`react-doctor/effect-observer-needs-disconnect`

Observer created in an effect never disconnected

Category: Bugs
Severity: error
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/effect-observer-needs-disconnect. 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

useEffect(() => {
  const observer = new ResizeObserver(onResize);
  observer.observe(node);
}, [node]);

Corrected pattern

useEffect(() => {
  const observer = new ResizeObserver(onResize);
  observer.observe(node);
  return () => observer.disconnect();
}, [node]);

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/effect-observer-needs-disconnect diagnostic in the current repository. Required change: - Return cleanup that calls disconnect() or unobserve(). This stops callbacks after unmount.

Reference transformation:Before:

useEffect(() => {
  const observer = new ResizeObserver(onResize);
  observer.observe(node);
}, [node]);

After:

useEffect(() => {
  const observer = new ResizeObserver(onResize);
  observer.observe(node);
  return () => observer.disconnect();
}, [node]);

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/effect-raf-loop-needs-cancel: requestAnimationFrame loop never cancelled
react-doctor/effect-remove-listener-inline-handler: removeEventListener called with a fresh inline handler
react-doctor/exhaustive-deps: Match the deps array to what the hook callback actually captures, or stabilize/move recreated values instead of blindly adding them.
react-doctor/expo-no-non-inlined-env: Use static dotted access: process.env.EXPO_PUBLIC_NAME (computed/destructured reads aren't inlined and are undefined at runtime)
react-doctor/form-control-requires-name: Form control is omitted from named submission data

react-doctor/effect-observer-needs-disconnect