Run linters twice: 1) baseline, 2) current; then show new messages

[akaihola]

Hide linter messages which were already present in the baseline. Track unmodified blocks of code which are moved up or down due to other changes, and match linter messages even though the line number might have changed since the baseline.

Fixes #383 and #380.

• Clean up commits of the branch
• Documentation
• Fix cov_to_lint.py support
• Fix Windows Heisenbug: tests fail unless debug logging is enabled (see [DEBUG] baseline linting with debug logging to troubleshoot Windows #442 for comparison)
• Show also old linter errors which fall on modified lines
• Change log
• Merge Fix Git error output #444
• Rebase
• Self-review
• Peer review

[akaihola]

@PatrickJordanCongenica, you may be interested to try out this branch! It fixes #383 (originally raised by you in #328).

Would you be interested to do a code review as well? Would you accept an invite as a collaborator on the repository so you could be assigned as a reviewer?

I'm going to clean up some commits still though before this is ready for review.

[akaihola]

Hm, let's rethink a bit. With this patch, Darker is only going to show those linter messages which were newly introduced as a result of changes in the code.

But we'd probably want it to also show old linter messages if they happen to fall on modified lines!

[akaihola]

we'd probably want it to also show old linter messages if they happen to fall on modified lines

I believe the patch now does this as well.

[akaihola]

Update: The issue described below was solved in #453.

---

The well-known Python 3.7.2 bug #35797 doesn't explain the test failure on windows-latest, 3.7 (see build #1709) – we're running 3.7.9:

Run actions/setup-python@v4
  with:
    python-version: 3.7
    check-latest: false
    token: ***
    update-environment: true
Installed versions
  Successfully set up CPython (3.7.9)

> os.unlink(fullname)
E PermissionError: [WinError 5] Access is denied:
  'C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\tmp12s99vo_\\test_run_linters_messages_befo1\\.git\\objects
   \\7a\\ea9bf550cfe9c14baf1e82fd65ebf936d81e22'

In a comment to psf/requests-html#249, @ADVEngr had this happen due to failing to provide a proper path for a subprocess:

The displayed error is very misleading, but in my case there was an executable required for a subprocess, and I had only specified the directory containing the executable. Completing the path the the executable solved the issue.

Here in another comment to psf/requests-html#249 is a report from @insanepopeye resembling our case more:

>>> import os
>>> os.chdir(r"C:\Users\Popeye\Desktop\OD\POC\APP\uploads")
>>> test = r"C:\Users\Popeye\Desktop\OD\POC\APP\uploads"
>>> os.remove(test)
Traceback (most recent call last):
File "", line 1, in
os.remove(test)
PermissionError: [WinError 5] Access is denied: 'C:\Users\Popeye\Desktop\OD\POC\APP\uploads'

Could this be because they're trying to remove the current working directory?

In another comment to psf/requests-html#249 @leenjiru pointed to the Stack Overflow question Deleting read-only directory in Python. And like our problem, that question is about rmtree.

This might be a case of Python bug #26660 "tempfile.TemporaryDirectory() cleanup exception if nonwriteable or non-searchable files or directories created".

Maybe it would help to recursively set all created files in the temporary directory read-write at teardown of the git_repo fixture?