Unify ReactFiberCurrentOwner and ReactCurrentFiber (#29038)

We previously had two slightly different concepts for "current fiber".

There's the "owner" which is set inside of class components in prod if
string refs are enabled, and sometimes inside function components in DEV
but not other contexts.

Then we have the "current fiber" which is only set in DEV for various
warnings but is enabled in a bunch of contexts.

This unifies them into a single "current fiber".

The concept of string refs shouldn't really exist so this should really
be a DEV only concept. In the meantime, this sets the current fiber
inside class render only in prod, however, in DEV it's now enabled in
more contexts which can affect the string refs. That was already the
case that a string ref in a Function component was only connecting to
the owner in prod. Any string ref associated with any non-class won't
work regardless so that's not an issue. The practical change here is
that an element with a string ref created inside a life-cycle associated
with a class will work in DEV but not in prod. Since we need the current
fiber to be available in more contexts in DEV for the debugging
purposes. That wouldn't affect any old code since it would have a broken
ref anyway. New code shouldn't use string refs anyway.

The other implication is that "owner" doesn't necessarily mean
"rendering" since we need the "owner" to track other debug information
like stacks - in other contexts like useEffect, life cycles, etc.
Internally we have a separate `isRendering` flag that actually means
we're rendering but even that is a very overloaded concept. So anything
that uses "owner" to imply rendering might be wrong with this change.

This is a first step to a larger refactor for tracking current rendering
information.

---------

Co-authored-by: Sebastian Silbermann <silbermann.sebastian@gmail.com>

packages/react-devtools-shared/src/__tests__/treeContext-test.js

@@ -2586,14 +2586,14 @@ describe('TreeListContext', () => {
         utils.act(() => TestRenderer.create(<Contexts />));
 
         expect(store).toMatchInlineSnapshot(`
-          ✕ 2, ⚠ 0
+          ✕ 1, ⚠ 0
           [root]
               <ErrorBoundary> ✕
         `);
 
         selectNextErrorOrWarning();
         expect(state).toMatchInlineSnapshot(`
-          ✕ 2, ⚠ 0
+          ✕ 1, ⚠ 0
           [root]
           →    <ErrorBoundary> ✕
         `);
@@ -2648,14 +2648,14 @@ describe('TreeListContext', () => {
         utils.act(() => TestRenderer.create(<Contexts />));
 
         expect(store).toMatchInlineSnapshot(`
-          ✕ 2, ⚠ 0
+          ✕ 1, ⚠ 0
           [root]
               <ErrorBoundary> ✕
         `);
 
         selectNextErrorOrWarning();
         expect(state).toMatchInlineSnapshot(`
-          ✕ 2, ⚠ 0
+          ✕ 1, ⚠ 0
           [root]
           →    <ErrorBoundary> ✕
         `);
@@ -2705,7 +2705,7 @@ describe('TreeListContext', () => {
         utils.act(() => TestRenderer.create(<Contexts />));
 
         expect(store).toMatchInlineSnapshot(`
-          ✕ 3, ⚠ 0
+          ✕ 2, ⚠ 0
           [root]
             ▾ <ErrorBoundary> ✕
                 <Child> ✕
@@ -2713,7 +2713,7 @@ describe('TreeListContext', () => {
 
         selectNextErrorOrWarning();
         expect(state).toMatchInlineSnapshot(`
-          ✕ 3, ⚠ 0
+          ✕ 2, ⚠ 0
           [root]
           →  ▾ <ErrorBoundary> ✕
                  <Child> ✕

packages/react-dom/src/__tests__/refs-test.js

@@ -499,8 +499,8 @@ describe('creating element with string ref in constructor', () => {
     }
   }
 
-  // @gate !disableStringRefs
-  it('throws an error', async () => {
+  // @gate !disableStringRefs && !__DEV__
+  it('throws an error in prod', async () => {
     await expect(async function () {
       const container = document.createElement('div');
       const root = ReactDOMClient.createRoot(container);

packages/react-dom/src/client/ReactDOMRootFB.js

@@ -61,7 +61,10 @@ import {LegacyRoot} from 'react-reconciler/src/ReactRootTags';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import {has as hasInstance} from 'shared/ReactInstanceMap';
 
