Enable pep517 builds

[jonathanberthias]

The python ecosystem is slowly deprecating the setup.py file, and moving towards a more flexible build system based on PEP 517. Some tools such as Poetry have decided to enable PEP 517 by default, which means packages which are not compatible and do not provide wheels for every possible architecture cannot be installed (see e.g. #25).

This PR allows pip install --use-pep517 to work by adding a minimal pyproject.toml file.

[CLAassistant]

All committers have signed the CLA.

[ErikBjare]

Also bumping into this issue, would be great to see this merged!

@vineetbansal Plz merge ❤️

[ErikBjare]

I've switched to using qdldl from @jonathanberthias branch and can confirm it works great.

[bendajam]

I would also like this to be merged it would be fantastic!

[vineetbansal]

Sorry for not getting to this sooner. This looks good to me. Thanks @jonathanberthias. @imciner2, @bstellato - any concerns? This is the setup we're using in osqp-python for a little while now as well.

[imciner2]

Adding the pyproject to support pep-517 is good, and my only point is a question: Why do we need to remove the setup_requires from setup.py for this? Will that break any installs that try to use the older setup.py-based toolchain instead of the new pep-517 one?

[jonathanberthias]

Indeed it does not have to be removed. However, the setup_requires keyword is officially deprecated, as is using the setup.py based workflow.
If you want to keep it, I will revert that change.

[vineetbansal]

@imciner2, @jonathanberthias - my recommendation would be to not include it (i.e. keep things as-is). An explicit failure on python setup.py <command> is actually a good indication to the user that they're doing something wrong. It is trivial for a user to update their pip using pip install --upgrade pip in the unlikely scenario that their pip is too old to understand pep517.

[imciner2]

What version of Python/pip was this support added in? My main concern is that QDLDL is built as a scientific/mathematical library, and some users could be on clusters that aren't regularly updated (and that they don't have permissions on). I'm fine adding the parallel build system to modernize it, but I am less sure about intentionally breaking the old build.

[jonathanberthias]

@imciner2 PEP517 support was added in pip 19: https://pip.pypa.io/en/stable/news/#v19-0, which was released in Jan 2019.

[JacobHayes]

I coincidentally made #29 before seeing this PR. That one leaves setup_requires alone if the maintainers want to just go with that (otherwise, feel free to close!)

[vineetbansal]

Sorry for the delay here. If we're going to keep setup_requires to support pre-Jan 2019 versions of pip, I'd propose at least changing the min. required version of setuptools in pyproject.toml to be setuptools>=49.5.0, since that version (correctly) ignores the setup_requires section, so that these build-time dependencies don't end up in the runtime environment.

@jonathanberthias - would you mind putting back the setup_requires and adding the setuptools>=49.5.0 to pyproject.toml? I can merge this in once done.

If I'm missing/misunderstanding any issue here, let me know.

[JacobHayes]

Just adding @vineetbansal's requests as GH suggestions to make it easier to apply

[jonathanberthias]

Thanks for taking care of this @vineetbansal @JacobHayes!

[bperkins24]

I'm not seeing this available on pypi.org, am I missing something?

[vineetbansal]

This is related to issue #23. It may be time to make a new qdldl-python release. Let's discuss it there.