Repository: facebook/react
Pull request: Check for infinite update loops even if unmounted

The infinite update loop check doesn't need to run if the component already unmounted, because an update to an unmounted component can't cause a re-render. But because we used to run the check in this case, anyway, I found one test in www that happens to "rely on" this behavior (accidentally). The test is a pretty messy snapshot thing that I have no interest fixing so to unblock the sync I'm just going to switch this back to how it was.

Changed files:
filename: packages/react-reconciler/src/ReactFiberConcurrentUpdates.new.js
patch: @@ -19,7 +19,10 @@ import type {
 import type {Lane, Lanes} from './ReactFiberLane.new';
 import type {OffscreenInstance} from './ReactFiberOffscreenComponent';
 
-import {warnAboutUpdateOnNotYetMountedFiberInDEV} from './ReactFiberWorkLoop.new';
+import {
+  warnAboutUpdateOnNotYetMountedFiberInDEV,
+  throwIfInfiniteUpdateLoopDetected,
+} from './ReactFiberWorkLoop.new';
 import {
   NoLane,
   NoLanes,
@@ -207,6 +210,13 @@ function markUpdateLaneFromFiberToRoot(
 }
 
 function getRootForUpdatedFiber(sourceFiber: Fiber): FiberRoot | null {
+  // TODO: We will detect and infinite update loop and throw even if this fiber
+  // has already unmounted. This isn't really necessary but it happens to be the
+  // current behavior we've used for several release cycles. Consider not
+  // performing this check if the updated fiber already unmounted, since it's
+  // not possible for that to cause an infinite update loop.
+  throwIfInfiniteUpdateLoopDetected();
+
   // When a setState happens, we must ensure the root is scheduled. Because
   // update queues do not have a backpointer to the root, the only way to do
   // this currently is to walk up the return path. This used to not be a big

filename: packages/react-reconciler/src/ReactFiberConcurrentUpdates.old.js
patch: @@ -18,7 +18,10 @@ import type {
 } from './ReactFiberClassUpdateQueue.old';
 import type {Lane} from './ReactFiberLane.old';
 
-import {warnAboutUpdateOnNotYetMountedFiberInDEV} from './ReactFiberWorkLoop.old';
+import {
+  warnAboutUpdateOnNotYetMountedFiberInDEV,
+  throwIfInfiniteUpdateLoopDetected,
+} from './ReactFiberWorkLoop.old';
 import {mergeLanes} from './ReactFiberLane.old';
 import {NoFlags, Placement, Hydrating} from './ReactFiberFlags';
 import {HostRoot} from './ReactWorkTags';
@@ -143,6 +146,13 @@ function markUpdateLaneFromFiberToRoot(
   sourceFiber: Fiber,
   lane: Lane,
 ): FiberRoot | null {
+  // TODO: We will detect and infinite update loop and throw even if this fiber
+  // has already unmounted. This isn't really necessary but it happens to be the
+  // current behavior we've used for several release cycles. Consider not
+  // performing this check if the updated fiber already unmounted, since it's
+  // not possible for that to cause an infinite update loop.
+  throwIfInfiniteUpdateLoopDetected();
+
   // Update the source fiber's lanes
   sourceFiber.lanes = mergeLanes(sourceFiber.lanes, lane);
   let alternate = sourceFiber.alternate;

filename: packages/react-reconciler/src/ReactFiberWorkLoop.new.js
patch: @@ -536,8 +536,6 @@ export function scheduleUpdateOnFiber(
   lane: Lane,
   eventTime: number,
 ) {
-  checkForNestedUpdates();
-
   if (__DEV__) {
     if (isRunningInsertionEffect) {
       console.error('useInsertionEffect must not schedule updates.');
@@ -2782,10 +2780,12 @@ function jnd(timeElapsed: number) {
     : ceil(timeElapsed / 1960) * 1960;
 }
 
-function checkForNestedUpdates() {
+export function throwIfInfiniteUpdateLoopDetected() {
   if (nestedUpdateCount > NESTED_UPDATE_LIMIT) {
     nestedUpdateCount = 0;
+    nestedPassiveUpdateCount = 0;
     rootWithNestedUpdates = null;
+    rootWithPassiveNestedUpdates = null;
 
     throw new Error(
       'Maximum update depth exceeded. This can happen when a component ' +

filename: packages/react-reconciler/src/ReactFiberWorkLoop.old.js
patch: @@ -531,8 +531,6 @@ export function scheduleUpdateOnFiber(
   lane: Lane,
   eventTime: number,
 ) {
-  checkForNestedUpdates();
-
   if (__DEV__) {
     if (isRunningInsertionEffect) {
       console.error('useInsertionEffect must not schedule updates.');
@@ -2771,7 +2769,7 @@ function jnd(timeElapsed: number) {
     : ceil(timeElapsed / 1960) * 1960;
 }
 
-function checkForNestedUpdates() {
+export function throwIfInfiniteUpdateLoopDetected() {
   if (nestedUpdateCount > NESTED_UPDATE_LIMIT) {
     nestedUpdateCount = 0;
     rootWithNestedUpdates = null;

filename: scripts/merge-fork/forked-revisions
patch: @@ -1,2 +1,3 @@
+58bb11764bf0bb6db47527a64f693f67cdd3b0bb [FORKED] Check for infinite update loops even if unmounted
 31882b5dd66f34f70d341ea2781cacbe802bf4d5 [FORKED] Bugfix: Revealing a hidden update
 17691acc071d56261d43c3cf183f287d983baa9b [FORKED] Don't update childLanes until after current render