`react-doctor/no-promise-then-side-effect-in-effect-without-catch`

Effect promise .then sets state with no catch

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

Validate the diagnostic

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

Confirm the reported code matches react-doctor/no-promise-then-side-effect-in-effect-without-catch. 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

const C = ({ urls }) => {
  const [, setValue] = useState();
  useEffect(() => {
    let request;
    for (const url of urls) {
      request = fetch(url).then((value) => setValue(value));
    }
    request.catch(() => setValue(null));
  }, [urls]);
};

Corrected pattern

const C = ({ urls }) => {
  const [, setValue] = useState();
  useEffect(() => {
    let isCurrent = true;
    for (const url of urls) {
      void fetch(url)
        .then((value) => {
          if (isCurrent) setValue(value);
        })
        .catch(() => {
          if (isCurrent) setValue(null);
        });
    }
    return () => {
      isCurrent = false;
    };
  }, [urls]);
};

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/no-promise-then-side-effect-in-effect-without-catch diagnostic in the current repository. Required change: - Handle rejections from effect promises. Clear loading state in finally, and ignore stale results after cleanup.

Reference transformation:Before:

const C = ({ urls }) => {
  const [, setValue] = useState();
  useEffect(() => {
    let request;
    for (const url of urls) {
      request = fetch(url).then((value) => setValue(value));
    }
    request.catch(() => setValue(null));
  }, [urls]);
};

After:

const C = ({ urls }) => {
  const [, setValue] = useState();
  useEffect(() => {
    let isCurrent = true;
    for (const url of urls) {
      void fetch(url)
        .then((value) => {
          if (isCurrent) setValue(value);
        })
        .catch(() => {
          if (isCurrent) setValue(null);
        });
    }
    return () => {
      isCurrent = false;
    };
  }, [urls]);
};

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/no-prop-callback-in-effect: Lift the shared state into a Provider so both sides read the same source — no useEffect-driven sync needed
react-doctor/no-prop-callback-in-render: Prop callback invoked during render
react-doctor/no-random-key: Replace the fresh-each-render key with a stable id from the item: key={item.id}
react-doctor/no-ref-callback-cleanup-before-react-19: Ref cleanup requires React 19
react-doctor/no-ref-current-in-render: Ref mutated during render

react-doctor/no-promise-then-side-effect-in-effect-without-catch