feat: Move @types/react-dom to optional peer dependencies

[eps1lon]

Closes https://github.com/testing-library/react-testing-library/issues/1184 Docs: https://github.com/testing-library/testing-library-docs/pull/1384

BREAKING CHANGE: @testing-library/dom was moved to a peer dependency and needs to be explicitly installed. This reduces the chance of having conflicting versions of @testing-library/dom installed that frequently caused bugs when used with @testing-library/user-event. @types/react-dom needs to be installed if you're typechecking files using @testing-library/react.

Type dependencies need to match their runtime counterpart. If foo is a dependency, @types/foo needs to be one as well. If foo is a peer dependency, @types/foo needs to be one as well. This is especially apparent if the constraint on foo spans multiple major versions. If we'd make @types/foo a direct dependency, users couldn't control which major version they get. Package managers would pick the highest. By moving @types/foo to peer dependencies, users can control which version of @types/foo they have.

In our case specifically, you'd get type mismatches of @types/react-dom if we just widen the peer dependency constraint from ^18 to ^18 | ^19. Currently, we're already compatible with the planned React 19 features so all we'd have to do is widen the constraint on release.

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[eps1lon]

do we maybe want to think about also move DTL to peerDeps?

I think so. Since DTL is stateful due to the config object, having multiple versions is problematic.

Ideally we wouldn't have the stateful config object to begin with but that requires a large refactor that needs coordination.

We don't need to rush this in this PR though. Could you help out and prepare docs and a commit making that change?

[MatanBobi]

We don't need to rush this in this PR though. Could you help out and prepare docs and a commit making that change?

Sure thing, I'll get to it later this week.

[MatanBobi]

@eps1lon Wdyt about making this change as part of a major too? https://github.com/testing-library/react-testing-library/issues/1277

Also, here's the PR to move DTL to peer: https://github.com/testing-library/react-testing-library/pull/1309

[eps1lon]

Also, here's the PR to move DTL to peer: https://github.com/testing-library/react-testing-library/pull/1309

Just push this commit to this branch. I don't want to go through the alpha branch shenanigans and just ship the major with one PR.

[MatanBobi]

Just push this commit to this branch. I don't want to go through the alpha branch shenanigans and just ship the major with one PR.

Done. I haven't fixed the conflicts though as we have more changes coming to that file.

[MatanBobi]

@eps1lon Do we want to push this one forwards after seeing that the latest major release looks ok?

[eps1lon]

We haven't got any reports recently so this seems safe now. I don't expect bugs that require big changes i.e. if something comes up it's likely small enough to warrant a backport.

Thank you for pushing this @MatanBobi

[MatanBobi]

Thanks @eps1lon. I've merged from main and fixed the conflicts we had so this is ready to be merged IMO.

[eps1lon]

Does feat! do anything for semantic-release?

[MatanBobi]

Does feat! do anything for semantic-release?

AFAIU no, it only uses the BREAKING CHANGE commit message, though I'm trying to follow conventional commit messages: https://www.conventionalcommits.org/en/v1.0.0/#commit-message-with--to-draw-attention-to-breaking-change

You can feel free to remove it if you want.

[eps1lon]

We're using semantic-release so we have to stick with what that tool understands.

[ph-fritsche]

Does feat! do anything for semantic-release?

If you like to switch to conventional commit, it's the default config here:

      - name: 🚀 Release
        uses: ph-fritsche/action-release@v2
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

[eps1lon]

Existing setup works for us so I'd rather not experiment.