useMergedRef does not supports React 19's cleanup functions for refs

[elecdeer]

Dependencies check up

• I have verified that I use latest version of all @mantine/* packages

What version of @mantine/* packages do you have in package.json?

7.15.1

What package has an issue?

@mantine/hooks

What framework do you use?

Next.js

In which browsers you can reproduce the issue?

Not applicable – issue is not related to the browser

Describe the bug

React 19 supports cleanup functions for ref callbacks.
https://react.dev/blog/2024/12/05/react-19#cleanup-functions-for-refs

In React 18, ref functions were called with null when unmounting a component.
However, In React 19, a cleanup function is called at unmount time if ref returns a cleanup function, similar to how useEffect cleanup works.

The useMergedRef utility in Mantine currently does not handle these cleanup functions properly.

If possible, include a link to a codesandbox with a minimal reproduction

No response

Possible fix

No response

Self-service

• I would be willing to implement a fix for this issue

[rtivital]

You are welcome to submit a PR with a fix