const scope = effectScope()
scope.run(() => {
  const doubled = computed(() => counter.value * 2)
  watch(doubled, () => console.log(doubled.value))
  watchEffect(() => console.log('Count: ', doubled.value))
})
// 處理掉當(dāng)前作用域內(nèi)的所有 effect
scope.stop()

// packages/reactivity/src/effectScope.ts
export function effectScope(detached?: boolean) {
  // 返回EffectScope實例
  return new EffectScope(detached)
}

export class EffectScope {
  /**
   * @internal
   */
  private _active = true
  /**
   * @internal
   */
  effects: ReactiveEffect[] = []
  /**
   * @internal
   */
  cleanups: (() => void)[] = []
  /**
   * only assigned by undetached scope
   * @internal
   */
  parent: EffectScope | undefined
  /**
   * record undetached scopes
   * @internal
   */
  scopes: EffectScope[] | undefined
  /**
   * track a child scope's index in its parent's scopes array for optimized
   * // index作用：在父作用域數(shù)組中跟蹤子作用域范圍索引以進行優(yōu)化。
   * removal
   * @internal
   */
  private index: number | undefined
  constructor(public detached = false) {
    // 記錄當(dāng)前scope為parent scope
    this.parent = activeEffectScope
    if (!detached && activeEffectScope) {
      this.index =
        (activeEffectScope.scopes || (activeEffectScope.scopes = [])).push(
          this
        ) - 1
    }
  }
  get active() {
    return this._active
  }
  run<T>(fn: () => T): T | undefined {
    if (this._active) {
      const currentEffectScope = activeEffectScope
      try {
        activeEffectScope = this
        return fn()
      } finally {
        activeEffectScope = currentEffectScope
      }
    } else if (__DEV__) {
      warn(`cannot run an inactive effect scope.`)
    }
  }
  /**
   * This should only be called on non-detached scopes
   * 必須在非分離的作用域上調(diào)用
   * @internal
   */
  on() {
    activeEffectScope = this
  }
  /**
   * This should only be called on non-detached scopes
   * @internal
   */
  off() {
    activeEffectScope = this.parent
  }
  // stop方法
  stop(fromParent?: boolean) {
    if (this._active) {
      let i, l
      // stop effects
      for (i = 0, l = this.effects.length; i < l; i++) {
        this.effects[i].stop()
      }
      // 執(zhí)行所有的cleanups
      for (i = 0, l = this.cleanups.length; i < l; i++) {
        this.cleanups[i]()
      }
      // 遞歸停止所有的子作用域
      if (this.scopes) {
        for (i = 0, l = this.scopes.length; i < l; i++) {
          this.scopes[i].stop(true)
        }
      }
      // nested scope, dereference from parent to avoid memory leaks
      if (!this.detached && this.parent && !fromParent) {
        // optimized O(1) removal
        const last = this.parent.scopes!.pop()
        if (last && last !== this) {
          this.parent.scopes![this.index!] = last
          last.index = this.index!
        }
      }
      this.parent = undefined
      this._active = false
    }
  }
}

// ReactiveEffect的構(gòu)造函數(shù)
constructor(
  public fn: () => T,
  public scheduler: EffectScheduler | null = null,
  scope?: EffectScope
) {
  // effect實例默認會被記錄到指定scope中
  // 如果沒有指定scope則會記錄到全局activeEffectScope中
  recordEffectScope(this, scope)
}
// recordEffectScope實現(xiàn)
export function recordEffectScope(
  effect: ReactiveEffect,
  // scope默認值為activeEffectScope
  scope: EffectScope | undefined = activeEffectScope
) {
  if (scope && scope.active) {
    scope.effects.push(effect)
  }
}

const instance: ComponentInternalInstance = {
  ...
  // 初始化scope
  scope: new EffectScope(true /* detached */),
  ...
}

function setupStatefulComponent(
  instance: ComponentInternalInstance,
  isSSR: boolean
) {
  // 組件對象
  const Component = instance.type as ComponentOptions
  ...
  // 2. call setup()
  const { setup } = Component
  if (setup) {
    // 創(chuàng)建setupContext
    const setupContext = (instance.setupContext =
      // setup參數(shù)個數(shù)判斷 大于一個參數(shù)創(chuàng)建setupContext
      setup.length > 1 ? createSetupContext(instance) : null)
    // instance賦值給currentInstance
    // 設(shè)置當(dāng)前實例為instance 為了在setup中可以通過getCurrentInstance獲取到當(dāng)前實例
    // 同時開啟instance.scope.on()
    setCurrentInstance(instance)
    // 暫停tracking 暫停收集副作用函數(shù)
    pauseTracking()
    // 執(zhí)行setup
    const setupResult = callWithErrorHandling(
      setup,
      instance,
      ErrorCodes.SETUP_FUNCTION,
      // setup參數(shù)
      [__DEV__ ? shallowReadonly(instance.props) : instance.props, setupContext]
    )
    // 重新開啟副作用收集
    resetTracking()
    // currentInstance置為空 
    // activeEffectScope賦值為instance.scope.parent
    // 同時instance.scope.off()
    unsetCurrentInstance()
    ...
  } else {
    finishComponentSetup(instance, isSSR)
  }
}

// support for 2.x options
if (__FEATURE_OPTIONS_API__ && !(__COMPAT__ && skipOptions)) {
  setCurrentInstance(instance)
  pauseTracking()
  // 處理options API
  applyOptions(instance)
  resetTracking()
  unsetCurrentInstance()
}

// packages/runtime-core/src/renderer.ts
const unmountComponent = (
  instance: ComponentInternalInstance,
  parentSuspense: SuspenseBoundary | null,
  doRemove?: boolean
) => {
  if (__DEV__ && instance.type.__hmrId) {
    unregisterHMR(instance)
  }
  const { bum, scope, update, subTree, um } = instance
  ...
  // stop effects in component scope
  // 副作用清除
  scope.stop()
  ...
}