feat: add support for snapshot matchers in concurrent tests

[dmitri-gb]

Summary

This implements support for snapshot matchers in concurrent tests. The long-standing issue with this has been rooted in the fact that because concurrent tests run in parallel there is no concept of a single currently running test and so jest-snapshot is not able to get this information from a global state object.

This problem can however be solved with AsyncLocalStorage, which is an object that can hold different values for different async contexts. Each concurrent test runs in its own async context and when asking for a value from the storage, gets a result that is unique to it.

Support is added only to jest-circus.

Test plan

There is a new integration test for this use-case.

Fixes #2180.
Fixes #5801.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dmitri-gb / name: Dmitri (564944c, 7cccbd5, fa25874, d53dfd8)

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[SimenB]

Hey! I landed #14045 which aims to solve the same issue, albeit with a new matcher. Do you think this PR adds additional value?

[mrazauskas]

To add my two cents: this PR looks like a better solution than new matcher.

1. The solution propose here makes the same matcher work in normal and constant modes. This means users can switch back and forth between the modes easily.
2. This solution does need any additional checks or lint rules. (See Add a rules to help with the .toMatchNamedSnapshot() matcher usage jest-community/eslint-plugin-jest#1367)
3. The toMatchSnapshot() and toMatchNamedSnapshot() are very similar. More API surface and not so clear when to use which.
4. toMatchNamedSnapshot() requires manually naming each snapshot. Hm.. That’s an extra step in contrary the solution proposed here simply works with toMatchSnapshot().

It is a pity that so much work went into toMatchNamedSnapshot() PR, but I would say it should be reverted. This PR should land instead to solve the issue.

[dmitri-gb]

I tend to agree with @mrazauskas. The fact that the same matcher can be used in concurrent and normal tests and that you don't need to give it an explicit name makes it more appealing to me.

[SimenB]

Yeah, I'm kinda convinced by that argument 😅

[SimenB]

https://github.com/jestjs/jest/releases/tag/v29.6.0

[nutchanon-c]

i bumped my jest to 29.6.0 and there are multiple concurrent tests in multiple describes in the same file, I think I'm still getting random snapshot names. Is this a known issue or an expected behaviour?

[SimenB]

#14335 is not released yet - might be it

[nutchanon-c]

Ohh I see. Thanks a lot. Can't wait for the release.

[SimenB]

@nutchanon-c new release is out - can you confirm it fixes your issue? If not, please open a new issue 🙂

[nutchanon-c]

It seems to fix the issue so far! If any new issues come up, I'll open a new issue later. Thank you very much!

[frenic]

Why is @types/node added in this PR?

"dependencies": {
    "@types/node": "*"
}

It just caused my non-node project to explode with type errors since Jest types are global and @types/jest depends on expect. I cannot see any obvious reason why this dependency needs to be added at all.

[dmitri-gb]

I added it because expect now imports a type from the Node.js module async_hooks. But you're right, this can probably be abstracted away such that this type import wouldn't be necessary. I'll try to fix this.

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