
+  }
+}

41.5 ReactFiberLane.js #

src\react-reconciler\src\ReactFiberLane.js

import { allowConcurrentByDefault } from 'shared/ReactFeatureFlags';

+export const NoTimestamp = -1;

export const TotalLanes = 31;
export const NoLanes = 0b0000000000000000000000000000000;
export const NoLane = 0b0000000000000000000000000000000;
export const SyncLane = 0b0000000000000000000000000000001;// 1
export const InputContinuousLane = 0b0000000000000000000000000000100;// 4
export const DefaultLane = 0b0000000000000000000000000010000;// 16
export const NonIdleLanes = 0b0001111111111111111111111111111;
export const IdleLane = 0b0100000000000000000000000000000;

export function mergeLanes(a, b) {
  return a | b;
}
export function markRootUpdated(root, updateLane) {
  root.pendingLanes |= updateLane;
}

export function getNextLanes(root, wipLanes) {
  const pendingLanes = root.pendingLanes;
  if (pendingLanes === NoLanes) {
    return NoLanes;
  }
  const nextLanes = getHighestPriorityLanes(pendingLanes);
  if (wipLanes !== NoLanes && wipLanes !== nextLanes) {
    if (nextLanes >= wipLanes) {
      return wipLanes;
    }
  }
  return nextLanes;
}

function getHighestPriorityLanes(lanes) {
  return getHighestPriorityLane(lanes);
}

export function getHighestPriorityLane(lanes) {
  return lanes & -lanes;
}

export function includesNonIdleWork(lanes) {
  return (lanes & NonIdleLanes) !== NoLanes;
}
export function includesBlockingLane(root, lanes) {
  if (allowConcurrentByDefault) {
    return false;
  }
  const SyncDefaultLanes = InputContinuousLane | DefaultLane;
  return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function isSubsetOfLanes(set, subset) {
  return (set & subset) === subset;
}


+function pickArbitraryLaneIndex(lanes) {
+  return 31 - Math.clz32(lanes);
+}
+
+export function markStarvedLanesAsExpired(root, currentTime) {
+  const pendingLanes = root.pendingLanes;
+  const expirationTimes = root.expirationTimes;
+  let lanes = pendingLanes
+  while (lanes > 0) {
+    const index = pickArbitraryLaneIndex(lanes);
+    const lane = 1 << index;
+    const expirationTime = expirationTimes[index];
+    if (expirationTime === NoTimestamp) {
+      expirationTimes[index] = computeExpirationTime(lane, currentTime);
+    } else if (expirationTime <= currentTime) {
+      root.expiredLanes |= lane;
+    }
+    lanes &= ~lane;
+  }
+}
+
+function computeExpirationTime(lane, currentTime) {
+  switch (lane) {
+    case SyncLane:
+    case InputContinuousLane:
+      return currentTime + 250;
+    case DefaultLane:
+      return currentTime + 5000;
+    case IdleLane:
+      return NoTimestamp;
+    default:
+      return NoTimestamp;
+  }
+}
+export function createLaneMap(initial) {
+  const laneMap = [];
+  for (let i = 0; i < TotalLanes; i++) {
+    laneMap.push(initial);
+  }
+  return laneMap;
+}
+export function includesExpiredLane(root, lanes) {
+  return (lanes & root.expiredLanes) !== NoLanes;
+}
+export function markRootFinished(root, remainingLanes) {
+  const noLongerPendingLanes = root.pendingLanes & ~remainingLanes;
+  root.pendingLanes = remainingLanes;
+  let lanes = noLongerPendingLanes;
+  const expirationTimes = root.expirationTimes;
+  while (lanes > 0) {
+    const index = pickArbitraryLaneIndex(lanes);
+    const lane = 1 << index;
+    expirationTimes[index] = NoTimestamp;
+    lanes &= ~lane;
+  }
+}

41.6 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

import { HostRoot, IndeterminateComponent, HostComponent, HostText } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
+import { NoLanes } from './ReactFiberLane';

export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.deletions = null;
  this.alternate = null;

  this.index = 0;
  this.ref = null;
+ this.lanes = NoLanes;
+ this.childLanes = NoLanes;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}
// We use a double buffering pooling technique because we know that we'll
// only ever need at most two versions of a tree. We pool the "other" unused
// node that we're free to reuse. This is lazily created to avoid allocating
// extra objects for things that are never updated. It also allow us to
// reclaim the extra memory if needed.
//我们使用双缓冲池技术，因为我们知道一棵树最多只需要两个版本
//我们将“其他”未使用的我们可以自由重用的节点
//这是延迟创建的，以避免分配从未更新的内容的额外对象。它还允许我们如果需要，回收额外的内存
export function createWorkInProgress(current, pendingProps) {
  let workInProgress = current.alternate;
  if (workInProgress === null) {
    workInProgress = createFiber(current.tag, pendingProps, current.key);
    workInProgress.type = current.type;
    workInProgress.stateNode = current.stateNode;
    workInProgress.alternate = current;
    current.alternate = workInProgress;
  } else {
    workInProgress.pendingProps = pendingProps;
    workInProgress.type = current.type;
    workInProgress.flags = NoFlags;
    workInProgress.subtreeFlags = NoFlags;
+   workInProgress.deletions = null;
  }
  workInProgress.child = current.child;
  workInProgress.memoizedProps = current.memoizedProps;
  workInProgress.memoizedState = current.memoizedState;
  workInProgress.updateQueue = current.updateQueue;
  workInProgress.sibling = current.sibling;
  workInProgress.index = current.index;
  workInProgress.ref = current.ref;
+ workInProgress.flags = current.flags;
+ workInProgress.childLanes = current.childLanes;
+ workInProgress.lanes = current.lanes;
  return workInProgress;
}
export function createFiberFromTypeAndProps(type, key, pendingProps) {
  let fiberTag = IndeterminateComponent;
  if (typeof type === "string") {
    fiberTag = HostComponent;
  }
  const fiber = createFiber(fiberTag, pendingProps, key);
  fiber.type = type;
  return fiber;
}
export function createFiberFromElement(element) {
  const { type } = element;
  const { key } = element;
  const pendingProps = element.props;
  const fiber = createFiberFromTypeAndProps(type, key, pendingProps);
  return fiber;
}

export function createFiberFromText(content) {
  const fiber = createFiber(HostText, content, null);
  return fiber;
}

