ref(utils): Add functional updater support to useSessionStorage#111015
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ref(utils): Add functional updater support to useSessionStorage#111015
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Support SetStateAction<T> (function updater) in useSessionStorage's setter, matching React's useState API. This prevents stale-state bugs when multiple sequential calls spread the same snapshot, since each updater receives the latest prev value.
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Scope: Frontend
| setState(prev => { | ||
| const next = | ||
| typeof valueOrUpdater === 'function' | ||
| ? (valueOrUpdater as (prev: T) => T)(prev) |
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Why do we have to cast this?
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Cast is needed because TypeScript can't narrow SetStateAction<T> (T | ((prev: T) => T)) via typeof === 'function' when T could theoretically be a function type. Constraining T to exclude functions would fix the narrowing but results in a verbose generic signature for a general-purpose utility. Added a comment explaining the cast instead.
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evanpurkhiser
approved these changes
Mar 18, 2026
Ensures removeItem goes through React's setState queue, so it can't race with a pending wrappedSetState updater that would write the value back to storage after removal.
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Summary
SetStateAction<T>(function updater) inuseSessionStorage's setter, matching React'suseStateAPIprevvalueSplit out from #110883 per review feedback.
Test plan
CI=true pnpm test static/app/utils/useSessionStorage.spec.tsx-- 6 tests passing{a: 1}then{b: 2}results in{a: 1, b: 2})