-import {currentOwner} from 'react-reconciler/src/ReactFiberCurrentOwner';
+import {
+  current as currentOwner,
+  isRendering,
+} from 'react-reconciler/src/ReactCurrentFiber';
 
 import assign from 'shared/assign';
 
@@ -343,7 +346,7 @@ export function findDOMNode(
 ): null | Element | Text {
   if (__DEV__) {
     const owner = currentOwner;
-    if (owner !== null && owner.stateNode !== null) {
+    if (owner !== null && isRendering && owner.stateNode !== null) {
       const warnedAboutRefsInRender = owner.stateNode._warnedAboutRefsInRender;
       if (!warnedAboutRefsInRender) {
         console.error(

packages/react-native-renderer/src/ReactNativePublicCompat.js

@@ -25,14 +25,17 @@ import {
 } from 'react-reconciler/src/ReactFiberReconciler';
 import {doesFiberContain} from 'react-reconciler/src/ReactFiberTreeReflection';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
-import {currentOwner} from 'react-reconciler/src/ReactFiberCurrentOwner';
+import {
+  current as currentOwner,
+  isRendering,
+} from 'react-reconciler/src/ReactCurrentFiber';
 
 export function findHostInstance_DEPRECATED<TElementType: ElementType>(
   componentOrHandle: ?(ElementRef<TElementType> | number),
 ): ?ElementRef<HostComponent<mixed>> {
   if (__DEV__) {
     const owner = currentOwner;
-    if (owner !== null && owner.stateNode !== null) {
+    if (owner !== null && isRendering && owner.stateNode !== null) {
       if (!owner.stateNode._warnedAboutRefsInRender) {
         console.error(
           '%s is accessing findNodeHandle inside its render(). ' +

packages/react-reconciler/src/ReactCurrentFiber.js

@@ -41,21 +41,33 @@ function getCurrentFiberStackInDev(): string {
   return '';
 }
 
+export function resetCurrentDebugFiberInDEV() {
+  if (__DEV__) {
+    resetCurrentFiber();
+  }
+}
+
+export function setCurrentDebugFiberInDEV(fiber: Fiber | null) {
+  if (__DEV__) {
+    setCurrentFiber(fiber);
+  }
+}
+
 export function resetCurrentFiber() {
   if (__DEV__) {
     ReactSharedInternals.getCurrentStack = null;
-    current = null;
     isRendering = false;
   }
+  current = null;
 }
 
 export function setCurrentFiber(fiber: Fiber | null) {
   if (__DEV__) {
     ReactSharedInternals.getCurrentStack =
       fiber === null ? null : getCurrentFiberStackInDev;
-    current = fiber;
     isRendering = false;
   }
+  current = fiber;
 }
 
 export function getCurrentFiber(): Fiber | null {

packages/react-reconciler/src/ReactFiberAsyncDispatcher.js

@@ -16,7 +16,7 @@ import {CacheContext} from './ReactFiberCacheComponent';
 
 import {disableStringRefs} from 'shared/ReactFeatureFlags';
 
-import {currentOwner} from './ReactFiberCurrentOwner';
+import {current as currentOwner} from './ReactCurrentFiber';
 
 function getCacheForType<T>(resourceType: () => T): T {
   if (!enableCache) {

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -125,6 +125,7 @@ import {
 import {
   getCurrentFiberOwnerNameInDevOrNull,
   setIsRendering,
+  setCurrentFiber,
 } from './ReactCurrentFiber';
 import {
   resolveFunctionForHotReloading,
@@ -296,7 +297,6 @@ import {
   pushRootMarkerInstance,
   TransitionTracingMarker,
 } from './ReactFiberTracingMarkerComponent';
-import {setCurrentOwner} from './ReactFiberCurrentOwner';
 
 // A special exception that's used to unwind the stack when an update flows
 // into a dehydrated boundary.
@@ -432,7 +432,6 @@ function updateForwardRef(
     markComponentRenderStarted(workInProgress);
   }
   if (__DEV__) {
-    setCurrentOwner(workInProgress);
     setIsRendering(true);
     nextChildren = renderWithHooks(
       current,
@@ -1150,7 +1149,6 @@ function updateFunctionComponent(
     markComponentRenderStarted(workInProgress);
   }
   if (__DEV__) {
-    setCurrentOwner(workInProgress);
     setIsRendering(true);
     nextChildren = renderWithHooks(
       current,
@@ -1373,7 +1371,7 @@ function finishClassComponent(
 