41.7 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import { HostRoot, HostComponent, HostText, IndeterminateComponent, FunctionComponent } from "./ReactWorkTags";
import { processUpdateQueue, cloneUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { renderWithHooks } from "react-reconciler/src/ReactFiberHooks";
+import { NoLanes } from './ReactFiberLane';

function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(workInProgress, current.child, nextChildren);
  }
}
function updateHostRoot(current, workInProgress, renderLanes) {
  const nextProps = workInProgress.pendingProps;
  cloneUpdateQueue(current, workInProgress);
  processUpdateQueue(workInProgress, nextProps, renderLanes)
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function mountIndeterminateComponent(_current, workInProgress, Component) {
  const props = workInProgress.pendingProps;
  const value = renderWithHooks(null, workInProgress, Component, props);
  workInProgress.tag = FunctionComponent;
  reconcileChildren(null, workInProgress, value);
  return workInProgress.child;
}
+function updateFunctionComponent(current, workInProgress, Component, nextProps, renderLanes) {
+ const nextChildren = renderWithHooks(current, workInProgress, Component, nextProps, renderLanes);
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
export function beginWork(current, workInProgress, renderLanes) {
+ workInProgress.lanes = NoLanes;
  switch (workInProgress.tag) {
    case IndeterminateComponent: {
      return mountIndeterminateComponent(current, workInProgress, workInProgress.type, renderLanes);
    }
    case FunctionComponent: {
      const Component = workInProgress.type;
      const resolvedProps = workInProgress.pendingProps;
+     return updateFunctionComponent(current, workInProgress, Component, resolvedProps, renderLanes);
    }
    case HostRoot:
      return updateHostRoot(current, workInProgress, renderLanes);
    case HostComponent:
      return updateHostComponent(current, workInProgress, renderLanes);
    case HostText:
    default:
      return null;
  }
}

41.8 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
  prepareUpdate,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HostComponent, HostRoot, HostText, FunctionComponent } from "./ReactWorkTags";
import { Ref, NoFlags, Update } from "./ReactFiberFlags";
+import { NoLanes, mergeLanes } from './ReactFiberLane';

function markRef(workInProgress) {
  workInProgress.flags |= Ref;
}

function bubbleProperties(completedWork) {
+ let newChildLanes = NoLanes;
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
+   newChildLanes = mergeLanes(newChildLanes, mergeLanes(child.lanes, child.childLanes));
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
+ completedWork.childLanes = newChildLanes;
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}
function markUpdate(workInProgress) {
  workInProgress.flags |= Update;
}
function updateHostComponent(current, workInProgress, type, newProps) {
  const oldProps = current.memoizedProps;
  const instance = workInProgress.stateNode;
  const updatePayload = prepareUpdate(instance, type, oldProps, newProps);
  workInProgress.updateQueue = updatePayload;
  if (updatePayload) {
    markUpdate(workInProgress);
  }
}
export function completeWork(current, workInProgress) {
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
      if (current !== null && workInProgress.stateNode != null) {
        updateHostComponent(current, workInProgress, type, newProps);
        if (current.ref !== workInProgress.ref) {
          markRef(workInProgress);
        }
      } else {
        const instance = createInstance(type, newProps, workInProgress);
        appendAllChildren(instance, workInProgress);
        workInProgress.stateNode = instance;
        finalizeInitialChildren(instance, type, newProps);
        if (workInProgress.ref !== null) {
          markRef(workInProgress);
        }
      }
      bubbleProperties(workInProgress);
      return null;
    }
    case FunctionComponent:
      bubbleProperties(workInProgress);
      break;
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
    default:
      break;
  }
}

41.9 ReactFiberConcurrentUpdates.js #

src\react-reconciler\src\ReactFiberConcurrentUpdates.js

import { HostRoot } from "./ReactWorkTags";
+import { mergeLanes, NoLanes } from './ReactFiberLane';

const concurrentQueues = [];
let concurrentQueuesIndex = 0;

export function markUpdateLaneFromFiberToRoot(sourceFiber) {
  let node = sourceFiber;
  let parent = sourceFiber.return;
  while (parent !== null) {
    node = parent;
    parent = parent.return;
  }
  if (node.tag === HostRoot) {
    const root = node.stateNode;
    return root;
  }
  return null;
}
export function enqueueConcurrentHookUpdate(fiber, queue, update, lane) {
  enqueueUpdate(fiber, queue, update, lane);
  return getRootForUpdatedFiber(fiber);
}
export function enqueueConcurrentClassUpdate(fiber, queue, update, lane) {
  enqueueUpdate(fiber, queue, update, lane);
  return getRootForUpdatedFiber(fiber);
}

function enqueueUpdate(fiber, queue, update, lane) {
  concurrentQueues[concurrentQueuesIndex++] = fiber;
  concurrentQueues[concurrentQueuesIndex++] = queue;
  concurrentQueues[concurrentQueuesIndex++] = update;
  concurrentQueues[concurrentQueuesIndex++] = lane;
+ fiber.lanes = mergeLanes(fiber.lanes, lane);
}
function getRootForUpdatedFiber(sourceFiber) {
  let node = sourceFiber;
  let parent = node.return;
  while (parent !== null) {
    node = parent;
    parent = node.return;
  }
  return node.tag === HostRoot ? node.stateNode : null;
}

export function finishQueueingConcurrentUpdates() {
  const endIndex = concurrentQueuesIndex;
  concurrentQueuesIndex = 0;
  let i = 0;
  while (i < endIndex) {
    const fiber = concurrentQueues[i++];
    const queue = concurrentQueues[i++];
    const update = concurrentQueues[i++];
    const lane = concurrentQueues[i++]
    if (queue !== null && update !== null) {
      const pending = queue.pending;
      if (pending === null) {
        update.next = update;
      } else {
        update.next = pending.next;
        pending.next = update;
      }
      queue.pending = update;
    }
  }
}

41.10 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
+import { scheduleUpdateOnFiber, requestUpdateLane, requestEventTime } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";
+import { NoLanes, NoLane, mergeLanes, isSubsetOfLanes } from './ReactFiberLane';

