ReactUpdateQueue.new.js

processUpdateQueue()

---

源码

export function processUpdateQueue<State>(
  workInProgress: Fiber,
  props: any,
  instance: any,
  renderLanes: Lanes,
): void {
  // This is always non-null on a ClassComponent or HostRoot
  const queue: UpdateQueue<State> = (workInProgress.updateQueue: any);

  hasForceUpdate = false;

  if (__DEV__) {
    currentlyProcessingQueue = queue.shared;
  }

  let firstBaseUpdate = queue.firstBaseUpdate;
  let lastBaseUpdate = queue.lastBaseUpdate;

  // Check if there are pending updates. If so, transfer them to the base queue.
  let pendingQueue = queue.shared.pending;
  if (pendingQueue !== null) {
    queue.shared.pending = null;

    // The pending queue is circular. Disconnect the pointer between first
    // and last so that it's non-circular.
    const lastPendingUpdate = pendingQueue;
    const firstPendingUpdate = lastPendingUpdate.next;
    lastPendingUpdate.next = null;
    // Append pending updates to base queue
    if (lastBaseUpdate === null) {
      firstBaseUpdate = firstPendingUpdate;
    } else {
      lastBaseUpdate.next = firstPendingUpdate;
    }
    lastBaseUpdate = lastPendingUpdate;

    // If there's a current queue, and it's different from the base queue, then
    // we need to transfer the updates to that queue, too. Because the base
    // queue is a singly-linked list with no cycles, we can append to both
    // lists and take advantage of structural sharing.
    // TODO: Pass `current` as argument
    const current = workInProgress.alternate;
    if (current !== null) {
      // This is always non-null on a ClassComponent or HostRoot
      const currentQueue: UpdateQueue<State> = (current.updateQueue: any);
      const currentLastBaseUpdate = currentQueue.lastBaseUpdate;
      if (currentLastBaseUpdate !== lastBaseUpdate) {
        if (currentLastBaseUpdate === null) {
          currentQueue.firstBaseUpdate = firstPendingUpdate;
        } else {
          currentLastBaseUpdate.next = firstPendingUpdate;
        }
        currentQueue.lastBaseUpdate = lastPendingUpdate;
      }
    }
  }

  // These values may change as we process the queue.
  if (firstBaseUpdate !== null) {
    // Iterate through the list of updates to compute the result.
    let newState = queue.baseState;
    // TODO: Don't need to accumulate this. Instead, we can remove renderLanes
    // from the original lanes.
    let newLanes = NoLanes;

    let newBaseState = null;
    let newFirstBaseUpdate = null;
    let newLastBaseUpdate = null;

    let update = firstBaseUpdate;
    do {
      const updateLane = update.lane;
      const updateEventTime = update.eventTime;
      if (!isSubsetOfLanes(renderLanes, updateLane)) {
        // Priority is insufficient. Skip this update. If this is the first
        // skipped update, the previous update/state is the new base
        // update/state.
        const clone: Update<State> = {
          eventTime: updateEventTime,
          lane: updateLane,

          tag: update.tag,
          payload: update.payload,
          callback: update.callback,

          next: null,
        };
        if (newLastBaseUpdate === null) {
          newFirstBaseUpdate = newLastBaseUpdate = clone;
          newBaseState = newState;
        } else {
          newLastBaseUpdate = newLastBaseUpdate.next = clone;
        }
        // Update the remaining priority in the queue.
        newLanes = mergeLanes(newLanes, updateLane);
      } else {
        // This update does have sufficient priority.

        if (newLastBaseUpdate !== null) {
          const clone: Update<State> = {
            eventTime: updateEventTime,
            // This update is going to be committed so we never want uncommit
            // it. Using NoLane works because 0 is a subset of all bitmasks, so
            // this will never be skipped by the check above.
            lane: NoLane,

            tag: update.tag,
            payload: update.payload,
            callback: update.callback,

            next: null,
          };
          newLastBaseUpdate = newLastBaseUpdate.next = clone;
        }

        // Process this update.
        newState = getStateFromUpdate(
          workInProgress,
          queue,
          update,
          newState,
          props,
          instance,
        );
        const callback = update.callback;
        if (callback !== null) {
          workInProgress.flags |= Callback;
          const effects = queue.effects;
          if (effects === null) {
            queue.effects = [update];
          } else {
            effects.push(update);
          }
        }
      }
      update = update.next;
      if (update === null) {
        pendingQueue = queue.shared.pending;
        if (pendingQueue === null) {
          break;
        } else {
          // An update was scheduled from inside a reducer. Add the new
          // pending updates to the end of the list and keep processing.
          const lastPendingUpdate = pendingQueue;
          // Intentionally unsound. Pending updates form a circular list, but we
          // unravel them when transferring them to the base queue.
          const firstPendingUpdate = ((lastPendingUpdate.next: any): Update<State>);
          lastPendingUpdate.next = null;
          update = firstPendingUpdate;
          queue.lastBaseUpdate = lastPendingUpdate;
          queue.shared.pending = null;
        }
      }
    } while (true);

    if (newLastBaseUpdate === null) {
      newBaseState = newState;
    }

    queue.baseState = ((newBaseState: any): State);
    queue.firstBaseUpdate = newFirstBaseUpdate;
    queue.lastBaseUpdate = newLastBaseUpdate;

    // Set the remaining expiration time to be whatever is remaining in the queue.
    // This should be fine because the only two other things that contribute to
    // expiration time are props and context. We're already in the middle of the
    // begin phase by the time we start processing the queue, so we've already
    // dealt with the props. Context in components that specify
    // shouldComponentUpdate is tricky; but we'll have to account for
    // that regardless.
    markSkippedUpdateLanes(newLanes);
    workInProgress.lanes = newLanes;
    workInProgress.memoizedState = newState;
  }

  if (__DEV__) {
    currentlyProcessingQueue = null;
  }
}