function commitBeforeMutationLifecycles() {
  while (nextEffect !== null) {
    const effectTag = nextEffect.effectTag;
    // 如果有Snapshot的tag，就执行commitBeforeMutationLifeCycles
    // 对于class组件，执行getSnapshotBeforeUpdate
    if (effectTag & Snapshot) {
      const current = nextEffect.alternate;
      commitBeforeMutationLifeCycles(current, nextEffect);
    }

    nextEffect = nextEffect.nextEffect;
  }
}

if (typeof instance.getSnapshotBeforeUpdate === 'function') {
  if (
    oldProps !== current.memoizedProps ||
    oldState !== current.memoizedState
  ) {
    workInProgress.effectTag |= Snapshot;
  }
}

function commitBeforeMutationLifeCycles(
  current: Fiber | null,
  finishedWork: Fiber,
): void {
  switch (finishedWork.tag) {
    case SimpleMemoComponent: {
      // 传入的tag UnmountSnapshot NoHookEffect
      // useEffect 和 useLayoutEffect 没有使用这两个tag
      // 所以在这个阶段， useEffect 和 useLayoutEffect 都不会被调用
      // 实测了一下 SimpleMemoComponent 就是使用React.memo包裹的组件
      // 目前好像走不到这个逻辑
      commitHookEffectList(UnmountSnapshot, NoHookEffect, finishedWork);
      return;
    }
    case ClassComponent: {
      if (finishedWork.effectTag & Snapshot) {
        if (current !== null) {
          const prevProps = current.memoizedProps;
          const prevState = current.memoizedState;
          const instance = finishedWork.stateNode;
          const snapshot = instance.getSnapshotBeforeUpdate(
            finishedWork.elementType === finishedWork.type
              ? prevProps
              : resolveDefaultProps(finishedWork.type, prevProps),
            prevState,
          );
          // 将getSnapshotBeforeUpdate的返回值存储在当前实例上面，
          // 在componentDidUpdate的时候取出来，作为第三个参数传入
          instance.__reactInternalSnapshotBeforeUpdate = snapshot;
          stopPhaseTimer();
        }
      }
      return;
    }
  }
}