Fix tox_root propagation to work_dir

[Tbruno25]

This applies a fix for issue #2933 where work_dir was not accurately including the current tox_root during test runs

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• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[kdestin]

Ah, I probably should've mentioned in the issue that I was working on this.

Here's what I have so far: c037e62...kdestin:tox:2d2f0d54922e126a275fec4ecec805ebdcae67de

Let me know if you'd like me to open a PR onto your branch, to incorporate these changes.

---

The only notable differences are:

• I just ripped out the true branch of

   (conf.work_dir if conf.work_dir is not None else cast(Path, self["tox_root"])) / ".tox"

  I may be wrong, but my understanding of the control flow is that the conf.work_dir can never actually be None. In Config.make, it's always set to a non-None value:

  tox/src/tox/config/main.py

  Lines 95 to 96 in a4be5d8

  	root: Path = source.path.parent if parsed.root_dir is None else parsed.root_dir
  	work_dir: Path = source.path.parent if parsed.work_dir is None else parsed.work_dir

  And the true branch doesn't seem like it's needed:

  • The default case gets handled by returning case(Path, self["tox_root"])) / ".tox"
  • The case when work_dir is set by --workdir is handled here:

  tox/src/tox/config/sets.py

  Lines 196 to 197 in a4be5d8

  	def work_dir_post_process(value: Path) -> Path:
  	return self._conf.work_dir if self._conf.options.work_dir else value

• I wrote tests in tests/test_run.py (instead of tests/test_main.py), since there was already a test for --workdir there which would've been similar to the test of --root.

• I believe I have some fixes for some of your test failures

[gaborbernat]

CI is failing.

[Tbruno25]

Let me know if you'd like me to open a PR onto your branch, to incorporate these changes.

Let's merge it in!

I may be wrong, but my understanding of the control flow is that the conf.work_dir can never actually be None. In Config.make, it's always set to a non-None value:
...

• The default case gets handled by returning case(Path, self["tox_root"])) / ".tox"
• The case when work_dir is set by --workdir is handled here:

Agree with your conclusion.

tox/src/tox/config/sets.py

Lines 196 to 197 in a4be5d8

	def work_dir_post_process(value: Path) -> Path:
	return self._conf.work_dir if self._conf.options.work_dir else value

• I wrote tests in tests/test_run.py (instead of tests/test_main.py), since there was already a test for --workdir there which would've been similar to the test of --root.
• I believe I have some fixes for some of your test failures

I was really hoping to avoid altering existing tests which is why I was "guess and checking" with the different fixes. If you've already re-worked these then even more reason to pull it in 👍

[Tbruno25]

CI is failing.

Should be all set thanks to @kdestin 🚀