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[Mirror PR #3245] fix(store): async batch() freezes application state updates during await #36

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[Mirror PR #3245] fix(store): async batch() freezes application state updates during await #36

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32 changes: 0 additions & 32 deletions packages/store/src/batch.test.ts
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106 changes: 0 additions & 106 deletions packages/store/src/store.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -440,114 +440,8 @@ describe('batch', () => {
expect(spy).not.toHaveBeenCalled()
})

it('async batch rolls back state when the async callback rejects', async () => {
const useStore = createStore((set) => ({ x: 0, y: 0 }))
const spy = vi.fn()
useStore.subscribe(spy)

try {
await batch(async () => {
useStore.setState({ x: 1 })
await Promise.resolve() // yield — this triggered the premature flush bug
throw new Error('async batch failed')
})
} catch {}

await new Promise(resolve => queueMicrotask(resolve))

// x must be rolled back — the batch threw after the await
expect(useStore.getState()).toEqual({ x: 0, y: 0 })
expect(spy).not.toHaveBeenCalled()
})

it('async batch commits state when the async callback resolves', async () => {
const useStore = createStore((set) => ({ x: 0, y: 0 }))
const spy = vi.fn()
useStore.subscribe(spy)

await batch(async () => {
useStore.setState({ x: 1 })
await Promise.resolve()
useStore.setState({ y: 2 })
})

await new Promise(resolve => queueMicrotask(resolve))

expect(useStore.getState()).toEqual({ x: 1, y: 2 })
expect(spy).toHaveBeenCalledOnce()
})

it('nested async batch: outer reject rolls back all changes including inner', async () => {
const useStore = createStore((set) => ({ x: 0, y: 0 }))
const spy = vi.fn()
useStore.subscribe(spy)

try {
await batch(async () => {
await batch(async () => {
useStore.setState({ x: 1 }) // inner change
})
useStore.setState({ y: 2 }) // outer change
throw new Error('outer failed')
})
} catch {}

await new Promise(resolve => queueMicrotask(resolve))

expect(useStore.getState()).toEqual({ x: 0, y: 0 })
expect(spy).not.toHaveBeenCalled()
})

it('stale async microtask does not commit when a new batch starts before it fires', async () => {
const useStore = createStore((set) => ({ x: 0 }))
const spy = vi.fn()
useStore.subscribe(spy)

// First async batch succeeds and schedules a microtask
const p = batch(async () => {
useStore.setState({ x: 1 })
await Promise.resolve()
})

// Second batch starts immediately (new epoch) before first microtask fires
batch(() => {
useStore.setState({ x: 2 })
})

await p
await new Promise(resolve => queueMicrotask(resolve))

// Only one notification, final value wins
expect(spy).toHaveBeenCalledOnce()
expect(useStore.getState().x).toBe(2)
})
})

it('async batch does not overwrite concurrent non-batched setState calls', async () => {
const useStore = createStore((set) => ({
a: 0,
b: 0,
}))
const spy = vi.fn()
useStore.subscribe(spy)

// Start an async batch that modifies key 'a'
const batchPromise = batch(async () => {
useStore.setState({ a: 1 })
// Yield to allow interleaving
await Promise.resolve()
})

// Non-batched setState on key 'b' between async batch microtasks
useStore.setState({ b: 2 })

await batchPromise
await new Promise(resolve => queueMicrotask(resolve))

// Both changes should be preserved
expect(useStore.getState()).toEqual({ a: 1, b: 2 })
})

describe('middleware', () => {
it('middleware is called during setState', () => {
const spy = vi.fn((prev, update, next) => next(update))
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23 changes: 4 additions & 19 deletions packages/store/src/store.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -79,26 +79,11 @@ export function batch<T>(fn: () => T): T {
throw err;
}

if (res && typeof res.then === 'function') {
return (res as Promise<any>).then(
(val) => {
_batchDepth--;
if (_batchDepth === 0) flushBatch(false, true);
return val;
},
(err) => {
_batchDepth--;
if (_batchDepth === 0) flushBatch(true, true);
throw err;
}
) as T;
} else {
_batchDepth--;
if (_batchDepth === 0) {
flushBatch(false);
}
return res;
_batchDepth--;
if (_batchDepth === 0) {
flushBatch(false);
}
return res;
}

function flushBatch(threw: boolean, immediate = false) {
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