[Suggestion]: clarify behaviour of ref callbacks

[OliverJAsh]

Summary

The described behaviour for ref callbacks with null as an argument is ambiguous.

Page

https://react.dev/reference/react-dom/components/common#ref-callback

Details

From https://react.dev/reference/react-dom/components/common#ref-callback:

React will also call your ref callback whenever you pass a different ref callback. In the above example, (node) => { ... } is a different function on every render. When your component re-renders, the previous function will be called with null as the argument, and the next function will be called with the DOM node.

If I understand correctly, the emphasised sentenced is not correct when the ref callback returns a clean up function, as is the case in the referenced example. This needs to be clarified.

There is a note later on which helps a bit, but I still think this sentence could be made clearer so it makes sense in isolation.

Reduced test case to confirm this behaviour: https://stackblitz.com/edit/vitejs-vite-2r9rn6m2?file=src%2FApp.tsx&terminal=dev

[rickhanlonii]

Yeah this could be cleaned up, want to submit a PR to improve it? It should probably flip so it emphasizes the ref callback pattern and has a note about legacy support with passing null when there's no cleanup.