fix(jest-runtime): correctly report V8 coverage with resetModules: true

[mrazauskas]

Fixes #12904

Summary

Bumped into the same issue yesterday in one of my projects. Using resetModules: true option or calling jest.resetModules() breaks V8 coverage. Jest reports zero coverage for modules which were reset.

Problem

Seems like the root of the issue is this line: https://github.com/facebook/jest/blob/9806c906f32b91868b4a5712f962a96484bcdf8c/packages/jest-runtime/src/index.ts#L1158

Calling resetModules() clears off this._fileTransforms map which is needed later in V8 coverage logic (to detect if a file was executed and to map coverage to sources as well):

https://github.com/facebook/jest/blob/9806c906f32b91868b4a5712f962a96484bcdf8c/packages/jest-runtime/src/index.ts#L1206-L1217

Solution

Perhaps keeping a copy of sources for V8 in this._v8CoverageSources is the most optimal?

It is also possible to collect coverage results with each resetModule call. Not sure if that is good idea, because resetModule does not interrupt V8 anyhow.

Test plan

An e2e test, which is failing on main is added.

[SimenB]

great catch!

[mrazauskas]

Thanks! Just checked v28.1.1, now all works as expected.

[github-actions]

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