fix: export new act when available

[MatanBobi]

Resolves https://github.com/testing-library/react-testing-library/issues/1316

What: This PR exports the correct act if available to avoid deprecation warnings.

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[MatanBobi]

How did you test this?

I've used npm link locally to see that the error is there before I link and removed after I link. Having said that, I wasn't able to install an older type of react and react-dom (to see that the type is exported properly when act isn't exported from react), for some reason I always get the same d.ts files which show act from test-utils as deprecated and act from react exported so that's odd.

From your comment, I realized that we probably also need to define @types/react as a peer dependency now? I saw that it's a dependency for @types/react-dom so I'm not sure if we want to rely on that or not.

Edit: I think I understand what happened, since @types/react-dom is our dependency and not a peer yet, this scenario is impossible because the types are bundled in our code. I'm always getting the types we install as part of RTL (as long as it's not a peer).

[eps1lon]

Yeah I don't think this ever worked for versions where react-dom/test-utils didn't have act.

TypeScript should error if you try to import something that doesn't exist.

We probably need to @ts-ignore the React.act import and then check if it's any (typeof act extends never ? true : false) instead of undefined.

Let's double check this works in versions without React.act by forcing an older version of @types/react via overrides (npm) or resolutions (yarn, pnpm). Make sure to clear lockfile and node_modules if you use npm.

[eps1lon]

And we also need @types/react as an optional peer dependency. We always needed that though since we already use React.ReactNode. It just happened to work because TypeScript always makes namespaces available globally.

[MatanBobi]

Using overrides didn't help as I'm using link so the dependency is still taken locally. I've tried installing an older version of @types/react and @types/react-dom and link. Things seem to work. I've pushed the fixes. I'll also create a PR to the docs site to state that users will probably want to install @types/react as it's a peer dependency now.

[MatanBobi]

Following your idea @eps1lon, I've created this repo for repro: https://github.com/MatanBobi/rtl-deprecated-act-repro Main branch is old React (18.2.0) that shows no regression with type change, other two branches are:

1. New React (18.3.1) without type change - shows deprecation message.
2. New React (18.3.1) with type change - no deprecation message.

[MatanBobi]

@eps1lon Related docs PR: https://github.com/testing-library/testing-library-docs/pull/1390

[mwegter95]

Yesss thank you. This helped me. When I saw your post, I downloaded the latest version and my program started running, no warning after that. Tyty

npm install @testing-library/react@latest @testing-library/jest-dom@latest