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

Validation prompt

Confirm the detector match and collect the required evidence before deciding whether an edit is warranted.

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.

Suppress when: the function passed to the setter has hidden imperative side effects so it isn't really pure derivation.

Evidence boundary

The diagnostic proves only that the detector’s modeled source pattern matched. It does not prove runtime impact, product intent, rendered failure, or that one remediation is correct.

Establish the environment, repository policy, exceptions, and required rendered or runtime evidence before deciding the occurrence.

Record one outcome:

• Confirmed failure: The required evidence establishes the violation.
• Rejected: A documented exception or false-positive predicate applies.
• Needs evidence: Named evidence can still be collected.
• Unavailable: Required evidence cannot be collected in this run.
• Waived with evidence: An authorized, scoped exception applies to an established failure.
• Observation: The review records an optional tradeoff without claiming a defect.

A waiver records its scope, authority, evidence, and review condition. It is not a pass or false positive.

Default severity is registry metadata. Use the occurrence’s JSON severity after repository configuration when ordering real findings.

Fix prompt

Apply this candidate correction only after the required evidence confirms the risk.

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

Repository-wide copy prompt

Use this repository-wide prompt only after validating each occurrence. For one occurrence, use the guidance above.