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;
+let renderLanes = NoLanes;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
  useLayoutEffect: mountLayoutEffect,
  useRef: mountRef,
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
  useLayoutEffect: updateLayoutEffect,
  useRef: updateRef
};
function mountRef(initialValue) {
  const hook = mountWorkInProgressHook();
  const ref = {
    current: initialValue,
  };
  hook.memoizedState = ref;
  return ref;
}
function updateRef() {
  const hook = updateWorkInProgressHook();
  return hook.memoizedState;
}
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
function updateLayoutEffect(create, deps) {
  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
}
function mountLayoutEffect(create, deps) {
  const fiberFlags = UpdateEffect;
  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
}
function updateEffect(create, deps) {
  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
+   lastRenderedReducer: reducer,
+   lastRenderedState: initialArg
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
+  const hook = updateWorkInProgressHook();
+  const queue = hook.queue;
+  queue.lastRenderedReducer = reducer;
+  const current = currentHook;
+  let baseQueue = current.baseQueue;
+  const pendingQueue = queue.pending;
+  if (pendingQueue !== null) {
+    if (baseQueue !== null) {
+      const baseFirst = baseQueue.next;
+      const pendingFirst = pendingQueue.next;
+      baseQueue.next = pendingFirst;
+      pendingQueue.next = baseFirst;
+    }
+    current.baseQueue = baseQueue = pendingQueue;
+    queue.pending = null;
+  }
+  if (baseQueue !== null) {
+    printQueue(baseQueue)
+    const first = baseQueue.next;
+    let newState = current.baseState;
+    let newBaseState = null;
+    let newBaseQueueFirst = null;
+    let newBaseQueueLast = null;
+    let update = first;
+    do {
+      const updateLane = update.lane;
+      const shouldSkipUpdate = !isSubsetOfLanes(renderLanes, updateLane);
+      if (shouldSkipUpdate) {
+        const clone = {
+          lane: updateLane,
+          action: update.action,
+          hasEagerState: update.hasEagerState,
+          eagerState: update.eagerState,
+          next: null,
+        };
+        if (newBaseQueueLast === null) {
+          newBaseQueueFirst = newBaseQueueLast = clone;
+          newBaseState = newState;
+        } else {
+          newBaseQueueLast = newBaseQueueLast.next = clone;
+        }
+        currentlyRenderingFiber.lanes = mergeLanes(currentlyRenderingFiber.lanes, updateLane);
+      } else {
+        if (newBaseQueueLast !== null) {
+          const clone = {
+            lane: NoLane,
+            action: update.action,
+            hasEagerState: update.hasEagerState,
+            eagerState: update.eagerState,
+            next: null,
+          };
+          newBaseQueueLast = newBaseQueueLast.next = clone;
+        }
+        if (update.hasEagerState) {
+          newState = update.eagerState;
+        } else {
+          const action = update.action;
+          newState = reducer(newState, action);
+        }
+      }
+      update = update.next;
+    } while (update !== null && update !== first);
+    if (newBaseQueueLast === null) {
+      newBaseState = newState;
+    } else {
+      newBaseQueueLast.next = newBaseQueueFirst;
+    }
+    hook.memoizedState = newState;
+    hook.baseState = newBaseState;
+    hook.baseQueue = newBaseQueueLast;
+    queue.lastRenderedState = newState;
+  }
+  if (baseQueue === null) {
+    queue.lanes = NoLanes;
+  }
+  const dispatch = queue.dispatch;
+  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const lane = requestUpdateLane(fiber);
  const update = {
    lane,
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const alternate = fiber.alternate;
  if (fiber.lanes === NoLanes && (alternate === null || alternate.lanes === NoLanes)) {
    const lastRenderedReducer = queue.lastRenderedReducer;
    const currentState = queue.lastRenderedState;
    const eagerState = lastRenderedReducer(currentState, action);
    update.hasEagerState = true;
    update.eagerState = eagerState;
    if (is(eagerState, currentState)) {
      return;
    }
  }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update, lane);
+ const eventTime = requestEventTime();
+ scheduleUpdateOnFiber(root, fiber, lane, eventTime);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
+   baseState: null,
+   baseQueue: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
+     baseState: currentHook.baseState,
+     baseQueue: currentHook.baseQueue,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props, nextRenderLanes) {
+ renderLanes = nextRenderLanes;
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
+ workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
+ renderLanes = NoLanes;
  return children;
}

+function printQueue(queue) {
+  const first = queue.next;
+  let desc = '';
+  let update = first;
+  do {
+    desc += ("=>" + (update.action.id));
+    update = update.next;
+  } while (update !== null && update !== first);
+  desc += "=>null";
+  console.log(desc);
+}

41.11 ReactFiberReconciler.js #

src\react-reconciler\src\ReactFiberReconciler.js

import { createFiberRoot } from "./ReactFiberRoot";
import { createUpdate, enqueueUpdate } from "./ReactFiberClassUpdateQueue";
+import { scheduleUpdateOnFiber, requestUpdateLane, requestEventTime } from "./ReactFiberWorkLoop";
export function createContainer(containerInfo) {
  return createFiberRoot(containerInfo);
}
export function updateContainer(element, container) {
  const current = container.current;
+ const eventTime = requestEventTime();
  const lane = requestUpdateLane(current);
  const update = createUpdate(lane);
  update.payload = { element };
  const root = enqueueUpdate(current, update, lane);
+ scheduleUpdateOnFiber(root, current, lane, eventTime);
}

41.12 ReactFiberRoot.js #

src\react-reconciler\src\ReactFiberRoot.js

import { createHostRootFiber } from "./ReactFiber";
import { initializeUpdateQueue } from "./ReactFiberClassUpdateQueue";
+import { NoTimestamp, createLaneMap, NoLanes } from 'react-reconciler/src/ReactFiberLane';

function FiberRootNode(containerInfo) {
  this.containerInfo = containerInfo;
+ this.expirationTimes = createLaneMap(NoTimestamp);
+ this.expiredLanes = NoLanes;
}

export function createFiberRoot(containerInfo) {
  const root = new FiberRootNode(containerInfo);
  const uninitializedFiber = createHostRootFiber();
  root.current = uninitializedFiber;
  uninitializedFiber.stateNode = root;
  initializeUpdateQueue(uninitializedFiber);
  return root;
}

42.context #

42.1 src\main.jsx #

src\main.jsx

import * as React from "react";
import { createRoot } from "react-dom/client";

+const NameContext = React.createContext('');
+const AgeContext = React.createContext('');
+
+function Child() {
+  const name = React.useContext(NameContext);
+  const age = React.useContext(AgeContext);
+  return <button>{name + age}</button>
+}
+function App() {
+  const [name, setName] = React.useState('a');
+  const [age, setAge] = React.useState('1');
+  return (
+    <div>
+      <button onClick={() => {
+        setName(name + 'a')
+      }}>setName</button>
+      <button onClick={() => {
+        setAge(age + '1')
+      }}>setAge</button>
+      <NameContext.Provider value={name}>
+        <AgeContext.Provider value={age}>
+          <Child />
+        </AgeContext.Provider>
+      </NameContext.Provider>
+    </div>
+  )
+}

const element = <App />;
const container = document.getElementById("root");
const root = createRoot(container, { unstable_concurrentUpdatesByDefault: true });
root.render(element);

42.2 react\index.js #

src\react\index.js

export {
  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
  useReducer,
  useState,
  useEffect,
  useLayoutEffect,
  useRef,
+ createContext,
+ useContext,
} from "./src/React";

42.3 React.js #

src\react\src\React.js

+import { useReducer, useState, useEffect, useLayoutEffect, useRef, useContext } from "./ReactHooks";
import ReactSharedInternals from "./ReactSharedInternals";
+import { createContext } from './ReactContext';

export {
  useReducer,
  useState,
  useEffect,
  useLayoutEffect,
  useRef,
+ createContext,
+ useContext,
  ReactSharedInternals as __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
};

