react-doctor/prefer-use-sync-external-store

Replace a manual external-store subscription with useSyncExternalStore while preserving subscribe receiver semantics and stable snapshots

Validation prompt

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

Requires a 4-vertex match: useState(getSnapshot()) paired with useEffect(() => { const u = store.subscribe(() => setX(getSnapshot())); return u; }, []) where the setter's argument is structurally identical to the initializer and cleanup releases the subscription. Confirm getSnapshot returns a cached/stable value when the store is unchanged, whether subscribe depends on its receiver, and what initial server snapshot hydration requires.

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.

Replace the state/effect pair with useSyncExternalStore. If subscribe is a receiver-sensitive method, preserve it with listener => store.subscribe(listener) instead of passing an unbound method. Ensure getSnapshot returns the same cached value while the store is unchanged. During SSR, pass getServerSnapshot and make its value match the first client snapshot, usually by serializing the initial store data. See https://react.dev/reference/react/useSyncExternalStore

Repository-wide copy prompt

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