`react-doctor/class-component-missing-component-will-unmount-teardown`

Class component acquires a resource with no teardown

Category: Bugs
Severity: warn
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: react
Default: Enabled

Validate the diagnostic

Confirm the reported code matches this rule before you edit it.

Confirm the reported code matches react-doctor/class-component-missing-component-will-unmount-teardown. Compare it with the Before example and verify the same API, framework, and execution context. Treat it as a false positive only when one of those conditions differs.

Compare the code

The corrected pattern shows a focused way to address the diagnostic.

Reported pattern

class Listener extends React.Component {
  componentDidMount() {
    emitter.on("change", this.handleChange);
  }
  render() {
    return null;
  }
}

Corrected pattern

class Listener extends React.Component {
  componentDidMount() {
    emitter.on("change", this.handleChange);
  }
  componentWillUnmount() {
    emitter.off("change", this.handleChange);
  }
  render() {
    return null;
  }
}

How to fix

Use the corrected pattern as a reference. Preserve behavior that the rule does not require you to change.

Copyable fix prompt

Copy this self-contained prompt into your coding agent after you confirm the diagnostic.

Fix every confirmed react-doctor/class-component-missing-component-will-unmount-teardown diagnostic in the current repository. Required change: - Release listeners and timers acquired in componentDidMount/constructor by adding a componentWillUnmount that removes them (or use MobX disposeOnUnmount).

Reference transformation:Before:

class Listener extends React.Component {
  componentDidMount() {
    emitter.on("change", this.handleChange);
  }
  render() {
    return null;
  }
}

After:

class Listener extends React.Component {
  componentDidMount() {
    emitter.on("change", this.handleChange);
  }
  componentWillUnmount() {
    emitter.off("change", this.handleChange);
  }
  render() {
    return null;
  }
}

Constraints: - Confirm the reported code matches the Before pattern. - 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: react. Verification: - Run focused tests for the changed behavior. - Run React Doctor and confirm this diagnostic no longer appears. - Report the files changed and any checks you could not run.

More Bugs rules from the rules reference:

react-doctor/client-localstorage-no-version: Bake a version into the storage key (e.g. "myKey:v1"); a future schema change can ignore old data instead of crashing on it
react-doctor/debounce-no-cleanup: Memoized debounce never cancelled on unmount
react-doctor/effect-listener-cleanup-mismatch: Effect cleanup does not match its event listener
react-doctor/effect-listener-cleanup-reference-mismatch: Effect cleanup removes the wrong listener reference
react-doctor/effect-needs-cleanup: Return a cleanup function that releases the subscription / timer: `return () => target.removeEventListener(name, handler)` for listeners, `return () => clearInterval(id)` / `clearTimeout(id)` for timers, or `return unsubscribe` if the subscribe call already returned one

react-doctor/class-component-missing-component-will-unmount-teardown