mountSuspenseFallbackChildren() — react Function Reference

Source Code

packages/react-reconciler/src/ReactFiberBeginWork.js lines 2631–2694

function mountSuspenseFallbackChildren(
  workInProgress: Fiber,
  primaryChildren: $FlowFixMe,
  fallbackChildren: $FlowFixMe,
  renderLanes: Lanes,
) {
  const mode = workInProgress.mode;
  const progressedPrimaryFragment: Fiber | null = workInProgress.child;

  const primaryChildProps: OffscreenProps = {
    mode: 'hidden',
    children: primaryChildren,
  };

  let primaryChildFragment;
  let fallbackChildFragment;
  if (
    !disableLegacyMode &&
    (mode & ConcurrentMode) === NoMode &&
    progressedPrimaryFragment !== null
  ) {
    // In legacy mode, we commit the primary tree as if it successfully
    // completed, even though it's in an inconsistent state.
    primaryChildFragment = progressedPrimaryFragment;
    primaryChildFragment.childLanes = NoLanes;
    primaryChildFragment.pendingProps = primaryChildProps;

    if (enableProfilerTimer && workInProgress.mode & ProfileMode) {
      // Reset the durations from the first pass so they aren't included in the
      // final amounts. This seems counterintuitive, since we're intentionally
      // not measuring part of the render phase, but this makes it match what we
      // do in Concurrent Mode.
      primaryChildFragment.actualDuration = -0;
      primaryChildFragment.actualStartTime = -1.1;
      primaryChildFragment.selfBaseDuration = -0;
      primaryChildFragment.treeBaseDuration = -0;
    }

    fallbackChildFragment = createFiberFromFragment(
      fallbackChildren,
      mode,
      renderLanes,
      null,
    );
  } else {
    primaryChildFragment = mountWorkInProgressOffscreenFiber(
      primaryChildProps,
      mode,
      NoLanes,
    );
    fallbackChildFragment = createFiberFromFragment(
      fallbackChildren,
      mode,
      renderLanes,
      null,
    );
  }

  primaryChildFragment.return = workInProgress;
  fallbackChildFragment.return = workInProgress;
  primaryChildFragment.sibling = fallbackChildFragment;
  workInProgress.child = primaryChildFragment;
  return fallbackChildFragment;
}