[React 19] ForwardRef props are not referentially stable, breaking downstream memoizations #31613
Description
Summary
I don't know if this is a known behaviour or a bug, but something that's worth highlighting at least.
ForwardRef components are not deprecated, but they're not perfectly backwards compatible either.
The mere existance of ref prop on a ForwardRef component, even if undefined, makes the component props referentially unstable, breaking a whole host of downstream memoizations.
Reproduction:
https://codesandbox.io/p/sandbox/youthful-faraday-8m98cd?file=%2Fsrc%2FApp.tsx%3A34%2C23
If it's a known behaviour – please highlight this in the docs. Don't think we would have gone ahead with upgrading yet until some of our dependencies would be supporting React 19, because a whole host of packages (charting, datagrids, etc.) that are performance sensitive, suddenly had performance issues.
If not, it needs some attention, as it has pretty bad performance implications.
I believe a lot of maintainers are not dropping ForwardRef yet, because they think it's perfectly backwards compatible, and it's easier to maintain backwards compatibility for them.