feat(jest-runtime): share cacheFS between runtime and transformer

[ahnpnl]

Summary

Pass cacheFS from jest-runtime to ScriptTransformer. When getCacheKey or process is invoked, this cacheFS is passed in through transform options

If a transformer does module resolution and reads files, it should populate cacheFS so that Jest avoids reading the same files again, improving performance. cacheFS stores entries of <file path, file contents>

Close #10898

Test plan

Added unit test for jest-transform

[ahnpnl]

Node 14.x Windows, Node 12.x MacOS, Node LTS MacOS and facebook.jest failed but I have no idea what causes it.

[SimenB]

Node 14.x Windows, Node 12.x MacOS, Node LTS MacOS and facebook.jest failed but I have no idea what causes it.

macOS is flaky: #10828

[SimenB]

I wonder if we should pass it in the constructor rather than in the individual transform calls?

[ahnpnl]

Btw I could only modify test for jest-transform. For jest-runtime, I don't know which tests I can change to test the passing of cacheFS to ScriptTransformer.transform.

[ahnpnl]

I wonder if we should pass it in the constructor rather than in the individual transform calls?

I tried with constructor. However, when passing through constructor, cacheFS isn't updated for each test run.

[SimenB]

What do you mean "updated"?

[ahnpnl]

What do you mean "updated"?

For example, a simple project:

• When custom transformer is initialized, cacheFS has 100 elements

• Test file foo.spec.ts is processed. After processing, cacheFS in custom transformer shows 200 elements.

• A normal file foo.ts comes into custom trasnformer to be processed. However, cacheFS before processing this new file at this time shows 100 elements, which is the initial amount.

[ahnpnl]

hmm it seems like possible to pass through the constructor. I think I made mistakes somewhere previously

[SimenB]

this should update https://github.com/facebook/jest/blob/master/docs/CodeTransformation.md as well, other than that this LGTM 👍

[ahnpnl]

@SimenB please check :)

[SimenB]

thanks!

[thymikee]

Nice!

[SimenB]

Hmm, I wonder if it makes more sense to pass as part of TransformOptions rather than forcing people to implement createTransformer?

[ahnpnl]

Passing to getCacheKey transform options is also ok to me. Indeed if not implementing createTransformer, you won't get that cacheFS so it forces yes.

On the other hands, this cacheFS is partially related to transform options. It's related to transformer actually. Transform options to me is something directly related to how codes are transformed while this cacheFS is not directly related.

[SimenB]

Right, but createTransformer is also a "public" API (in that user can be expected to run it themselves) at which point that transformer won't get cacheFs passed. See e.g. https://jestjs.io/docs/en/tutorial-react#custom-transformers

[ahnpnl]

Hmm indeed, seem like we need to pass it as transform options then, unless others have other ideas

[ahnpnl]

Passing into getCacheKey as the last arg brings more benefits over extending TransformOption:

• Ensure that this arg is mandatory while passing via transform option requires cacheFS to be an optional property otherwise jest-repl will complain

• Since it’s not directly related to how codes are transformed, passing as independent arg ensures that.

• Users don’t have to be forced to implement create transformer function, as well as cover the case “public” API

[SimenB]

thanks!

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.