Use pyproject.toml

[jarrodmillman]

This uses pyproject.toml and removes setup.py, .mypi.ini, and ruff.toml. I replicated the previous behavior where setup.py was grabbing optional dependencies from the requirements files using the same system we used in scikit-image (scikit-image/scikit-image#6726 and scikit-image/scikit-image#6763) and numpydoc (numpy/numpydoc#474).

pyproject.toml is autogenerated from the requirements and tools/pyproject.toml.in via python tools/generate_pyproject.toml.py. The pre-commit monitors everything to make sure things don't get out-of-sync.

[dschult]

Nice to have this working! :}

Can you explain why we don't need wheel or setuptools anymore? What is doing the work that replaces them?

Picky nits:

• some places use single quotes ', others use double ", some use both -> pyproject.toml.in lines ~50 and ~100. Does it matter? That is, is toml like python in its treatment of " vs '?
• I found a skimage -> networkx conversion.

[jarrodmillman]

Can you explain why we don't need wheel or setuptools anymore? What is doing the work that replaces them?

In pyproject.toml we have

[build-system]
build-backend = 'setuptools.build_meta'
requires = ['setuptools>=61.2']

Basically, pip 10+ will create a new virtual environment, install setuptools>=61.2, and then build a wheel. setuptools requires wheel, so it will be brought in as well.

If we use --no-build-isolation, we would need to handle the virtual environment and installs ourselves.

There is more detail here https://learn.scientific-python.org/development/guides/packaging_classic/#pep-517518-support-high-priority.

[jarrodmillman]

I think the above means we can simplify things in our CI more (perhaps). I haven't had time to look into it, but was planning to talk to Henry about it soon.

[dschult]

Nice! Thanks! i approve this PR

[rossbar]

LGTM, thanks @jarrodmillman for making this transition. I'm not an expert on PEP517/518 but from my limited understanding I think this makes sense!