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);

Comienza con la documentación de React useEffect enlazada en la issue y compara su redacción sobre la limpieza con el comportamiento de React 17 mostrado en los dos ejemplos de CodePen. Lee el pull request del changelog enlazado correspondiente al cambio relevante. La tarea está terminada cuando la documentación explica con precisión cuándo se ejecuta la limpieza y si los elementos referenciados siguen estando disponibles.