Function updateSuspenseComponent

dash/deps/react-dom@18.2.0.js:20279–20396

(current, workInProgress, renderLanes)

  }

  function updateSuspenseComponent(current, workInProgress, renderLanes) {
    var nextProps = workInProgress.pendingProps; // This is used by DevTools to force a boundary to suspend.

    {
      if (shouldSuspend(workInProgress)) {
        workInProgress.flags |= DidCapture;
      }
    }

    var suspenseContext = suspenseStackCursor.current;
    var showFallback = false;
    var didSuspend = (workInProgress.flags & DidCapture) !== NoFlags;

    if (didSuspend || shouldRemainOnFallback(suspenseContext, current)) {
      // Something in this boundary's subtree already suspended. Switch to
      // rendering the fallback children.
      showFallback = true;
      workInProgress.flags &= ~DidCapture;
    } else {
      // Attempting the main content
      if (current === null || current.memoizedState !== null) {
        // This is a new mount or this boundary is already showing a fallback state.
        // Mark this subtree context as having at least one invisible parent that could
        // handle the fallback state.
        // Avoided boundaries are not considered since they cannot handle preferred fallback states.
        {
          suspenseContext = addSubtreeSuspenseContext(suspenseContext, InvisibleParentSuspenseContext);
        }
      }
    }

    suspenseContext = setDefaultShallowSuspenseContext(suspenseContext);
    pushSuspenseContext(workInProgress, suspenseContext); // OK, the next part is confusing. We're about to reconcile the Suspense
    // boundary's children. This involves some custom reconciliation logic. Two
    // main reasons this is so complicated.
    //
    // First, Legacy Mode has different semantics for backwards compatibility. The
    // primary tree will commit in an inconsistent state, so when we do the
    // second pass to render the fallback, we do some exceedingly, uh, clever
    // hacks to make that not totally break. Like transferring effects and
    // deletions from hidden tree. In Concurrent Mode, it's much simpler,
    // because we bailout on the primary tree completely and leave it in its old
    // state, no effects. Same as what we do for Offscreen (except that
    // Offscreen doesn't have the first render pass).
    //
    // Second is hydration. During hydration, the Suspense fiber has a slightly
    // different layout, where the child points to a dehydrated fragment, which
    // contains the DOM rendered by the server.
    //
    // Third, even if you set all that aside, Suspense is like error boundaries in
    // that we first we try to render one tree, and if that fails, we render again
    // and switch to a different tree. Like a try/catch block. So we have to track
    // which branch we're currently rendering. Ideally we would model this using
    // a stack.

    if (current === null) {
      // Initial mount
      // Special path for hydration