add initial tox.ini

[jakkdl]

I started out on a tox.ini because it's handy to have; it's not complete enough to close #3170, but it should be sufficient for #2699 once the CI is updated to use it.

• there's a bunch missing to completely get rid of ci.sh, I almost suspect we might need nox for that not to be a nightmare.
• I probably prefer having this in pyproject.toml, which tox now supports natively, but being so used to tox.ini I didn't realize this until most of the file was written.
• I haven't switched over anything in ci.yml to actually use this. We'd probably want https://github.com/tox-dev/tox-gh or https://github.com/ymyzk/tox-gh-actions to do that properly

everybody's very welcome to push commits to this PR, but I don't think we should block merging it until the tox/nox config is perfect (leaving that for followup PRs) Cause I Wanna Use It ™️

[jakkdl]

ugh, native toml not supporting https://tox.wiki/en/latest/config.html#conditional-settings makes it a non-trivial conversion. I think the way to get around that is with more explicit environments + https://tox.wiki/en/latest/config.html#string-substitution-references; but... that's for another day/person

[jakkdl]

If you review ci.sh with ignoring whitespace: https://github.com/python-trio/trio/pull/3196/files?w=1
you see that it's solely just removing the CHECK_FORMATTING logic.

I propose delaying further CI/ci.sh/tox-gh stuff for future PR's, as that quickly gets very messy.

[CoolCat467]

I think this mostly makes sense, wondering about mypy runs, and I thought there was some sort of tox github actions thing that was useful for some reason the last time I used tox.

[CoolCat467]

Shouldn't this use mypy_annotate?

[webknjaz]

@jakkdl thanks for pinging! Love that it's being worked on. I'll review shortly :)

[webknjaz]

• I probably prefer having this in pyproject.toml

I'd vote for tox.toml since dumping multiple things into one terribly huge config is going to be difficult to maintain.

[webknjaz]

You may want to use tox-uv too. Though, it's okay to omit. Especially in the initial effort.

[webknjaz]

Could you add description = to every env? It should explain what they do and would be printed out via tox l or tox -av.

[webknjaz]

We can also make RTD just call tox in a follow-up. This is what I do these days.

[webknjaz]

These aren't tests, semantically:

Suggested change

	commands =
	cythonize --inplace -X linetrace=True tests/cython/test_cython.pyx
	python --version
	cython --version
	commands_pre =
	python --version
	cython --version
	cythonize --inplace -X linetrace=True tests/cython/test_cython.pyx
	commands =

[webknjaz]

Let's also add --python-version= in follow-ups.

[webknjaz]

and I thought there was some sort of tox github actions thing that was useful for some reason the last time I used tox.

@CoolCat467 there's a plugin: https://github.com/tox-dev/tox-gh. It also demonstrates separating the invocation into preparation and testing. But I think this is something to look into separately, beyond the initial effort. I don't exactly like how the jobs are mixed up right now, but I believe this is out of the scope, so I choose not to start those discussions just yet.

[webknjaz]

I think this is ready to be merged and can be iterated on separately. Though, if you have a minute to accept the commands_pre thing and add descriptions, it'd be nice to include into the scope of this PR.