42.4 ReactContext.js #

src\react\src\ReactContext.js

import { REACT_PROVIDER_TYPE, REACT_CONTEXT_TYPE } from 'shared/ReactSymbols';

export function createContext(defaultValue) {
  const context = {
    $$typeof: REACT_CONTEXT_TYPE,
    _currentValue: defaultValue,
    Provider: null
  };
  context.Provider = {
    $$typeof: REACT_PROVIDER_TYPE,
    _context: context
  };
  return context;
}

42.5 ReactHooks.js #

src\react\src\ReactHooks.js

import ReactCurrentDispatcher from "./ReactCurrentDispatcher";

function resolveDispatcher() {
  const dispatcher = ReactCurrentDispatcher.current;
  return dispatcher;
}

export function useReducer(reducer, initialArg, init) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useReducer(reducer, initialArg, init);
}

export function useState(initialState) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useState(initialState);
}

export function useEffect(create, deps) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useEffect(create, deps);
}
export function useLayoutEffect(create, deps) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useLayoutEffect(create, deps);
}
export function useRef(initialValue) {
  const dispatcher = resolveDispatcher();
  return dispatcher.useRef(initialValue);
}
+export function useContext(Context) {
+  const dispatcher = resolveDispatcher();
+  return dispatcher.useContext(Context);
+}

42.6 ReactFiber.js #

src\react-reconciler\src\ReactFiber.js

+import { HostRoot, IndeterminateComponent, HostComponent, HostText, ContextProvider } from "./ReactWorkTags";
import { NoFlags } from "./ReactFiberFlags";
import { NoLanes } from './ReactFiberLane';
+import { REACT_PROVIDER_TYPE } from 'shared/ReactSymbols';

export function FiberNode(tag, pendingProps, key) {
  this.tag = tag;
  this.key = key;
  this.type = null;
  this.stateNode = null;

  this.return = null;
  this.child = null;
  this.sibling = null;

  this.pendingProps = pendingProps;
  this.memoizedProps = null;
  this.updateQueue = null;
  this.memoizedState = null;

  this.flags = NoFlags;
  this.subtreeFlags = NoFlags;
  this.deletions = null;
  this.alternate = null;

  this.index = 0;
  this.ref = null;
  this.lanes = NoLanes;
  this.childLanes = NoLanes;
}
function createFiber(tag, pendingProps, key) {
  return new FiberNode(tag, pendingProps, key);
}
export function createHostRootFiber() {
  return createFiber(HostRoot, null, null);
}
// We use a double buffering pooling technique because we know that we'll
// only ever need at most two versions of a tree. We pool the "other" unused
// node that we're free to reuse. This is lazily created to avoid allocating
// extra objects for things that are never updated. It also allow us to
// reclaim the extra memory if needed.
//我们使用双缓冲池技术，因为我们知道一棵树最多只需要两个版本
//我们将“其他”未使用的我们可以自由重用的节点
//这是延迟创建的，以避免分配从未更新的内容的额外对象。它还允许我们如果需要，回收额外的内存
export function createWorkInProgress(current, pendingProps) {
  let workInProgress = current.alternate;
  if (workInProgress === null) {
    workInProgress = createFiber(current.tag, pendingProps, current.key);
    workInProgress.type = current.type;
    workInProgress.stateNode = current.stateNode;
    workInProgress.alternate = current;
    current.alternate = workInProgress;
  } else {
    workInProgress.pendingProps = pendingProps;
    workInProgress.type = current.type;
    workInProgress.flags = NoFlags;
    workInProgress.subtreeFlags = NoFlags;
    workInProgress.deletions = null;
  }
  workInProgress.child = current.child;
  workInProgress.memoizedProps = current.memoizedProps;
  workInProgress.memoizedState = current.memoizedState;
  workInProgress.updateQueue = current.updateQueue;
  workInProgress.sibling = current.sibling;
  workInProgress.index = current.index;
  workInProgress.ref = current.ref;
  workInProgress.flags = current.flags;
  workInProgress.childLanes = current.childLanes;
  workInProgress.lanes = current.lanes;
  return workInProgress;
}
export function createFiberFromTypeAndProps(type, key, pendingProps) {
  let fiberTag = IndeterminateComponent;
  if (typeof type === "string") {
    fiberTag = HostComponent;
  } else {
+   getTag: switch (type) {
+     default:
+       {
+         if (typeof type === 'object' && type !== null) {
+           switch (type.$$typeof) {
+             case REACT_PROVIDER_TYPE:
+               fiberTag = ContextProvider;
+               break getTag;
+             default:
+               break;
+           }
+         }
+       }
+   }
  }
  const fiber = createFiber(fiberTag, pendingProps, key);
  fiber.type = type;
  return fiber;
}
export function createFiberFromElement(element) {
  const { type } = element;
  const { key } = element;
  const pendingProps = element.props;
  const fiber = createFiberFromTypeAndProps(type, key, pendingProps);
  return fiber;
}

export function createFiberFromText(content) {
  const fiber = createFiber(HostText, content, null);
  return fiber;
}

42.7 ReactFiberBeginWork.js #

src\react-reconciler\src\ReactFiberBeginWork.js

import {
  HostRoot, HostComponent, HostText, IndeterminateComponent,
+ FunctionComponent, ContextProvider
} from "./ReactWorkTags";
import { processUpdateQueue, cloneUpdateQueue } from "./ReactFiberClassUpdateQueue";
import { mountChildFibers, reconcileChildFibers } from "./ReactChildFiber";
import { shouldSetTextContent } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { renderWithHooks } from "react-reconciler/src/ReactFiberHooks";
import { NoLanes } from './ReactFiberLane';
+import { pushProvider } from './ReactFiberNewContext';

