Allow jest.config.cts

[DerTimonius]

Summary

This PR will allow loading jest.config.cts files for ESM projects like proposed in PR #14064 and issue #13118
Additionally, this PR will add fixtures and snapshots that should fix the tests.

Closes #14064

Test plan

[mrazauskas]

Good idea. These are the missing parts:

• change log entry
• some integration tests here (perhaps: to check that it works, and that type errors are reported as expected): https://github.com/facebook/jest/blob/main/e2e/__tests__/tsIntegration.test.ts
• documentation should be altered here: https://github.com/facebook/jest/blob/15af9b3b6f53a4f2f2e39d328eb6ef9f46ba91c4/docs/Configuration.md?plain=1#L8

[DerTimonius]

@mrazauskas Thanks for the hints, I added some things now, please tell me if something is missing 🙂

[mrazauskas]

Thanks!

Did you try running these new e2e tests? To do so, you build the repo and run yarn test-ts --selectProjects ts-integration. It is passing on main, but if I checkout your branch few tests fail. They all have "CTS config" in their names.

[DerTimonius]

Interesting, I ran yarn test after writing the tests and did not get any errors. Will get into this later today!

[DerTimonius]

I investigated the failing tests and was able to recognize two separate issues:

1. I can't use imports
2. TS is not really working in those files. I tried a different strategy to import the Config type and got the following error:

"const config: Config.InitialOptions = {displayName: 'ts-object-config', verbose: true};\n" +
        '      ^^^^^^\n' +
        '\n' +
        'SyntaxError: Missing initializer in const declaration\n' +

I then tried to move it to the back using as Config.InitialOptions but this also did not work.

I don't have any idea how to solve this...

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The committers listed above are authorized under a signed CLA.

• ✅ login: DerTimonius / name: Timon Jurschitsch (faa4fff, 2e0088b, 19ade29, a5690d3, 80bbbf6, bf0e377, f528d35, a8cdf6d)
• ✅ login: SimenB / name: Simen Bekkhus (cddd949, b57de1f, 28e1b1e, a71fab1)

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[DerTimonius]

Still trying, but still really have no idea how to fix the issue that the .cts files appear not to be recognized as valid TypeScript...
Maybe some hints?

[karlhorky]

@DerTimonius can you post a new short summary about what the problem is?

From the error message and your conclusions above, it seems like the tests are not running .cts files as TypeScript - maybe as part of your summary, check into how the tests are running Jest? Maybe also useful would be to check if Jest works with .cts files outside of the testing environment.

Maybe @mrazauskas can assist...?

[karlhorky]

One thing that I can see without looking too deeply into it is that you have an export in your .cts file:

Since .cts is compiled to CommonJS, maybe you need to use the module.exports = {} format as you see in the other jest.config.cjs fixture:

jest/packages/jest-cli/src/init/__tests__/__fixtures__/has-jest-config-file-cjs/jest.config.cjs

Lines 1 to 8 in cddd949

	/**
	* Copyright (c) Meta Platforms, Inc. and affiliates.
	*
	* This source code is licensed under the MIT license found in the
	* LICENSE file in the root directory of this source tree.
	*/
	module.exports = {};

[karlhorky]

Ah no, I'm wrong about that, export keyword is just fine:

https://github.com/withastro/astro/blob/d2020c29cf285e699f92143a70ffa30a85122bb4/packages/integrations/svelte/src/editor.cts

[DerTimonius]

@karlhorky Sure. The issues I'm currently facing are solely in the new integration tests that were necessary to write.

Initially I got an error, telling me that I can't use import in the .cts files. I changed the type import, but I'm pretty sure that this is the first issue.
If I'm running the tests now I get the following error

"const config: Config.InitialOptions = {displayName: 'ts-object-config', verbose: true};\n" +
        '      ^^^^^^\n' +
        '\n' +
        'SyntaxError: Missing initializer in const declaration\n' +

It appears to me that the normal TypeScript code is not recognized as such - if I change the code to this:

const config = {displayName: 'ts-object-config', verbose: true} as Config.InitialOptions

I get almost a different error, telling me that as is an unknown token.

What I tried so far

• I looked a bit in the TS docs regarding .cts files and found that maybe it is necessary to add "module": "NodeNext" to the tsconfig.json file. I then put it in the tsconfig of the e2e directory, but still got the same errors.
• I then tried to adapt the tsconfig.json file in the root dir by adding "module": "NodeNext". The errors remained the same.
• I then looked if maybe somewhere in the code the possibility for .cts files is missing and need to be added, but I'm not sure where this should be the case.

[github-actions]

This PR is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[SimenB]

Hiya, sorry about the radio silence. Let's get this in 🙂

I tried to merge in main - the only conflict was in the changelog, but it seems like there might have been other changes causing test failures?

[DerTimonius]

Hi @SimenB
thanks for your response!
I had issues with the tests before, because the .cts files were not recognized as TS files - so typical TS syntax did throw errors. I will take a look into this later today, maybe there has been an update somewhere that solved this in some way?

[DerTimonius]

Still getting the same errors that I mentioned above (#14070 (comment))

I really don't get this error: writing TS code in a .cts file and it's not recognized...

[github-actions]

This PR is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[SimenB]

Suggested change

	const isTS = configPath.endsWith(JEST_CONFIG_EXT_TS || JEST_CONFIG_EXT_CTS);
	const isTS =
	configPath.endsWith(JEST_CONFIG_EXT_TS) ||
	configPath.endsWith(JEST_CONFIG_EXT_CTS);

@DerTimonius I think this is your issue - cts was never considered

[DerTimonius]

oh man. you're right 🙈
implemented this change with the last commit and fixed the tests (all running locally! they did not before, so this is a huge improvement)

[SimenB]

nice! seems like we just need to fix packages/create-jest/src/__tests__/init.test.ts and it's good to go

[DerTimonius]

Hm, I don't know why the last check is failing. I did not remove the file in question: /home/runner/work/jest/jest/packages/jest-cli/src/init/__tests__/tsconfig.json

[SimenB]

packages/jest-cli/src/init/ have been moved to packages/create-jest - this is probably some remnant of that?

#14490

[SimenB]

thanks!

[karlhorky]

@SimenB @DerTimonius thanks for the PR, review and merge!

Look forward to trying this out in a release! Will this be a part of jest@29.8.0 or jest@30.0.0?

[karlhorky]

@SimenB if the next minor or major releases are still going to be pending for a while, what do you think of creating and publishing a new alpha release eg. jest@30.0.0-alpha.3?

[karlhorky]

Nice, this has been released in jest@30.0.0-alpha.3 🎉

• https://github.com/jestjs/jest/releases/tag/v30.0.0-alpha.3

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