jest --only-changed ignores changes to module mocks

[tomasz-sodzawiczny]

🐛 Bug Report

jest --only-changed does not take mocks into consideration when choosing the tests to run.

To Reproduce

Steps to reproduce the behavior (see example repo):

• module ./a depends on module ./b
• module ./b is mocked in the test of './a`
• you change the mock of module ./b

Expected behavior

Test of module ./a is run when running jest --only-changed.

The success of the test depends on changes of the mock file - so changing the mock should trigger the test - the same way as changing ./b directly does.

The scenario is not uncommon - could happen when someone is extending the functionality of ./b, or works on another module that depends on it.

Link to repl or repo

https://github.com/tomasz-sodzawiczny/jest-only-changed-vs-mocks

envinfo

Probably not important, but:

System:
    OS: macOS 10.14.5
    CPU: x64 Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
  Binaries:
    Node: 12.4.0 - ~/.nvs/node/12.4.0/x64/bin/node
    Yarn: 1.17.3 - /usr/local/bin/yarn
    npm: 6.9.0 - ~/.nvs/node/12.4.0/x64/bin/npm
  npmPackages:
    jest: ^24.9.0 => 24.9.0

[SimenB]

The code for this lives in https://github.com/facebook/jest/blob/c588c18595000d68c98bf8c72d003ff8b3674124/packages/jest-resolve-dependencies/src/index.ts

A PR fixing this is very much welcome! 🙂

[petevdp]

I'm a first time contributer and I'd like to tackle this, but if anyone has the time I'd like some initial feedback on how I should tackle this problem.

I've done some digging and I've found this file dependencyExtractor, which has some regex patterns it uses to find dependency declarations, indirectly supplying the resolver in the file linked by @SimenB with dependencies for files.

Other patterns matching jest.requireMock are present, but not jest.mock.

dependencyExtractor also doesn't include the mocks themselves as dependencies, only the files that are being mocked. I'm guessing that there's a reason it's like this but maybe not.

So with all that in mind, would a viable solution be to expand the regexes and add the mock files as dependencies where applicable?

If not, some alternatives would be to:

• Alter the output signature of the extractor to seperate mock dependencies, and the fileMetaData type and any associated types/
• Change DependencyResolver.resolve to cross reference any mocks known to the resolver against dependencies being checked, and including matching mocks without using any additional file metadata. This would have the drawback of including mocks as dependencies which aren't actually utilized, but is probably the solution with the fewest side effects.

Any feedback is welcome!

[jeysal]

It's hard to tell without trying it out and seeing what else might break, but I believe changing jest-resolve-dependencies is the cleanest way.

including mocks as dependencies which aren't actually utilized

I think this is tolerable, and will only rarely cause tests being run unnecessarily in practice. I also believe that it's very hard to avoid, because finding out if a mock is used is not easy (it could be declared to be used in lots of places).

[petevdp]

Okay, I'll give that a try then, thanks!

[brapifra]

I see an open PR for this. Any updates? @petevdp @SimenB
I'd love to see this merged soon 🙂

[SimenB]

#10713

[github-actions]

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