function reconcileChildren(current, workInProgress, nextChildren) {
  if (current === null) {
    workInProgress.child = mountChildFibers(workInProgress, null, nextChildren);
  } else {
    workInProgress.child = reconcileChildFibers(workInProgress, current.child, nextChildren);
  }
}
function updateHostRoot(current, workInProgress, renderLanes) {
  const nextProps = workInProgress.pendingProps;
  cloneUpdateQueue(current, workInProgress);
  processUpdateQueue(workInProgress, nextProps, renderLanes)
  const nextState = workInProgress.memoizedState;
  const nextChildren = nextState.element;
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function updateHostComponent(current, workInProgress) {
  const { type } = workInProgress;
  const nextProps = workInProgress.pendingProps;
  let nextChildren = nextProps.children;
  const isDirectTextChild = shouldSetTextContent(type, nextProps);
  if (isDirectTextChild) {
    nextChildren = null;
  }
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
function mountIndeterminateComponent(_current, workInProgress, Component) {
  const props = workInProgress.pendingProps;
  const value = renderWithHooks(null, workInProgress, Component, props);
  workInProgress.tag = FunctionComponent;
  reconcileChildren(null, workInProgress, value);
  return workInProgress.child;
}
function updateFunctionComponent(current, workInProgress, Component, nextProps, renderLanes) {
  const nextChildren = renderWithHooks(current, workInProgress, Component, nextProps, renderLanes);
  reconcileChildren(current, workInProgress, nextChildren);
  return workInProgress.child;
}
export function beginWork(current, workInProgress, renderLanes) {
  workInProgress.lanes = NoLanes;
  switch (workInProgress.tag) {
    case IndeterminateComponent: {
      return mountIndeterminateComponent(current, workInProgress, workInProgress.type, renderLanes);
    }
    case FunctionComponent: {
      const Component = workInProgress.type;
      const resolvedProps = workInProgress.pendingProps;
      return updateFunctionComponent(current, workInProgress, Component, resolvedProps, renderLanes);
    }
    case HostRoot:
      return updateHostRoot(current, workInProgress, renderLanes);
    case HostComponent:
      return updateHostComponent(current, workInProgress, renderLanes);
    case HostText:
      return null;
+   case ContextProvider:
+     return updateContextProvider(current, workInProgress, renderLanes);
    default:
      return null;
  }
}

+function updateContextProvider(current, workInProgress, renderLanes) {
+  const providerType = workInProgress.type;
+  const context = providerType._context;
+  const newProps = workInProgress.pendingProps;
+  const newValue = newProps.value;
+  pushProvider(context, newValue);
+  const newChildren = newProps.children;
+  reconcileChildren(current, workInProgress, newChildren, renderLanes);
+  return workInProgress.child;
+}

42.8 ReactFiberCompleteWork.js #

src\react-reconciler\src\ReactFiberCompleteWork.js

import {
  appendInitialChild,
  createInstance,
  createTextInstance,
  finalizeInitialChildren,
  prepareUpdate,
} from "react-dom-bindings/src/client/ReactDOMHostConfig";
+import { HostComponent, HostRoot, HostText, FunctionComponent, ContextProvider } from "./ReactWorkTags";
import { Ref, NoFlags, Update } from "./ReactFiberFlags";
import { NoLanes, mergeLanes } from './ReactFiberLane';

function markRef(workInProgress) {
  workInProgress.flags |= Ref;
}

function bubbleProperties(completedWork) {
  let newChildLanes = NoLanes;
  let subtreeFlags = NoFlags;
  let child = completedWork.child;
  while (child !== null) {
    newChildLanes = mergeLanes(newChildLanes, mergeLanes(child.lanes, child.childLanes));
    subtreeFlags |= child.subtreeFlags;
    subtreeFlags |= child.flags;
    child = child.sibling;
  }
  completedWork.childLanes = newChildLanes;
  completedWork.subtreeFlags |= subtreeFlags;
}

function appendAllChildren(parent, workInProgress) {
  // 我们只有创建的顶级fiber，但需要递归其子节点来查找所有终端节点
  let node = workInProgress.child;
  while (node !== null) {
    // 如果是原生节点，直接添加到父节点上
    if (node.tag === HostComponent || node.tag === HostText) {
      appendInitialChild(parent, node.stateNode);
      // 再看看第一个节节点是不是原生节点
    } else if (node.child !== null) {
      // node.child.return = node
      node = node.child;
      continue;
    }
    if (node === workInProgress) {
      return;
    }
    // 如果没有弟弟就找父亲的弟弟
    while (node.sibling === null) {
      // 如果找到了根节点或者回到了原节点结束
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    // 下一个弟弟节点
    node = node.sibling;
  }
}
function markUpdate(workInProgress) {
  workInProgress.flags |= Update;
}
function updateHostComponent(current, workInProgress, type, newProps) {
  const oldProps = current.memoizedProps;
  const instance = workInProgress.stateNode;
  const updatePayload = prepareUpdate(instance, type, oldProps, newProps);
  workInProgress.updateQueue = updatePayload;
  if (updatePayload) {
    markUpdate(workInProgress);
  }
}
export function completeWork(current, workInProgress) {
  const newProps = workInProgress.pendingProps;
  switch (workInProgress.tag) {
    case HostComponent: {
      const { type } = workInProgress;
      if (current !== null && workInProgress.stateNode != null) {
        updateHostComponent(current, workInProgress, type, newProps);
        if (current.ref !== workInProgress.ref) {
          markRef(workInProgress);
        }
      } else {
        const instance = createInstance(type, newProps, workInProgress);
        appendAllChildren(instance, workInProgress);
        workInProgress.stateNode = instance;
        finalizeInitialChildren(instance, type, newProps);
        if (workInProgress.ref !== null) {
          markRef(workInProgress);
        }
      }
      bubbleProperties(workInProgress);
      return null;
    }
    case FunctionComponent:
      bubbleProperties(workInProgress);
      break;
    case HostRoot:
      bubbleProperties(workInProgress);
      break;
    case HostText: {
      const newText = newProps;
      workInProgress.stateNode = createTextInstance(newText);
      bubbleProperties(workInProgress);
      break;
    }
+   case ContextProvider: {
+     bubbleProperties(workInProgress);
+     break;
+   }
    default:
      break;
  }
}

42.9 ReactFiberCommitWork.js #

src\react-reconciler\src\ReactFiberCommitWork.js

+import { HostRoot, HostComponent, HostText, FunctionComponent, ContextProvider } from "./ReactWorkTags";
import { Passive, MutationMask, Placement, Update, LayoutMask, Ref } from "./ReactFiberFlags";
import { insertBefore, appendChild, commitUpdate, removeChild } from "react-dom-bindings/src/client/ReactDOMHostConfig";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";

export function commitMutationEffects(finishedWork, root) {
  commitMutationEffectsOnFiber(finishedWork, root);
}
export function commitPassiveUnmountEffects(finishedWork) {
  commitPassiveUnmountOnFiber(finishedWork);
}
function commitPassiveUnmountOnFiber(finishedWork) {
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      if (finishedWork.flags & Passive) {
        commitHookPassiveUnmountEffects(finishedWork, finishedWork.return, HookPassive | HookHasEffect);
      }
      break;
    }
    default: {
      recursivelyTraversePassiveUnmountEffects(finishedWork);
      break;
    }
  }
}
function recursivelyTraversePassiveUnmountEffects(parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveUnmountOnFiber(child);
      child = child.sibling;
    }
  }
}
function commitHookPassiveUnmountEffects(finishedWork, nearestMountedAncestor, hookFlags) {
  commitHookEffectListUnmount(hookFlags, finishedWork, nearestMountedAncestor);
}

