useEffect Clean-Up Function Executes After Component is Removed

This behavior has changes in React version 17.0.x.

Clean-up function should execute when the component unmounts, and I've noticed in React v.17 by the time cleanup function executes, React referenced elements are no longer available.

Working example with React v.16
Example with React v.17

Notice unmountSuccessful logs before divRef in React v.17 example.

This is the only relevant change I noticed from the changelog.

If the behavior of useEffect clean-up has changed it should be reflected on the docs.

Code Snippet:

const App = () => {
  const divRef = React.useRef(null);
  
  React.useEffect(() => {
    console.log('divRef ::', divRef.current)
    return function cleanUp() {
      console.log('[cleanUp] divRef ::', divRef.current)
    }
  }, [])
  return (
    <div ref={divRef}>
      Open Browser's Console For Output
    </div>
  )
}

ReactDOM.render(
  <App />,
  document.getElementById('root')
);

const unmountApp = () => {
  console.log('unmounting root...')
  const node = document.getElementById('root');
  const unmountSuccessful = ReactDOM.unmountComponentAtNode(node);
  console.log('unmountSuccessful ::', unmountSuccessful)
};

window.setTimeout(unmountApp, 1500);

Start with the React useEffect documentation linked in the issue and compare its cleanup wording with the React 17 behavior shown in the two CodePen examples. Read the linked changelog pull request for the relevant change. Done means the documentation accurately explains when cleanup runs and whether referenced elements remain available.