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[Fiber] Ensure useEffectEvent reads latest values in forwardRef and memo() Components #34831

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Merged
merged 2 commits into from
Oct 13, 2025
+81 −5
Merged

[Fiber] Ensure useEffectEvent reads latest values in forwardRef and memo() Components #34831

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6d510c3
Current behavior for uEE in React.memo
eps1lon Oct 13, 2025
6bec011
[Fiber] Ensure Effect events read latest values in `forwardRef` and `…
eps1lon Oct 13, 2025
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8 changes: 3 additions & 5 deletions packages/react-reconciler/src/ReactFiberCommitWork.js
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Original file line number Diff line number Diff line change
Expand Up @@ -493,7 +493,9 @@ function commitBeforeMutationEffectsOnFiber(
}

switch (finishedWork.tag) {
case FunctionComponent: {
case FunctionComponent:
case ForwardRef:
case SimpleMemoComponent: {
if (enableUseEffectEventHook) {
if ((flags & Update) !== NoFlags) {
const updateQueue: FunctionComponentUpdateQueue | null =
Expand All @@ -510,10 +512,6 @@ function commitBeforeMutationEffectsOnFiber(
}
break;
}
case ForwardRef:
case SimpleMemoComponent: {
break;
}
case ClassComponent: {
if ((flags & Snapshot) !== NoFlags) {
if (current !== null) {
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78 changes: 78 additions & 0 deletions packages/react-reconciler/src/__tests__/useEffectEvent-test.js
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Expand Up @@ -850,4 +850,82 @@ describe('useEffectEvent', () => {
);
assertLog(['Add to cart', 'url: /shop/2, numberOfItems: 1']);
});

it('reads the latest context value in memo Components', async () => {
const MyContext = createContext('default');

let logContextValue;
const ContextReader = React.memo(function ContextReader() {
const value = useContext(MyContext);
Scheduler.log('ContextReader: ' + value);
const fireLogContextValue = useEffectEvent(() => {
Scheduler.log('ContextReader (Effect event): ' + value);
});
useEffect(() => {
logContextValue = fireLogContextValue;
}, []);
Comment on lines +865 to +866
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The original report registered an interval here. Even after rendering with a new context value, the interval continued to log the initial value.

return null;
});

function App({value}) {
return (
<MyContext.Provider value={value}>
<ContextReader />
</MyContext.Provider>
);
}

const root = ReactNoop.createRoot();
await act(() => root.render(<App value="first" />));
assertLog(['ContextReader: first']);

logContextValue();

assertLog(['ContextReader (Effect event): first']);

await act(() => root.render(<App value="second" />));
assertLog(['ContextReader: second']);

logContextValue();
assertLog(['ContextReader (Effect event): second']);
});

it('reads the latest context value in forwardRef Components', async () => {
const MyContext = createContext('default');

let logContextValue;
const ContextReader = React.forwardRef(function ContextReader(props, ref) {
const value = useContext(MyContext);
Scheduler.log('ContextReader: ' + value);
const fireLogContextValue = useEffectEvent(() => {
Scheduler.log('ContextReader (Effect event): ' + value);
});
useEffect(() => {
logContextValue = fireLogContextValue;
}, []);
return null;
});

function App({value}) {
return (
<MyContext.Provider value={value}>
<ContextReader />
</MyContext.Provider>
);
}

const root = ReactNoop.createRoot();
await act(() => root.render(<App value="first" />));
assertLog(['ContextReader: first']);

logContextValue();

assertLog(['ContextReader (Effect event): first']);

await act(() => root.render(<App value="second" />));
assertLog(['ContextReader: second']);

logContextValue();
assertLog(['ContextReader (Effect event): second']);
});
});
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