Untrack a boundary after it errors

If we have already added resumable slots to a boundary we need to undo that
when it errors later.

Ideally, we'd remove the whole parent path in this case. If this is the
only thing that postpones, we incorrectly think there's resumable
slots.

Author: sebmarkbage

packages/react-server/src/ReactFizzServer.js

@@ -994,6 +994,8 @@ function renderSuspenseBoundary(
     }
     encodeErrorForBoundary(newBoundary, errorDigest, error, thrownInfo);
 
+    untrackBoundary(request, newBoundary);
+
     // We don't need to decrement any task numbers because we didn't spawn any new task.
     // We don't need to schedule any task because we know the parent has written yet.
     // We do need to fallthrough to create the fallback though.
@@ -2672,6 +2674,33 @@ function trackPostpone(
   }
 }
 
+// In case a boundary errors, we need to stop tracking it because we won't
+// resume it.
+function untrackBoundary(request: Request, boundary: SuspenseBoundary) {
+  const trackedPostpones = request.trackedPostpones;
+  if (trackedPostpones === null) {
+    return;
+  }
+  const boundaryKeyPath = boundary.trackedContentKeyPath;
+  if (boundaryKeyPath === null) {
+    return;
+  }
+  const boundaryNode: void | ReplayNode =
+    trackedPostpones.workingMap.get(boundaryKeyPath);
+  if (boundaryNode === undefined) {
+    return;
+  }
+
+  // Downgrade to plain ReplayNode since we won't replay through it.
+  boundaryNode.length = 4;
+  // Remove any resumable slots.
+  boundaryNode[2] = [];
+  boundaryNode[3] = null;
+
+  // TODO: We should really just remove the boundary from all parent paths too so
+  // we don't replay the path to it.
+}
+
 function injectPostponedHole(
   request: Request,
   task: RenderTask,
@@ -3007,6 +3036,7 @@ function erroredTask(
     if (boundary.status !== CLIENT_RENDERED) {
       boundary.status = CLIENT_RENDERED;
       encodeErrorForBoundary(boundary, errorDigest, error, errorInfo);
+      untrackBoundary(request, boundary);
 
       // Regardless of what happens next, this boundary won't be displayed,
       // so we can flush it, if the parent already flushed.
@@ -3192,6 +3222,8 @@ function abortTask(task: Task, request: Request, error: mixed): void {
       }
       encodeErrorForBoundary(boundary, errorDigest, errorMessage, errorInfo);
 
+      untrackBoundary(request, boundary);
+
       if (boundary.parentFlushed) {
         request.clientRenderedBoundaries.push(boundary);
       }