[WIP] Shot-in-the-dark bugfix guess

Got a non-reproducible bug report internally. Based on the info in the
bug report, I think it might be related to this code here.

The original code is definitely wrong but I don't know if it's the same
bug that's being reported.

Pushing this so we can try it and see. Will try to write a test and
land the fix regardless.

Author: acdlite

packages/react-reconciler/src/ReactFiberWorkLoop.new.js

@@ -740,18 +740,16 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
 
   // Flush any pending passive effects before deciding which lanes to work on,
   // in case they schedule additional work.
-  const originalCallbackNode = root.callbackNode;
+  const originalCallbackPriority = root.callbackPriority;
   const didFlushPassiveEffects = flushPassiveEffects();
   if (didFlushPassiveEffects) {
     // Something in the passive effect phase may have canceled the current task.
     // Check if the task node for this root was changed.
-    if (root.callbackNode !== originalCallbackNode) {
+    if (root.callbackPriority !== originalCallbackPriority) {
       // The current task was canceled. Exit. We don't need to call
       // `ensureRootIsScheduled` because the check above implies either that
       // there's a new task, or that there's no remaining work on this root.
       return null;
-    } else {
-      // Current task was not canceled. Continue.
     }
   }
 
@@ -822,7 +820,7 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
   }
 
   ensureRootIsScheduled(root, now());
-  if (root.callbackNode === originalCallbackNode) {
+  if (root.callbackPriority === originalCallbackPriority) {
     // The task node scheduled for this root is the same one that's
     // currently executed. Need to return a continuation.
     return performConcurrentWorkOnRoot.bind(null, root);

packages/react-reconciler/src/ReactFiberWorkLoop.old.js

@@ -740,18 +740,16 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
 
   // Flush any pending passive effects before deciding which lanes to work on,
   // in case they schedule additional work.
-  const originalCallbackNode = root.callbackNode;
+  const originalCallbackPriority = root.callbackPriority;
   const didFlushPassiveEffects = flushPassiveEffects();
   if (didFlushPassiveEffects) {
     // Something in the passive effect phase may have canceled the current task.
     // Check if the task node for this root was changed.
-    if (root.callbackNode !== originalCallbackNode) {
+    if (root.callbackPriority !== originalCallbackPriority) {
       // The current task was canceled. Exit. We don't need to call
       // `ensureRootIsScheduled` because the check above implies either that
       // there's a new task, or that there's no remaining work on this root.
       return null;
-    } else {
-      // Current task was not canceled. Continue.
     }
   }
 
@@ -822,7 +820,7 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
   }
 
   ensureRootIsScheduled(root, now());
-  if (root.callbackNode === originalCallbackNode) {
+  if (root.callbackPriority === originalCallbackPriority) {
     // The task node scheduled for this root is the same one that's
     // currently executed. Need to return a continuation.
     return performConcurrentWorkOnRoot.bind(null, root);