function commitHookEffectListUnmount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const destroy = effect.destroy;
        effect.destroy = undefined;
        if (destroy !== undefined) {
          destroy();
        }
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}

export function commitPassiveMountEffects(root, finishedWork) {
  commitPassiveMountOnFiber(root, finishedWork);
}
function commitPassiveMountOnFiber(finishedRoot, finishedWork) {
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      if (flags & Passive) {
        commitHookPassiveMountEffects(finishedWork, HookPassive | HookHasEffect);
      }
      break;
    }
    case HostRoot: {
      recursivelyTraversePassiveMountEffects(finishedRoot, finishedWork);
      break;
    }
    default:
      break;
  }
}
function commitHookPassiveMountEffects(finishedWork, hookFlags) {
  commitHookEffectListMount(hookFlags, finishedWork);
}
function commitHookEffectListMount(flags, finishedWork) {
  const updateQueue = finishedWork.updateQueue;
  const lastEffect = updateQueue !== null ? updateQueue.lastEffect : null;
  if (lastEffect !== null) {
    const firstEffect = lastEffect.next;
    let effect = firstEffect;
    do {
      if ((effect.tag & flags) === flags) {
        const create = effect.create;
        effect.destroy = create();
      }
      effect = effect.next;
    } while (effect !== firstEffect);
  }
}
function recursivelyTraversePassiveMountEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & Passive) {
    let child = parentFiber.child;
    while (child !== null) {
      commitPassiveMountOnFiber(root, child);
      child = child.sibling;
    }
  }
}
let hostParent = null;
function commitDeletionEffects(root, returnFiber, deletedFiber) {
  let parent = returnFiber;
  findParent: while (parent !== null) {
    switch (parent.tag) {
      case HostComponent: {
        hostParent = parent.stateNode;
        break findParent;
      }
      case HostRoot: {
        hostParent = parent.stateNode.containerInfo;
        break findParent;
      }
      default:
        break;
    }
    parent = parent.return;
  }
  commitDeletionEffectsOnFiber(root, returnFiber, deletedFiber);
  hostParent = null;
}
function commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, deletedFiber) {
  switch (deletedFiber.tag) {
    case HostComponent:
    case HostText: {
      recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, deletedFiber);
      if (hostParent !== null) {
        removeChild(hostParent, deletedFiber.stateNode);
      }
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseDeletionEffects(finishedRoot, nearestMountedAncestor, parent) {
  let child = parent.child;
  while (child !== null) {
    commitDeletionEffectsOnFiber(finishedRoot, nearestMountedAncestor, child);
    child = child.sibling;
  }
}
function recursivelyTraverseMutationEffects(root, parentFiber) {
  const deletions = parentFiber.deletions;
  if (deletions !== null) {
    for (let i = 0; i < deletions.length; i++) {
      const childToDelete = deletions[i];
      commitDeletionEffects(root, parentFiber, childToDelete);
    }
  }
  if (parentFiber.subtreeFlags & MutationMask) {
    let { child } = parentFiber;
    while (child !== null) {
      commitMutationEffectsOnFiber(child, root);
      child = child.sibling;
    }
  }
}
function isHostParent(fiber) {
  return fiber.tag === HostComponent || fiber.tag === HostRoot;
}
function getHostParentFiber(fiber) {
  let parent = fiber.return;
  while (parent !== null) {
    if (isHostParent(parent)) {
      return parent;
    }
    parent = parent.return;
  }
  return parent;
}
function insertOrAppendPlacementNode(node, before, parent) {
  const { tag } = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost) {
    const { stateNode } = node;
    if (before) {
      insertBefore(parent, stateNode, before);
    } else {
      appendChild(parent, stateNode);
    }
  } else {
    const { child } = node;
    if (child !== null) {
      insertOrAppendPlacementNode(child, before, parent);
      let { sibling } = child;
      while (sibling !== null) {
        insertOrAppendPlacementNode(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}
function getHostSibling(fiber) {
  let node = fiber;
  siblings: while (true) {
    // 如果我们没有找到任何东西，让我们试试下一个弟弟
    while (node.sibling === null) {
      if (node.return === null || isHostParent(node.return)) {
        // 如果我们是根Fiber或者父亲是原生节点，我们就是最后的弟弟
        return null;
      }
      node = node.return;
    }
    // node.sibling.return = node.return
    node = node.sibling;
    while (node.tag !== HostComponent && node.tag !== HostText) {
      // 如果它不是原生节点，并且，我们可能在其中有一个原生节点
      // 试着向下搜索，直到找到为止
      if (node.flags & Placement) {
        // 如果我们没有孩子，可以试试弟弟
        continue siblings;
      } else {
        // node.child.return = node
        node = node.child;
      }
    } // Check if this host node is stable or about to be placed.
    // 检查此原生节点是否稳定可以放置
    if (!(node.flags & Placement)) {
      // 找到它了!
      return node.stateNode;
    }
  }
}
function commitPlacement(finishedWork) {
  const parentFiber = getHostParentFiber(finishedWork);
  switch (parentFiber.tag) {
    case HostComponent: {
      const parent = parentFiber.stateNode;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    case HostRoot: {
      const parent = parentFiber.stateNode.containerInfo;
      const before = getHostSibling(finishedWork);
      insertOrAppendPlacementNode(finishedWork, before, parent);
      break;
    }
    default:
      break;
  }
}
function commitReconciliationEffects(finishedWork) {
  const { flags } = finishedWork;
  if (flags & Placement) {
    commitPlacement(finishedWork);
    finishedWork.flags &= ~Placement;
  }
}
export function commitMutationEffectsOnFiber(finishedWork, root) {
  const current = finishedWork.alternate;
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case HostRoot: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
    case FunctionComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Update) {
        commitHookEffectListUnmount(HookLayout | HookHasEffect, finishedWork, finishedWork.return);
      }
      break;
    }
    case HostComponent: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      if (flags & Ref) {
        commitAttachRef(finishedWork);
      }
      if (flags & Update) {
        const instance = finishedWork.stateNode;
        if (instance != null) {
          const newProps = finishedWork.memoizedProps;
          const oldProps = current !== null ? current.memoizedProps : newProps;
          const type = finishedWork.type;
          const updatePayload = finishedWork.updateQueue;
          finishedWork.updateQueue = null;
          if (updatePayload !== null) {
            commitUpdate(instance, updatePayload, type, oldProps, newProps, finishedWork);
          }
        }
      }

