Remove setup.cfg in favor of pyproject.toml

[max-sixty]

This is tested, but much of it was me tweaking from an LLM's attempt at the translation, so there may be small issues that aren't picked up in tests (but should be very easy to fix if these come up)

[headtr1ck]

Wanted to do this since ages, haha! Thx :)

[headtr1ck]

This is leftover from your other PR :)

[keewis]

you can also remove setup.py, now that pip (and the wider ecosystem) supports pyproject.toml-based editable installs

[max-sixty]

FYI found another of these and added it to this PR

[max-sixty]

you can also remove setup.py, now that pip (and the wider ecosystem) supports pyproject.toml-based editable installs

Yes, I'm not sure how long we need to wait for this. I'll merge this and we can remove setup.py in a separate PR?

[keewis]

I'd consider editable installs to be development-only, so I don't think we need to wait.

If we did, we would have to wait until we can drop python 3.9, which according to SPEC0 would be pretty soon? If we do count pip=21.3 being released about a week after python 3.9, we'd have to wait another year.

[max-sixty]

If we did, we would have to wait until we can drop python 3.9

Would this mean we can't develop on 3.9?

[keewis]

as far as I remember, we had the rule to support the newest packaging tool version available at the release of the oldest supported python version.

Would this mean we can't develop on 3.9?

once we drop support for a python version, developing on said version wouldn't make too much sense, anyways. I'm not saying that we should immediately drop that version once policy allows it (and I didn't check whether our policy aligns with the SPEC), but this would be one point in favor of doing so earlier

[max-sixty]

Sorry — I had meant — would removing setup.py mean we couldn't develop on python 3.9? (My message was confusing re whether I was referring to us removing setup.py vs. dropping 3.9 support...)

[keewis]

would removing setup.py mean we couldn't develop on python 3.9

as long as you have a version of pip (or any other frontend) new enough to support PEP 660, you should be fine. What I was talking about was backwards compatibility (some people use really old versions of pip), which I don't think is that important for development.

[max-sixty]

as long as you have a version of pip (or any other frontend) new enough to support PEP 660

Super, thanks. Agree!

[mathause]

Nice - thanks! Can we also remove requirements.txt? I think https://github.com/pydata/xarray/network/dependencies also parses toml files.