`react-doctor/no-derived-state-effect`

For derived state, compute inline: `const x = fn(dep)`. For state resets on prop change, use a key prop: `<Component key={prop} />`. See https://react.dev/learn/you-might-not-need-an-effect

Category: State & Effects
Severity: warn
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: always

Validation prompt

Use this to decide whether a fired diagnostic is real or a false positive.

Fires when a useEffect (non-empty deps) contains ONLY setter calls whose arguments derive entirely from identifiers in the deps. Three message variants branch on the setter argument shape: state reset (no dep referenced — suggests a key prop), wrap in useMemo (a user-defined function call appears), or compute during render. Math/Date/JSON-rooted calls and TRIVIAL_DERIVATION_CALLEE_NAMES are exempted. False positive: the function passed to the setter has hidden imperative side effects so it isn't really pure derivation.

Fix prompt

Use this once validation confirms the diagnostic is real.

For cheap derivation, drop the effect and compute inline: const value = transform(dep). For expensive computation, wrap in useMemo: const value = useMemo(() => transform(dep), [dep]). For resetting all child state on a prop change, pass the prop as a key — <Component key={prop} /> — rather than syncing via an effect. See https://react.dev/learn/you-might-not-need-an-effect