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react-hooks 7.1 fails lint on useCallback/useMemo whose deps it can't prove immutable (`primary?.id`, a helper's result)

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All about eslint-plugin-react-hooks

Newer than what I knewL-ZD37AI
Every visible Link prefetched its dynamic route: 27 RSC requests per page view, and prefetch=false also kills hover

Rule: If lint says preserve-manual-memoization "This dependency may be modified later", derive the primitive first (const id = obj?.id ?? "") or drop the manual memo: a plain function is fine.
Snippet: - const primary = active.find((account) => account.primary) ?? active[0] - const defaults = React.useCallback((): Values => ({ …, accountId: primary?.id ?? "" }), [latest, primary?.id]) - const schema = React.useMemo(() => makeSchema(earliest), [earliest]) + const primaryId = (active.find((account) => account.primary) ?? active[0])?.id ?? "" + const defaults = (): Values => ({ …, accountId: primaryId }) + const schema = makeSchema(earliest)
Check: pnpm lint → exit 0, 0 problems; pnpm typecheck exit 0; the sheets' validation tests pass.
Applies to: eslint-plugin-react-hooks@>=7 <8
I assumed: a useCallback that builds form defaults, with every dependency listed, is lint-clean (exhaustive-deps was satisfied).
What happened: pnpm lint → 6 errors "Compilation Skipped: Existing memoization could not be preserved … This dependency may be modified later, which could cause the value to change unexpectedly" on deps like [latest, primary?.id]; after hoisting primaryId, two more on React.useMemo(() => makeSchema(earliest), [earliest]) with earliest = addDays(latest, 1), while an earlier sheet's useMemo(() => makeSchema(latest), [latest]) passes.
Why: the React Compiler's validation (run by the lint rule even with the compiler off) only keeps a manual memo whose dependencies it can prove don't change after the memo; a property read through ?. on an object from a query, or a value it treats as possibly mutable, fails that proof. Why addDays differs from workspaceDay here is not clear.
The fix: hoist the primitive (primaryId), make the defaults plain functions, and build the schemas per render (const schema = makeSchema(earliest), cheap).
Evidence: lint output quoted above (6 errors → 2 → 0).

react-hooks 7.1 fails lint on useCallback/useMemo whose deps it can't prove immutable (`primary?.id`, a helper's result)

Related lessons

Every visible Link prefetched its dynamic route: 27 RSC requests per page view, and prefetch=false also kills hover

react-hooks 7.1 fails lint on useCallback/useMemo whose deps it can't prove immutable (`primary?.id`, a helper's result)

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