[Distutils] PEP 517 again

[Chris Barker]

On Thu, Aug 31, 2017 at 11:03 AM, Nathaniel Smith <njs at pobox.com> wrote:

> > Surely the build system should know how to correctly name the wheel it
> builds.
>
> It's probably worth mentioning the specific problem that motivated pip
> to start doing this.
>
> It used to be standard, and is still quite common, for setup.py
> scripts to contain stuff like:
>
>     install_requires = [...]
>     if sys.version_info < (3, 4):
>         install_requires += [...]
>     if platform.python_implementation() == "PyPy":
>         install_requires += [...]
>
>     setup(..., install_requires=install_requires)
>
> This kind of logic in setup.py worked fine in the old days when all
> you did was 'setup.py install', but then wheels came along


And indeed, setuptools originally used easy_install, which was part of
setuptools...

and
> retroactively turned lots of setup.py scripts from working into
> broken. The problem is that with this kind of setup.py,
>


> But it will take a while for existing setup.py files transition to
> using those, and in the mean time pip can't assume that a random wheel
> generated by 'setup.py bdist_wheel' has accurate Python tags.
>

This was my original point -- I understand that we want "pip install" to
continue to work for, hopefully, everything it works for now.

But I do think we should be clear about what is a hack for backward
compatibility, and what is part of the designed functionality.

Sorry to be poking at all this from the fringes (Not having been all that
involved in a very long discussion), it's just that the whole

distutils--setuptools--pip--distribute--setuptools--pip

stack has a LOT of legacy cruft, and I'm  concerned that the efforts for
backward compatibility may end up leading us to another poorly de-coupled
design.


> Hopefully new legacy-free backends will get this right from the start.
>

exactly -- let's keep the "backward compatibility hack" labels clear!

-CHB


-- 

Christopher Barker, Ph.D.
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