   // Rerender
   if (__DEV__ || !disableStringRefs) {
-    setCurrentOwner(workInProgress);
+    setCurrentFiber(workInProgress);
   }
   let nextChildren;
   if (
@@ -3419,7 +3417,6 @@ function updateContextConsumer(
   }
   let newChildren;
   if (__DEV__) {
-    setCurrentOwner(workInProgress);
     setIsRendering(true);
     newChildren = render(newValue);
     setIsRendering(false);

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -101,8 +101,8 @@ import {
 } from './ReactFiberFlags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import {
-  resetCurrentFiber as resetCurrentDebugFiberInDEV,
-  setCurrentFiber as setCurrentDebugFiberInDEV,
+  resetCurrentDebugFiberInDEV,
+  setCurrentDebugFiberInDEV,
   getCurrentFiber as getCurrentDebugFiberInDEV,
 } from './ReactCurrentFiber';
 import {resolveClassComponentProps} from './ReactFiberClassComponent';
@@ -2486,7 +2486,7 @@ export function commitMutationEffects(
 
   setCurrentDebugFiberInDEV(finishedWork);
   commitMutationEffectsOnFiber(finishedWork, root, committedLanes);
-  setCurrentDebugFiberInDEV(finishedWork);
+  resetCurrentDebugFiberInDEV();
 
   inProgressLanes = null;
   inProgressRoot = null;
@@ -3125,8 +3125,10 @@ export function commitLayoutEffects(
   inProgressLanes = committedLanes;
   inProgressRoot = root;
 
+  setCurrentDebugFiberInDEV(finishedWork);
   const current = finishedWork.alternate;
   commitLayoutEffectOnFiber(root, current, finishedWork, committedLanes);
+  resetCurrentDebugFiberInDEV();
 
   inProgressLanes = null;
   inProgressRoot = null;

packages/react-reconciler/src/ReactFiberCurrentOwner.js

@@ -1,16 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @flow
- */
-
-import type {Fiber} from './ReactInternalTypes';
-
-export let currentOwner: Fiber | null = null;
-
-export function setCurrentOwner(fiber: null | Fiber) {
-  currentOwner = fiber;
-}

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -78,8 +78,8 @@ import {
 import {
   isRendering as ReactCurrentFiberIsRendering,
   current as ReactCurrentFiberCurrent,
-  resetCurrentFiber as resetCurrentDebugFiberInDEV,
-  setCurrentFiber as setCurrentDebugFiberInDEV,
+  resetCurrentDebugFiberInDEV,
+  setCurrentDebugFiberInDEV,
 } from './ReactCurrentFiber';
 import {StrictLegacyMode} from './ReactTypeOfMode';
 import {

packages/react-reconciler/src/ReactFiberTreeReflection.js

@@ -24,7 +24,7 @@ import {
   SuspenseComponent,
 } from './ReactWorkTags';
 import {NoFlags, Placement, Hydrating} from './ReactFiberFlags';
-import {currentOwner} from './ReactFiberCurrentOwner';
+import {current as currentOwner, isRendering} from './ReactCurrentFiber';
 
 export function getNearestMountedFiber(fiber: Fiber): null | Fiber {
   let node = fiber;
@@ -90,7 +90,7 @@ export function isFiberMounted(fiber: Fiber): boolean {
 export function isMounted(component: React$Component<any, any>): boolean {
   if (__DEV__) {
     const owner = currentOwner;
-    if (owner !== null && owner.tag === ClassComponent) {
+    if (owner !== null && isRendering && owner.tag === ClassComponent) {
       const ownerFiber: Fiber = owner;
       const instance = ownerFiber.stateNode;
       if (!instance._warnedAboutRefsInRender) {

