fix: projects should use collectCoverageFrom option

[jadutter]

TL;DR; running a single project defined in the projects config option fails to correctly use the collectCoverageFrom config option for that project.

Summary

I upgraded my nx repo to 19 and attempted to migrate from groups of tests defined as configurations in project.json, to using jest projects.
However, when I would run a single jest project, it would report the code coverage for the whole nx project instead of only the source code files being tested. This resulted in a non-zero exit code, causing nx to not cache the results (even when all the tests that ran passed).

I tried again with a non-mono repo and got the same result.
From what I can tell, a project config is meant to be nearly identical to the overall config, including using collectCoverageFrom.

I wrote up some tests to illustrate this behavior.

 FAIL  e2e/__tests__/multiProjectRunner.test.ts (9.321 s)
  correctly handle coverage reporting
    no projects option
      ✓ baseline (1044 ms)
      middleware with testNamePatterns
        ✓ without collectCoverageFrom within cli args (969 ms)
        ✓ with collectCoverageFrom within cli args (951 ms)
      controllers with testNamePatterns
        ✓ without collectCoverageFrom within cli args (942 ms)
        ✓ with collectCoverageFrom within cli args (727 ms)
    with projects option
      ✓ test all src code (998 ms)
      test middleware project
        ✕ without collectCoverageFrom within cli args (934 ms)
        ✓ with collectCoverageFrom within cli args (792 ms)
      test controllers project
        ✕ without collectCoverageFrom within cli args (907 ms)
        ✓ with collectCoverageFrom within cli args (670 ms)

I left comments in the test file PROJECT_COVERAGE_BUG_NOTE where the tests are failing, but ought to be passing.

While writing these tests, I came across some unexpected behavior. The stderr was missing some text I'd have expected, and when I ran it manually the text was present. I commented those out and left a POSSIBLE_BUG_NOTE comment.

Test plan

I wrote tests to check combinations of

• meets code coverage threshold vs not
• defines projects in the jest config vs not
• uses testPathPattern in the cli arguments vs not
• uses collectCoverageFrom in the cli arguments vs not (Contrasts how when the option is defined in a single project it is ignored)

Those tests can be run by

yarn jest e2e/__tests__/multiProjectRunner.test.ts

TODO

This is a draft, providing tests to check if all works as expected. What remains:

• write a fix
• update CHANGELOG.md
• clean up test file after fix is written
  • remove describe.only
  • change from using dir to DIR
• remove unused code
• lint

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