fix: compatibility with react 19 in snapshots

[Filipoliko]

Summary

Remove react-is dependency in favor of custom implementation, which is compatible with both React 18 and React 19.

Resolves #15402

Test plan

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Filipoliko / name: Filipoliko (26a3968)

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commit: 26a3968

[Filipoliko]

I tried to create react-is fork inside pretty-print library to add compatibility layer between all react versions, but it is not possible due to Symbol.for('react.context') being treated as Context.Provider in React 19, but in React < 19 it is Context.Consumer. See this commit in react repository, which implements the change.

This change would make this PR breaking and it would also have incomplete support for older React versions.

I am leaving this PR open if somebody can give some hint about how to approach this problem, but right now, I am not sure how to accomplish full support for both React 18 and 19 at the same time.

Btw. Amazing testing coverage, the problem got discovered right away.

[cpojer]

I'd really prefer us not to take on the responsibility of maintaining this code. It will get out of sync more often than we think, and then we have to figure out the compatibility story each time.

Is there no way we can use react-is 19, and add a bunch of things around it so it correctly identifies pre react 19 elements?

[Filipoliko]

I don't really see a way to do this without having a custom implementation. Actually, I don't even see a way how to do this with a custom implementation, that will stay compatible with multiple major React versions.

In the beginning, I thought I can simply extend the test function (in ReactElement.ts) by adding some additional check next to ReactIs.isElement(val). But the problem turned out to be within the getType function, where we use for example ReactIs.isFragment (and other ReactIs.is<ReactComponentName> calls). Most of these ReactIs functions are using typeOf function under the hood, which we need to hijack in order to make react-is library return correct types. That is why I turned to copy-pasting the ReactIs implementation and customising it here and there. But that seems to be also a dead-end.

Right now, I would just wait for React v19 to be more widely used and then switch to it with next major release. If some people still use React v18, then they need to add the overrides configuration to their project -> #15402 (comment)

The only thing I am worried about is future React releases. If there is such a strong link between Jest and React versions, then this issue will keep reoccurring.

We could also make react-is library a peer dependency and make projects specify what version do they want (something like "react-is": "*"). But this is not very practical or user-friendly (but maybe better than overrides?).

We could also try to identify what react version is installed and select proper react-is implementation somehow, but I don't see an easy way how to do this.

I have no good solutions here.