react-doctor/no-legacy-class-lifecycles

Migrate legacy pre-commit class lifecycles to concurrent-safe patterns; their UNSAFE_ aliases remain available but deprecated in React 19

Validation prompt

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

Fires when a class body (ClassBody) contains a MethodDefinition or PropertyDefinition whose key Identifier is exactly componentWillMount, componentWillReceiveProps, or componentWillUpdate, OR their UNSAFE_-prefixed aliases: a pure name match, class-body-scoped (object-literal methods, standalone functions, or these names used as variables never fire). Confirm the enclosing class is a mounted React component and review the lifecycle's intent. Both the legacy names and their UNSAFE_ aliases are deprecated because they are unsafe with concurrent rendering; the UNSAFE_ forms remain documented and executable in React 19. Suppress a class that is not a React component but coincidentally defines the same method name.

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.

Map each legacy hook to the replacement that matches its intent rather than merely renaming it. Move componentWillMount side effects and subscriptions to componentDidMount, and put pure initial field or state setup in the constructor. Prefer deriving values during render; when state truly must adjust to prop changes, use the narrowest documented pattern, and move prop-driven side effects to a guarded componentDidUpdate. Move pre-update DOM reads to getSnapshotBeforeUpdate and consume the snapshot in componentDidUpdate. Keeping an UNSAFE_ alias can be a temporary compatibility step, but it does not make the lifecycle concurrent-safe. See https://react.dev/reference/react/Component#unsafe_componentwillreceiveprops

Repository-wide copy prompt

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