Add back skipUnmountedBoundaries flag only for www

There are a few internal tests that still need to be updated, so I'm
adding this flag back for www only.

The desired behavior rolled out to 10% public, so we're confident there
are no issues.

The open source behavior remains (skipUnmountedBoundaries = true).

packages/react-dom/src/__tests__/ReactErrorBoundaries-test.internal.js

@@ -42,6 +42,7 @@ describe('ReactErrorBoundaries', () => {
     PropTypes = require('prop-types');
     ReactFeatureFlags = require('shared/ReactFeatureFlags');
     ReactFeatureFlags.replayFailedUnitOfWorkWithInvokeGuardedCallback = false;
+    ReactFeatureFlags.skipUnmountedBoundaries = true;
     ReactDOM = require('react-dom');
     React = require('react');
     act = require('jest-react').act;

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

@@ -35,6 +35,7 @@ import {
   enableSchedulingProfiler,
   disableSchedulerTimeoutInWorkLoop,
   enableStrictEffects,
+  skipUnmountedBoundaries,
   enableUpdaterTracking,
   enableCache,
   enableTransitionTracing,
@@ -2537,7 +2538,13 @@ export function captureCommitPhaseError(
     return;
   }
 
-  let fiber = nearestMountedAncestor;
+  let fiber = null;
+  if (skipUnmountedBoundaries) {
+    fiber = nearestMountedAncestor;
+  } else {
+    fiber = sourceFiber.return;
+  }
+
   while (fiber !== null) {
     if (fiber.tag === HostRoot) {
       captureCommitPhaseErrorOnRoot(fiber, sourceFiber, error);
@@ -2570,9 +2577,14 @@ export function captureCommitPhaseError(
   }
 
   if (__DEV__) {
+    // TODO: Until we re-land skipUnmountedBoundaries (see #20147), this warning
+    // will fire for errors that are thrown by destroy functions inside deleted
+    // trees. What it should instead do is propagate the error to the parent of
+    // the deleted tree. In the meantime, do not add this warning to the
+    // allowlist; this is only for our internal use.
     console.error(
       'Internal React error: Attempted to capture a commit phase error ' +
-        'inside a detached tree. This indicates a bug in React. Potential ' +
+        'inside a detached tree. This indicates a bug in React. Likely ' +
         'causes include deleting the same fiber more than once, committing an ' +
         'already-finished tree, or an inconsistent return pointer.\n\n' +
         'Error message:\n\n%s',

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

@@ -35,6 +35,7 @@ import {
   enableSchedulingProfiler,
   disableSchedulerTimeoutInWorkLoop,
   enableStrictEffects,
+  skipUnmountedBoundaries,
   enableUpdaterTracking,
   enableCache,
   enableTransitionTracing,
@@ -2537,7 +2538,13 @@ export function captureCommitPhaseError(
     return;
   }
 
-  let fiber = nearestMountedAncestor;
+  let fiber = null;
+  if (skipUnmountedBoundaries) {
+    fiber = nearestMountedAncestor;
+  } else {
+    fiber = sourceFiber.return;
+  }
+
   while (fiber !== null) {
     if (fiber.tag === HostRoot) {
       captureCommitPhaseErrorOnRoot(fiber, sourceFiber, error);
@@ -2570,9 +2577,14 @@ export function captureCommitPhaseError(
   }
 
   if (__DEV__) {
+    // TODO: Until we re-land skipUnmountedBoundaries (see #20147), this warning
+    // will fire for errors that are thrown by destroy functions inside deleted
+    // trees. What it should instead do is propagate the error to the parent of
+    // the deleted tree. In the meantime, do not add this warning to the
+    // allowlist; this is only for our internal use.
     console.error(
       'Internal React error: Attempted to capture a commit phase error ' +
-        'inside a detached tree. This indicates a bug in React. Potential ' +
+        'inside a detached tree. This indicates a bug in React. Likely ' +
         'causes include deleting the same fiber more than once, committing an ' +
         'already-finished tree, or an inconsistent return pointer.\n\n' +
         'Error message:\n\n%s',

packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.js

@@ -2351,6 +2351,7 @@ describe('ReactHooksWithNoopRenderer', () => {
         };
       });
 
+      // @gate skipUnmountedBoundaries
       it('should use the nearest still-mounted boundary if there are no unmounted boundaries', () => {
         act(() => {
           ReactNoop.render(
@@ -2376,6 +2377,7 @@ describe('ReactHooksWithNoopRenderer', () => {
         ]);
       });
 
