react-hooks-js/use-memo

Validates usage of the useMemo() hook against common mistakes. See [`useMemo()` docs](https://react.dev/reference/react/useMemo) for more information.

Validation prompt

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

Fires on a useMemo whose callback has no return statement (it falls through and the memo's value is undefined). The cached value is therefore always undefined, making the hook useless and almost certainly indicating the wrong hook was chosen.

Suppress when: a deliberately-empty stub left during refactoring: but the right fix is still to remove or repurpose it.

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.

Add an explicit return for the computed value: useMemo(() => data.map(transform), [data]). If the body is purely side effects (analytics, logging, DOM writes), switch to useEffect for synchronization-style work or move the call into the event handler that triggers it. useMemo is for caching expensive computations, not for running code on dep change. See https://react.dev/reference/eslint-plugin-react-hooks/lints/use-memo

Repository-wide copy prompt

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