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -206,7 +206,6 @@ import {
   ContextOnlyDispatcher,
 } from './ReactFiberHooks';
 import {DefaultAsyncDispatcher} from './ReactFiberAsyncDispatcher';
-import {setCurrentOwner} from './ReactFiberCurrentOwner';
 import {
   createCapturedValueAtFiber,
   type CapturedValue,
@@ -232,8 +231,9 @@ import ReactStrictModeWarnings from './ReactStrictModeWarnings';
 import {
   isRendering as ReactCurrentDebugFiberIsRenderingInDEV,
   current as ReactCurrentFiberCurrent,
-  resetCurrentFiber as resetCurrentDebugFiberInDEV,
-  setCurrentFiber as setCurrentDebugFiberInDEV,
+  resetCurrentDebugFiberInDEV,
+  setCurrentDebugFiberInDEV,
+  resetCurrentFiber,
 } from './ReactCurrentFiber';
 import {
   isDevToolsPresent,
@@ -1686,9 +1686,8 @@ function handleThrow(root: FiberRoot, thrownValue: any): void {
   // These should be reset immediately because they're only supposed to be set
   // when React is executing user code.
   resetHooksAfterThrow();
-  resetCurrentDebugFiberInDEV();
   if (__DEV__ || !disableStringRefs) {
-    setCurrentOwner(null);
+    resetCurrentFiber();
   }
 
   if (thrownValue === SuspenseException) {
@@ -2386,7 +2385,9 @@ function performUnitOfWork(unitOfWork: Fiber): void {
     next = beginWork(current, unitOfWork, entangledRenderLanes);
   }
 
-  resetCurrentDebugFiberInDEV();
+  if (__DEV__ || !disableStringRefs) {
+    resetCurrentFiber();
+  }
   unitOfWork.memoizedProps = unitOfWork.pendingProps;
   if (next === null) {
     // If this doesn't spawn new work, complete the current work.
@@ -2394,10 +2395,6 @@ function performUnitOfWork(unitOfWork: Fiber): void {
   } else {
     workInProgress = next;
   }
-
-  if (__DEV__ || !disableStringRefs) {
-    setCurrentOwner(null);
-  }
 }
 
 function replaySuspendedUnitOfWork(unitOfWork: Fiber): void {
@@ -2408,7 +2405,6 @@ function replaySuspendedUnitOfWork(unitOfWork: Fiber): void {
   setCurrentDebugFiberInDEV(unitOfWork);
 
   let next;
-  setCurrentDebugFiberInDEV(unitOfWork);
   const isProfilingMode =
     enableProfilerTimer && (unitOfWork.mode & ProfileMode) !== NoMode;
   if (isProfilingMode) {
@@ -2501,7 +2497,9 @@ function replaySuspendedUnitOfWork(unitOfWork: Fiber): void {
   // The begin phase finished successfully without suspending. Return to the
   // normal work loop.
 
-  resetCurrentDebugFiberInDEV();
+  if (__DEV__ || !disableStringRefs) {
+    resetCurrentFiber();
+  }
   unitOfWork.memoizedProps = unitOfWork.pendingProps;
   if (next === null) {
     // If this doesn't spawn new work, complete the current work.
@@ -2509,10 +2507,6 @@ function replaySuspendedUnitOfWork(unitOfWork: Fiber): void {
   } else {
     workInProgress = next;
   }
-
-  if (__DEV__ || !disableStringRefs) {
-    setCurrentOwner(null);
-  }
 }
 
 function throwAndUnwindWorkLoop(
@@ -2902,11 +2896,6 @@ function commitRootImpl(
     const prevExecutionContext = executionContext;
     executionContext |= CommitContext;
 
-    // Reset this to null before calling lifecycles
-    if (__DEV__ || !disableStringRefs) {
-      setCurrentOwner(null);
-    }
-
     // The commit phase is broken into several sub-phases. We do a separate pass
     // of the effect list for each phase: all mutation effects come before all
     // layout effects, and so on.

packages/react-reconciler/src/ReactStrictModeWarnings.js

@@ -10,8 +10,8 @@
 import type {Fiber} from './ReactInternalTypes';
 
 import {
-  resetCurrentFiber as resetCurrentDebugFiberInDEV,
-  setCurrentFiber as setCurrentDebugFiberInDEV,
+  resetCurrentDebugFiberInDEV,
+  setCurrentDebugFiberInDEV,
 } from './ReactCurrentFiber';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import {StrictLegacyMode} from './ReactTypeOfMode';