docs: remove github-actions-cpu-cores recommendation

[blimmer]

Summary

As of Jest 29.4.0, you no longer need to use the github-actions-cpu-cores action to properly set --max-workers. All that action does is use os.availableParallelism(), which jest now does natively after #13738.

Test plan

Docs only

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• ✅ login: blimmer / name: Ben Limmer (92551e8)

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[blimmer]

Alternatively, we could leave this and add an info section that it's necessary beyond 29.4.0

[SimenB]

While that API has been backported to node 18, it has not been backported to v14 or v16, both of which Jest still supports.

I'm happy to tweak the docs to point that out, but I don't think we should remove it yet.

[blimmer]

Ah, good to know. I've updated this PR - feedback on phrasing is welcome.

[blimmer]

@SimenB , given what you said, is the action inaccurately configured? https://github.com/SimenB/github-actions-cpu-cores/blob/a0a2b80333e58828f914f98cfffe6d91350afa9d/action.yml#L6-L8

It appears to be running on Node 16, which doesn't have the availableParallelism method.

[SimenB]

It's forward compatible 😀

Runners are only available using Node 12 (deprecated) and 16: https://github.blog/changelog/2022-05-20-actions-can-now-run-in-a-node-js-16-runtime/

[blimmer]

Gotcha. I guess I'm a little bit confused when this action would be useful, then. From what I can gather, as configured, it's using os.cpus().length, which is built into Jest and has been available since Node 14.

Testing this on a sample GitHub action, it looks like os.cpus().length is properly returning 2 CPUs on the default runner.

If os.cpus.length() was returning an invalid response and the github-actions-cpu-cores could opt into Node 18+ (for os.availableParallelism()), I could see why you'd want to use it.

Could you help me understand a concrete scenario where this action would be better than the default Jest behavior?

[SimenB]

#10653 (comment)

Jest's default implementation is to leave one core alone, though, which is why I specify it

As mentioned there though, we can probably stop doing - 1 on CI. I'd consider that a breaking change tho (if people do CI=1 npx jest locally, we'd swamp their resources)

[blimmer]

Ah, OK, thanks for the explanation. I understand now why the action is helpful. I agree that using all cores on CI by default (with a major version bump) would be a nice improvement. I'll just close this for now. Thanks!

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