When setting state after a component was unmounted, React should log the following error:

Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.

However, If I'm returning an empty function as the cleanup function it would not log the error.

the code:

const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

function Comp() {
  const [state, setState] = useState("nothing");

  useEffect(() => {
    setState("loading");

    sleep(1000).then(() => {
      console.log("setting state");
      setState("finished");
    });

    // When the below return exists it does not log the error
    return () => {};
  }, []);

  return <span>{state}</span>;
}

export default function App() {
  const [show, setShow] = useState(true);

  useEffect(() => {
    sleep(500).then(() => setShow(false));
  }, []);

  return (
    <div className="App">
      <h1>
        <button onClick={() => setShow((v) => !v)}>Show</button>
        {show && <Comp />}
      </h1>
    </div>
  );
}

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