PEP 517 build options

[bharel]

What's the problem this feature will solve?

I'm trying to restrict a python wheel to the CPython implementation, using setup.cfg and PEP 517/518:

pip wheel --build-option python-tag=cp3 .

Unfortunately, as of now, it's not possible.
I can't specify an implementation inside a setup.cfg, nor in pyproject.toml.
I also can't pass parameters to pip wheel as, to my understanding, PEP 517 does not guarantee setuptools to be the backend.

Describe the solution you'd like

It's either a change in pip to support passing build options to an unknown backend, or a change in setuptools to support them in setup.cfg.

As a real world use-case, I have packages relevant only to CPython (latest one deals with the garbage collector).

Alternative Solutions

The only solution as of now is to abandon PEP 517, and use the deprecated setup.py.

[pfmoore]

setup.py isn't deprecated, it's how you configure setuptools. If you set the relevant options in setup.py, and build with pip as normal, pip will work fine.

PEP 517 allows for different backends, but any one project will define the specific backend that they use. So you can happily use setuptools mechanisms, and don't need to worry that someone will randomly try to build your project with a different backend...

[bharel]

I might have misunderstood, but reading the setuptools documentation, one may believe setup.py is being phased off.

[pfmoore]

Running setup.py directly (rather than via the PEP 517 backend using pip) may be something they want to phase out, but they aren't going to just drop functionality so there should be a way to get the behaviour you want even then. But that's something you should discuss with them, it's not a pip issue.

[bharel]

Alright, thank you very much and sorry for posting in the wrong forum :-)
I still do think build options should pass to the backend, much like --config-setting in pypa's build.

[sbidoul]

Adding PEP 517 config settings support in pip is tracked in #5771.