diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js index 1c1f2e6099373..7538bb9b3c217 100644 --- a/packages/react-reconciler/src/ReactFiberHooks.new.js +++ b/packages/react-reconciler/src/ReactFiberHooks.new.js @@ -1615,7 +1615,7 @@ function updateSyncExternalStore( } } } - const prevSnapshot = hook.memoizedState; + const prevSnapshot = (currentHook || hook).memoizedState; const snapshotChanged = !is(prevSnapshot, nextSnapshot); if (snapshotChanged) { hook.memoizedState = nextSnapshot; diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js index f9fac9358ad7b..e98d684a78e6f 100644 --- a/packages/react-reconciler/src/ReactFiberHooks.old.js +++ b/packages/react-reconciler/src/ReactFiberHooks.old.js @@ -1615,7 +1615,7 @@ function updateSyncExternalStore( } } } - const prevSnapshot = hook.memoizedState; + const prevSnapshot = (currentHook || hook).memoizedState; const snapshotChanged = !is(prevSnapshot, nextSnapshot); if (snapshotChanged) { hook.memoizedState = nextSnapshot; diff --git a/packages/react-reconciler/src/__tests__/useSyncExternalStore-test.js b/packages/react-reconciler/src/__tests__/useSyncExternalStore-test.js index d2b838aebe0c0..804e40ca21afc 100644 --- a/packages/react-reconciler/src/__tests__/useSyncExternalStore-test.js +++ b/packages/react-reconciler/src/__tests__/useSyncExternalStore-test.js @@ -18,6 +18,7 @@ let useLayoutEffect; let forwardRef; let useImperativeHandle; let useRef; +let useState; let startTransition; // This tests the native useSyncExternalStore implementation, not the shim. @@ -36,6 +37,7 @@ describe('useSyncExternalStore', () => { useImperativeHandle = React.useImperativeHandle; forwardRef = React.forwardRef; useRef = React.useRef; + useState = React.useState; useSyncExternalStore = React.useSyncExternalStore; startTransition = React.startTransition; @@ -173,4 +175,33 @@ describe('useSyncExternalStore', () => { }); }, ); + + test('next value is correctly cached when state is dispatched in render phase', async () => { + const store = createExternalStore('value:initial'); + + function App() { + const value = useSyncExternalStore(store.subscribe, store.getState); + const [sameValue, setSameValue] = useState(value); + if (value !== sameValue) setSameValue(value); + return ; + } + + const root = ReactNoop.createRoot(); + act(() => { + // Start a render that reads from the store and yields value + root.render(); + }); + expect(Scheduler).toHaveYielded(['value:initial']); + + await act(() => { + store.set('value:changed'); + }); + expect(Scheduler).toHaveYielded(['value:changed']); + + // If cached value was updated, we expect a re-render + await act(() => { + store.set('value:initial'); + }); + expect(Scheduler).toHaveYielded(['value:initial']); + }); });