feat(computed): 实现计算属性缓存优化和调度器支持

- 添加 _dirty 标志位控制计算属性重新执行逻辑
- 在 ReactiveEffect 构造函数中增加调度器参数支持
- 实现计算属性值变更时的依赖触发机制
- 重构 triggerEffects 函数优先处理计算属性依赖
- 新增 EffectScheduler 类型定义统一调度器类型
- 添加 computed-cache.html 示例验证缓存功能

packages/reactivity/src/computed.ts

@@ -1,20 +1,30 @@
 import { isFunction } from '@vue/shared'
 import { Dep } from './dep'
 import { ReactiveEffect } from './effect'
-import { trackRefValue } from './ref'
+import { trackRefValue, triggerRefValue } from './ref'
 
 export class ComputedRefImpl<T> {
   public dep?: Dep = undefined
   private _value!: T
   public readonly effect: ReactiveEffect<T>
   public readonly __v_isRef = true
+
+  public _dirty = true //为true时,需要重新执行run方法, 也就是说数据脏了的意思
   constructor(getter) {
-    this.effect = new ReactiveEffect(getter)
+    this.effect = new ReactiveEffect(getter, () => {
+      if (!this._dirty) {
+        this._dirty = true
+        triggerRefValue(this)
+      }
+    })
     this.effect.computed = this
   }
   get value() {
-    trackRefValue(this) //触发依赖
-    this._value = this.effect.run()
+    trackRefValue(this)
+    if (this._dirty) {
+      this._dirty = false
+      this._value = this.effect.run()
+    }
     return this._value
   }
 }

packages/reactivity/src/effect.ts

@@ -1,6 +1,7 @@
 import { createDep, Dep } from './dep'
 import { isArray } from '@vue/shared'
 import { ComputedRefImpl } from './computed'
+export type EffectScheduler = (...args: any[]) => any
 
 type KeyToDepMap = Map<any, Dep>
 /**
@@ -21,7 +22,10 @@ export let activeEffect: ReactiveEffect | undefined
 
 export class ReactiveEffect<T = any> {
   computed?: ComputedRefImpl<T>
-  constructor(public fn: () => T) {}
+  constructor(
+    public fn: () => T,
+    public scheduler: EffectScheduler | null = null
+  ) {}
   run() {
     //当前被激活的effect实例
     activeEffect = this
@@ -78,14 +82,26 @@ export function trigger(target: object, key: unknown, newValue: unknown) {
 }
 
 /**
- * 依次触发dep中保存的依赖
+ * 触发dep中保存的依赖
  * @param dep
  */
 export function triggerEffects(dep: Dep) {
+  //把dep构建为一个数组
   const effects = isArray(dep) ? dep : [...dep]
-  //依次触发依赖
+  //不再依次触发依赖
+  // for (const effect of effects) {
+  //     triggerEffect(effect)
+  // }
+  //而是先触发所有的计算属性依赖, 再触发所有的非计算属性依赖
   for (const effect of effects) {
-    triggerEffect(effect)
+    if (effect.computed) {
+      triggerEffect(effect)
+    }
+  }
+  for (const effect of effects) {
+    if (!effect.computed) {
+      triggerEffect(effect)
+    }
   }
 }
 
@@ -94,5 +110,9 @@ export function triggerEffects(dep: Dep) {
  * @param effect
  */
 export function triggerEffect(effect: ReactiveEffect) {
-  effect.run()
+  if (effect.scheduler) {
+    effect.scheduler()
+  } else {
+    effect.run()
+  }
 }