+      // @gate skipUnmountedBoundaries
       it('should skip unmounted boundaries and use the nearest still-mounted boundary', () => {
         function Conditional({showChildren}) {
           if (showChildren) {
@@ -2418,6 +2420,7 @@ describe('ReactHooksWithNoopRenderer', () => {
         ]);
       });
 
+      // @gate skipUnmountedBoundaries
       it('should call getDerivedStateFromError in the nearest still-mounted boundary', () => {
         function Conditional({showChildren}) {
           if (showChildren) {
@@ -2461,6 +2464,7 @@ describe('ReactHooksWithNoopRenderer', () => {
         ]);
       });
 
+      // @gate skipUnmountedBoundaries
       it('should rethrow error if there are no still-mounted boundaries', () => {
         function Conditional({showChildren}) {
           if (showChildren) {
@@ -3186,6 +3190,7 @@ describe('ReactHooksWithNoopRenderer', () => {
       ]);
     });
 
+    // @gate skipUnmountedBoundaries
     it('catches errors thrown in useLayoutEffect', () => {
       class ErrorBoundary extends React.Component {
         state = {error: null};

packages/react-reconciler/src/__tests__/ReactIncrementalErrorHandling-test.internal.js

@@ -1017,6 +1017,7 @@ describe('ReactIncrementalErrorHandling', () => {
     expect(Scheduler).toFlushAndYield(['Foo']);
   });
 
+  // @gate skipUnmountedBoundaries
   it('should not attempt to recover an unmounting error boundary', () => {
     class Parent extends React.Component {
       componentWillUnmount() {

packages/shared/ReactFeatureFlags.js

@@ -28,6 +28,10 @@ export const enablePersistentOffscreenHostContainer = false;
 // like migrating internal callers or performance testing.
 // -----------------------------------------------------------------------------
 
+// This rolled out to 10% public in www, so we should be able to land, but some
+// internal tests need to be updated. The open source behavior is correct.
+export const skipUnmountedBoundaries = true;
+
 // Destroy layout effects for components that are hidden because something
 // suspended in an update and recreate them when they are shown again (after the
 // suspended boundary has resolved). Note that this should be an uncommon use

packages/shared/forks/ReactFeatureFlags.native-fb.js

@@ -56,6 +56,7 @@ export const enableComponentStackLocations = false;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = true;

packages/shared/forks/ReactFeatureFlags.native-oss.js

@@ -47,6 +47,7 @@ export const enableComponentStackLocations = false;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.test-renderer.js

@@ -47,6 +47,7 @@ export const enableComponentStackLocations = true;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.test-renderer.native.js

@@ -43,6 +43,7 @@ export const enableComponentStackLocations = false;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -47,6 +47,7 @@ export const enableComponentStackLocations = true;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.testing.js

@@ -47,6 +47,7 @@ export const enableComponentStackLocations = true;
 export const enableLegacyFBSupport = false;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = false;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.testing.www.js

@@ -47,6 +47,7 @@ export const enableComponentStackLocations = true;
 export const enableLegacyFBSupport = !__EXPERIMENTAL__;
 export const enableFilterEmptyStringAttributesDOM = false;
 export const disableNativeComponentFrames = false;
+export const skipUnmountedBoundaries = true;
 export const deletedTreeCleanUpLevel = 3;
 export const enableSuspenseLayoutEffectSemantics = false;
 export const enableGetInspectorDataForInstanceInProduction = false;

packages/shared/forks/ReactFeatureFlags.www-dynamic.js

@@ -17,6 +17,7 @@ export const warnAboutSpreadingKeyToJSX = __VARIANT__;
 export const disableInputAttributeSyncing = __VARIANT__;
 export const enableFilterEmptyStringAttributesDOM = __VARIANT__;
 export const enableLegacyFBSupport = __VARIANT__;
+export const skipUnmountedBoundaries = __VARIANT__;
 export const enableUseRefAccessWarning = __VARIANT__;
 export const deletedTreeCleanUpLevel = __VARIANT__ ? 3 : 1;
 export const enableProfilerNestedUpdateScheduledHook = __VARIANT__;

packages/shared/forks/ReactFeatureFlags.www.js

@@ -24,6 +24,7 @@ export const {
   enableLegacyFBSupport,
   deferRenderPhaseUpdateToNextBatch,
   enableDebugTracing,
+  skipUnmountedBoundaries,
   createRootStrictEffectsByDefault,
   enableUseRefAccessWarning,
   disableNativeComponentFrames,