[core] Enable innerRef on Backdrop, List, MenuList and Paper

[eps1lon]

Enables innerRef on Backdrop, List, MenuList and Paper. These are the components where we currently are attaching refs for findDOMNode.

This is step 1 in #13676 (comment) and a prerequisite for #13676.

patch-package is only a temporary workaround until reactjs/react-docgen#311 gets merged. If it doesn't get merged before v4 I would suggest we use a fork instead of patching transpiled files.

PS: I would hold off for now on forwarding refs for all components. I generally follow the argument that it's breaking component abstraction and we can always add forwarding refs later on if the use case makes sense. I would however also argue that forwarding refs on components that are clearly meant to render a DOM node (e.g. a Button or List component) is not an issue as long we are defining the interface as basic as possible. For example defining that the ref on Button returns a button HTML element will likely block us if we decide to use a div in the future. However saying that the ref is a generic HTML element is not bad at all in my opinion. Since react-dom does not support all use cases yet (e.g. focus or passive event listeners) we still need access to the actual DOM.

[eps1lon]

See facebook/react#14319 for full explanation.

[oliviertassinari]

It's a naive question. Do we need the forwardRef complexity if React ships reactjs/rfcs#97?

[eps1lon]

It's an incomplete and open RFC. I don't know what your timeline is but if we want to be strict mode compatible in v4 then we not only have to delay indeterminately until the RFC is settled. We also have to wait for it to be implemented, released and use that version as a peer dependency. Those are quite a bit of unknowns.

I'm not sure what you mean by complexity. The only complexity I can see right now is waiting for reactjs/react-docgen#311 to be released.

I don't want to merge this right now. I'd rather wait for the docgen feature to be released than introduce patch-package.

[eps1lon]

With the release of react-docgen@3 patch-package is no longer required. This PR is green from my point.

@oliviertassinari Are you ok with merging this PR or do you want to wait for the fragment ref implementation?

[oliviertassinari]

@eps1lon I don't have a strong feeling about each outcome.

1. I doubt a lot of people use the strict mode. I wish we had the Fragment ref.
2. I guess we can revert once we have the Fragment ref.

[eps1lon]

1. I doubt a lot of people use the strict mode. I wish we had the Fragment ref.

Don't forget ConcurrentMode or createRoot which enfore strict mode.