      break;
    }
    case HostText: {
      recursivelyTraverseMutationEffects(root, finishedWork);
      commitReconciliationEffects(finishedWork);
      break;
    }
+   case ContextProvider: {
+     recursivelyTraverseMutationEffects(root, finishedWork);
+     commitReconciliationEffects(finishedWork);
+     break;
    }
    default: {
      break;
    }
  }
}
function commitAttachRef(finishedWork) {
  const ref = finishedWork.ref;
  if (ref !== null) {
    const instance = finishedWork.stateNode;
    if (typeof ref === "function") {
      ref(instance)
    } else {
      ref.current = instance;
    }
  }
}
export function commitLayoutEffects(finishedWork, root) {
  const current = finishedWork.alternate;
  commitLayoutEffectOnFiber(root, current, finishedWork);
}
function commitLayoutEffectOnFiber(finishedRoot, current, finishedWork) {
  const flags = finishedWork.flags;
  switch (finishedWork.tag) {
    case FunctionComponent: {
      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
      if (flags & Update) {
        commitHookLayoutEffects(finishedWork, HookLayout | HookHasEffect);
      }
      break;
    }
    case HostRoot: {
      recursivelyTraverseLayoutEffects(finishedRoot, finishedWork);
      break;
    }
    default:
      break;
  }
}
function recursivelyTraverseLayoutEffects(root, parentFiber) {
  if (parentFiber.subtreeFlags & LayoutMask) {
    let child = parentFiber.child;
    while (child !== null) {
      const current = child.alternate;
      commitLayoutEffectOnFiber(root, current, child);
      child = child.sibling;
    }
  }
}
function commitHookLayoutEffects(finishedWork, hookFlags) {
  commitHookEffectListMount(hookFlags, finishedWork);
}

42.10 ReactFiberHooks.js #

src\react-reconciler\src\ReactFiberHooks.js

import ReactSharedInternals from "shared/ReactSharedInternals";
import { enqueueConcurrentHookUpdate } from "./ReactFiberConcurrentUpdates";
import { scheduleUpdateOnFiber, requestUpdateLane, requestEventTime } from "./ReactFiberWorkLoop";
import is from "shared/objectIs";
import { Passive as PassiveEffect, Update as UpdateEffect } from "./ReactFiberFlags";
import { HasEffect as HookHasEffect, Passive as HookPassive, Layout as HookLayout } from "./ReactHookEffectTags";
import { NoLanes, NoLane, mergeLanes, isSubsetOfLanes } from './ReactFiberLane';
+import { readContext } from './ReactFiberNewContext';

const { ReactCurrentDispatcher } = ReactSharedInternals;
let currentlyRenderingFiber = null;
let workInProgressHook = null;
let currentHook = null;
let renderLanes = NoLanes;

const HooksDispatcherOnMountInDEV = {
  useReducer: mountReducer,
  useState: mountState,
  useEffect: mountEffect,
  useLayoutEffect: mountLayoutEffect,
  useRef: mountRef,
+ useContext: readContext
};
const HooksDispatcherOnUpdateInDEV = {
  useReducer: updateReducer,
  useState: updateState,
  useEffect: updateEffect,
  useLayoutEffect: updateLayoutEffect,
  useRef: updateRef,
+ useContext: readContext
};
function mountRef(initialValue) {
  const hook = mountWorkInProgressHook();
  const ref = {
    current: initialValue,
  };
  hook.memoizedState = ref;
  return ref;
}
function updateRef() {
  const hook = updateWorkInProgressHook();
  return hook.memoizedState;
}
export function useLayoutEffect(reducer, initialArg) {
  return ReactCurrentDispatcher.current.useLayoutEffect(reducer, initialArg);
}
function updateLayoutEffect(create, deps) {
  return updateEffectImpl(UpdateEffect, HookLayout, create, deps);
}
function mountLayoutEffect(create, deps) {
  const fiberFlags = UpdateEffect;
  return mountEffectImpl(fiberFlags, HookLayout, create, deps);
}
function updateEffect(create, deps) {
  return updateEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function updateEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = updateWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  let destroy;
  if (currentHook !== null) {
    const prevEffect = currentHook.memoizedState;
    destroy = prevEffect.destroy;
    if (nextDeps !== null) {
      const prevDeps = prevEffect.deps;
      if (areHookInputsEqual(nextDeps, prevDeps)) {
        hook.memoizedState = pushEffect(hookFlags, create, destroy, nextDeps);
        return;
      }
    }
  }
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, destroy, nextDeps);
}
function areHookInputsEqual(nextDeps, prevDeps) {
  if (prevDeps === null) {
    return false;
  }
  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (is(nextDeps[i], prevDeps[i])) {
      continue;
    }
    return false;
  }

