Use realpath to match transformers

[k15a]

Summary

This will use the realpath to match the transformers in case the path
is a symlink. This will solve an issue where files which are linked by
lerna or npm link are not transformed.

Currently a solution for this problem would be a configuration like:

{
  "transformIgnorePatterns": [
    "<rootDir>/node_modules/"
  ]
}

[cpojer]

This is not passing unit tests.

[SimenB]

Woo, 5000! 🎉

Should this use native realpath, similar to #4730?

In addition to fixing the failing test, I'd love to see a new test for it 🙂

[codecov-io]

Codecov Report

Merging #5000 into master will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5000      +/-   ##
==========================================
- Coverage   60.31%   60.28%   -0.04%     
==========================================
  Files         198      198              
  Lines        6662     6667       +5     
  Branches        4        4              
==========================================
+ Hits         4018     4019       +1     
- Misses       2644     2648       +4

Impacted Files	Coverage Δ
packages/jest-runtime/src/script_transformer.js	84.52% <100%> (-1.98%)	⬇️

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[k15a]

@SimenB This is now using the native realpath implementation similar to #4730. I've seen that there is fs.realpathSync.native which seems more stable than process.binding('fs').realpath() but unfortunately this is not available in graceful-fs and because fs is replaced by graceful-fs I can't use it. This change also fixed all the unit tests.

Not sure how I could test this because I would have to mock process.binding('fs') as well.

[SimenB]

fs.realpathSync.native is only in node 8, so we shouldn't use it yet anyways.

Not sure how I could test this because I would have to mock process.binding('fs') as well.

I don't want you to mock it, I want an integration which uses a symlinked module which shows that the issue you had previously is solved 🙂 (It might not be possible, I don't know for sure)

[k15a]

@SimenB I've added an integration test. Please let me know if I can do anything else.

[SimenB]

Thanks!

[SimenB]

@k15a The test is failing on Windows.

can you send a PR skipping it on windows?

[github-actions]

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