react-doctor/no-is-mounted
Disallow the removed legacy isMounted() API: cancel async work instead of guarding setState.
- Status
- Active
- Category
- Correctness
- Assessment
- Evidence-required risk
- Required evidence
- source code
- Default configuration
- Enabled
- Default severity
- warn
Show technical metadata
- Scope
- All supported frameworks
- Active when
- always (unless customRulesOnly=true)
- Requirements
- react
- Priority
- 30 (P3)
- Source
- oxlint-plugin-react-doctor
- Rule set
- oxlint-plugin-react-doctor 0.9.3 (prompt schema 2)
- Documentation
- Official documentation
Validation prompt
Confirm the detector match and collect the required evidence before deciding whether an edit is warranted.
Fires on this.isMounted() calls inside React class components (React.Component subclasses and createReactClass factories). The legacy isMounted() API was removed and is universally treated as an anti-pattern: it was used to silence "Can't call setState on an unmounted component" warnings while masking real subscription/listener leaks. The rule is scoped to React class bodies, so an unrelated class with its own isMounted method is not a false positive.
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.
Cancel the async work instead of guarding setState: use an AbortController for fetch, unsubscribe in componentWillUnmount, or return a cleanup function from useEffect. If you must track mount state, set this._isMounted in componentDidMount and clear it in componentWillUnmount as a temporary shim until you migrate the class to a function component with hooks. See https://oxc.rs/docs/guide/usage/linter/rules/react/no-is-mounted.html
Repository-wide copy prompt
Use this repository-wide prompt only after validating each occurrence. For one occurrence, use the guidance above.
Show repository-wide prompt
Fix every confirmed react-doctor/no-is-mounted diagnostic in the current repository.
Required change:
- Cancel the async work instead of guarding setState: use an AbortController for fetch, unsubscribe in componentWillUnmount, or return a cleanup function from useEffect. If you must track mount state, set this._isMounted in componentDidMount and clear it in componentWillUnmount as a temporary shim until you migrate the class to a function component with hooks. See https://oxc.rs/docs/guide/usage/linter/rules/react/no-is-mounted.html.
Validation before editing:
Fires on this.isMounted() calls inside React class components (React.Component subclasses and createReactClass factories). The legacy isMounted() API was removed and is universally treated as an anti-pattern: it was used to silence "Can't call setState on an unmounted component" warnings while masking real subscription/listener leaks. The rule is scoped to React class bodies, so an unrelated class with its own isMounted method is not a false positive.
Constraints:
- Make the smallest change that fixes the root cause.
- Preserve behavior and interfaces unrelated to this diagnostic.
- Reuse existing project components, utilities, and conventions.
- Do not introduce render-phase side effects, render-phase state updates, or Hooks rule violations.
- Adapt identifiers and framework details instead of copying blindly.
- Do not disable the rule or suppress matching code.
- Confirm this rule is enabled for the project:
always (unless customRulesOnly=true).
Assessment:
- Record detector evidence, applicability facts, assumptions, missing evidence, and the rule class for this occurrence.
- Return one outcome: Confirmed failure, Rejected, Needs evidence, Unavailable, Waived with evidence, or Observation.
- A waiver records the established failure, scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.
Verification:
- Run focused tests for the changed behavior.
- Run React Doctor and confirm this diagnostic no longer appears from changed code.
- Run an unfiltered scan of the affected scope before claiming no cross-category regression.
- Report the files changed and any checks you could not run.