react-hooks-js/set-state-in-effect

Validates against calling setState synchronously in an effect. This can indicate non-local derived data, a derived event pattern, or improper external data synchronization.

Validation prompt

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

Fires on a synchronous setState call inside useEffect's body: the textbook 'mirror prop into state on change' pattern that forces a wasted second render before paint.

Suppress when: useLayoutEffect that reads ref.getBoundingClientRect() (or another post-layout DOM measurement) and stores the result in state: the value cannot exist until after layout commits, and useLayoutEffect runs the extra render before paint.

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.

Derive the value during render and drop the state + effect entirely: const filtered = items.filter(...). For prop-driven full resets, pass key={prop} to the child to remount. For DOM-measured values, keep the setState but use useLayoutEffect so the extra render happens before the browser paints (avoiding a visible flash). See https://react.dev/reference/eslint-plugin-react-hooks/lints/set-state-in-effect

Repository-wide copy prompt

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