Function createWorkInProgress

docs/external/js/react-dom.development.js:23828–23920

(current, pendingProps)

  } // This is used to create an alternate fiber to do work on.

  function createWorkInProgress(current, pendingProps) {
    var workInProgress = current.alternate;

    if (workInProgress === 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.
      workInProgress = createFiber(current.tag, pendingProps, current.key, current.mode);
      workInProgress.elementType = current.elementType;
      workInProgress.type = current.type;
      workInProgress.stateNode = current.stateNode;

      {
        // DEV-only fields
        {
          workInProgress._debugID = current._debugID;
        }

        workInProgress._debugSource = current._debugSource;
        workInProgress._debugOwner = current._debugOwner;
        workInProgress._debugHookTypes = current._debugHookTypes;
      }

      workInProgress.alternate = current;
      current.alternate = workInProgress;
    } else {
      workInProgress.pendingProps = pendingProps; // We already have an alternate.
      // Reset the effect tag.

      workInProgress.effectTag = NoEffect; // The effect list is no longer valid.

      workInProgress.nextEffect = null;
      workInProgress.firstEffect = null;
      workInProgress.lastEffect = null;

      {
        // We intentionally reset, rather than copy, actualDuration & actualStartTime.
        // This prevents time from endlessly accumulating in new commits.
        // This has the downside of resetting values for different priority renders,
        // But works for yielding (the common case) and should support resuming.
        workInProgress.actualDuration = 0;
        workInProgress.actualStartTime = -1;
      }
    }

    workInProgress.childExpirationTime = current.childExpirationTime;
    workInProgress.expirationTime = current.expirationTime;
    workInProgress.child = current.child;
    workInProgress.memoizedProps = current.memoizedProps;
    workInProgress.memoizedState = current.memoizedState;
    workInProgress.updateQueue = current.updateQueue; // Clone the dependencies object. This is mutated during the render phase, so
    // it cannot be shared with the current fiber.

    var currentDependencies = current.dependencies;
    workInProgress.dependencies = currentDependencies === null ? null : {
      expirationTime: currentDependencies.expirationTime,