fix: Fix usage of excludeAfterRemap not to set the coverage always to 100

[prantlf]

Do not use the excludePath callback. Remove the excluded sources at the end, after all coverage parts have been merged. This might be a problem in v8-to-istanbul, because istanbul-lib-coverage doesn't offer a method to filter the coverage data at the end.

Attempts to fix #462

Checklist

• [x] npm test, tests passing
• [x] npm run test:snap (to update the snapshot)
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added

[tbo]

This fixes the issue for me. @bcoe is there any chance to get this fix merged? Or is there another workaround?

[bcoe]

Any chance you could add a test?

[timokoessler]

Unfortunately, I cannot use c8 because of the problem. Is there a chance to merge this pull request anyway?

[bcoe]

@timokoessler, @tbo, I would need to see a failing test to be able to land this (I would be very appreciative of a PR that just adds the failing test 👏

@prantlf has provided a repository with a reproduction, so I can use this as a starting point. I'll do my best to start putting a bit more work into this library again, and it seems like this bug should be high up the list of things to fix.