  return true;
}
function mountEffect(create, deps) {
  return mountEffectImpl(PassiveEffect, HookPassive, create, deps);
}
function mountEffectImpl(fiberFlags, hookFlags, create, deps) {
  const hook = mountWorkInProgressHook();
  const nextDeps = deps === undefined ? null : deps;
  currentlyRenderingFiber.flags |= fiberFlags;
  hook.memoizedState = pushEffect(HookHasEffect | hookFlags, create, undefined, nextDeps);
}
function pushEffect(tag, create, destroy, deps) {
  const effect = {
    tag,
    create,
    destroy,
    deps,
    next: null,
  };
  let componentUpdateQueue = currentlyRenderingFiber.updateQueue;
  if (componentUpdateQueue === null) {
    componentUpdateQueue = createFunctionComponentUpdateQueue();
    currentlyRenderingFiber.updateQueue = componentUpdateQueue;
    componentUpdateQueue.lastEffect = effect.next = effect;
  } else {
    const lastEffect = componentUpdateQueue.lastEffect;
    if (lastEffect === null) {
      componentUpdateQueue.lastEffect = effect.next = effect;
    } else {
      const firstEffect = lastEffect.next;
      lastEffect.next = effect;
      effect.next = firstEffect;
      componentUpdateQueue.lastEffect = effect;
    }
  }
  return effect;
}
function createFunctionComponentUpdateQueue() {
  return {
    lastEffect: null,
  };
}
function basicStateReducer(state, action) {
  return typeof action === "function" ? action(state) : action;
}
function mountReducer(reducer, initialArg) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialArg;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: reducer,
    lastRenderedState: initialArg
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchReducerAction.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function updateReducer(reducer) {
  const hook = updateWorkInProgressHook();
  const queue = hook.queue;
  queue.lastRenderedReducer = reducer;
  const current = currentHook;
  let baseQueue = current.baseQueue;
  const pendingQueue = queue.pending;
  if (pendingQueue !== null) {
    if (baseQueue !== null) {
      const baseFirst = baseQueue.next;
      const pendingFirst = pendingQueue.next;
      baseQueue.next = pendingFirst;
      pendingQueue.next = baseFirst;
    }
    current.baseQueue = baseQueue = pendingQueue;
    queue.pending = null;
  }
  if (baseQueue !== null) {
    printQueue(baseQueue)
    const first = baseQueue.next;
    let newState = current.baseState;
    let newBaseState = null;
    let newBaseQueueFirst = null;
    let newBaseQueueLast = null;
    let update = first;
    do {
      const updateLane = update.lane;
      const shouldSkipUpdate = !isSubsetOfLanes(renderLanes, updateLane);
      if (shouldSkipUpdate) {
        const clone = {
          lane: updateLane,
          action: update.action,
          hasEagerState: update.hasEagerState,
          eagerState: update.eagerState,
          next: null,
        };
        if (newBaseQueueLast === null) {
          newBaseQueueFirst = newBaseQueueLast = clone;
          newBaseState = newState;
        } else {
          newBaseQueueLast = newBaseQueueLast.next = clone;
        }
        currentlyRenderingFiber.lanes = mergeLanes(currentlyRenderingFiber.lanes, updateLane);
      } else {
        if (newBaseQueueLast !== null) {
          const clone = {
            lane: NoLane,
            action: update.action,
            hasEagerState: update.hasEagerState,
            eagerState: update.eagerState,
            next: null,
          };
          newBaseQueueLast = newBaseQueueLast.next = clone;
        }
        if (update.hasEagerState) {
          newState = update.eagerState;
        } else {
          const action = update.action;
          newState = reducer(newState, action);
        }
      }
      update = update.next;
    } while (update !== null && update !== first);
    if (newBaseQueueLast === null) {
      newBaseState = newState;
    } else {
      newBaseQueueLast.next = newBaseQueueFirst;
    }
    hook.memoizedState = newState;
    hook.baseState = newBaseState;
    hook.baseQueue = newBaseQueueLast;
    queue.lastRenderedState = newState;
  }
  if (baseQueue === null) {
    queue.lanes = NoLanes;
  }
  const dispatch = queue.dispatch;
  return [hook.memoizedState, dispatch];
}
function mountState(initialState) {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = initialState;
  const queue = {
    pending: null,
    dispatch: null,
    lastRenderedReducer: basicStateReducer,
    lastRenderedState: initialState,
  };
  hook.queue = queue;
  const dispatch = (queue.dispatch = dispatchSetState.bind(null, currentlyRenderingFiber, queue));
  return [hook.memoizedState, dispatch];
}
function dispatchSetState(fiber, queue, action) {
  const lane = requestUpdateLane(fiber);
  const update = {
    lane,
    action,
    hasEagerState: false,
    eagerState: null,
    next: null,
  };
  const alternate = fiber.alternate;
  if (fiber.lanes === NoLanes && (alternate === null || alternate.lanes === NoLanes)) {
    const lastRenderedReducer = queue.lastRenderedReducer;
    const currentState = queue.lastRenderedState;
    const eagerState = lastRenderedReducer(currentState, action);
    update.hasEagerState = true;
    update.eagerState = eagerState;
    if (is(eagerState, currentState)) {
      return;
    }
  }
  const root = enqueueConcurrentHookUpdate(fiber, queue, update, lane);
  const eventTime = requestEventTime();
  scheduleUpdateOnFiber(root, fiber, lane, eventTime);
}
function updateState(initialState) {
  return updateReducer(basicStateReducer, initialState);
}
function mountWorkInProgressHook() {
  const hook = {
    memoizedState: null,
    queue: null,
    next: null,
    baseState: null,
    baseQueue: null,
  };
  if (workInProgressHook === null) {
    currentlyRenderingFiber.memoizedState = workInProgressHook = hook;
  } else {
    workInProgressHook = workInProgressHook.next = hook;
  }
  return workInProgressHook;
}
function dispatchReducerAction(fiber, queue, action) {
  const update = {
    action,
    next: null,
  };
  const root = enqueueConcurrentHookUpdate(fiber, queue, update);
  scheduleUpdateOnFiber(root, fiber);
}

function updateWorkInProgressHook() {
  let nextCurrentHook;
  if (currentHook === null) {
    const current = currentlyRenderingFiber.alternate;
    if (current !== null) {
      nextCurrentHook = current.memoizedState;
    } else {
      nextCurrentHook = null;
    }
  } else {
    nextCurrentHook = currentHook.next;
  }

  let nextWorkInProgressHook;
  if (workInProgressHook === null) {
    nextWorkInProgressHook = currentlyRenderingFiber.memoizedState;
  } else {
    nextWorkInProgressHook = workInProgressHook.next;
  }

  if (nextWorkInProgressHook !== null) {
    workInProgressHook = nextWorkInProgressHook;
    nextWorkInProgressHook = workInProgressHook.next;
    currentHook = nextCurrentHook;
  } else {
    currentHook = nextCurrentHook;
    const newHook = {
      memoizedState: currentHook.memoizedState,
      queue: currentHook.queue,
      next: null,
      baseState: currentHook.baseState,
      baseQueue: currentHook.baseQueue,
    };
    if (workInProgressHook === null) {
      currentlyRenderingFiber.memoizedState = workInProgressHook = newHook;
    } else {
      workInProgressHook = workInProgressHook.next = newHook;
    }
  }
  return workInProgressHook;
}

export function renderWithHooks(current, workInProgress, Component, props, nextRenderLanes) {
  renderLanes = nextRenderLanes;
  currentlyRenderingFiber = workInProgress;
  workInProgress.updateQueue = null;
  workInProgress.memoizedState = null;
  if (current !== null && current.memoizedState !== null) {
    ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;
  } else {
    ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;
  }
  const children = Component(props);
  currentlyRenderingFiber = null;
  workInProgressHook = null;
  currentHook = null;
  renderLanes = NoLanes;
  return children;
}

function printQueue(queue) {
  const first = queue.next;
  let desc = '';
  let update = first;
  do {
    desc += ("=>" + (update.action.id));
    update = update.next;
  } while (update !== null && update !== first);
  desc += "=>null";
  console.log(desc);
}

42.11 ReactFiberNewContext.js #

src\react-reconciler\src\ReactFiberNewContext.js

export function pushProvider(context, nextValue) {
  context._currentValue = nextValue;
}

export function readContext(context) {
  return context._currentValue;
}

42.12 ReactWorkTags.js #

src\react-reconciler\src\ReactWorkTags.js

export const FunctionComponent = 0;
export const IndeterminateComponent = 2;
export const HostRoot = 3;
export const HostComponent = 5;
export const HostText = 6;
+export const ContextProvider = 10;

42.13 ReactSymbols.js #

src\shared\ReactSymbols.js

export const REACT_ELEMENT_TYPE = Symbol.for("react.element");
+export const REACT_PROVIDER_TYPE = Symbol.for('react.provider');
+export const REACT_CONTEXT_TYPE = Symbol.for('react.context');
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