[Cython] Cannot cythonize subclasses of setuptools.extension._Extension

[Matthew Brett]

On Thu, Apr 14, 2016 at 6:08 AM, Erik Bray <erik.m.bray at gmail.com> wrote:
> On Wed, Apr 13, 2016 at 9:35 PM, Manuel Nuno Melo
> <manuel.nuno.melo at gmail.com> wrote:
>> Hello devs,
>>
>> I'm developing the setup.py for a scientific package, MDAnalysis (see PR
>> #799). We depend on distutils and setuptool. Namely, we use
>> setuptools.extension.Extension class for our extensions.
>>
>> Some older versions of setuptools (<18.0) do filename cythonization
>> themselves upon initialization of the Extension object.
>>
>> Because we want to control name cythonization ourselves I try to directly
>> use distutils.extension.Extension, which has none of setuptools'
>> cythonization. However, this doesn't work because setuptools patches
>> distutils, so that distutils.extension.Extension effectively becomes
>> setuptools.extension.Extension.
>
> I'm wondering what it is specifically you need to do in your
> subclass--might it still be possible to do with a subclass of the
> setuptools Extension?  Not saying I disagree with the overall idea,
> but I also wonder if there isn't a better way.

I know this is a terrible and ugly hack, but the projects I work in
have a 'fake_pyrex' directory, that fools setuptools into thinking
that 'pyrex' is installed, and therefore prevents it from doing the
.pyx -> .c filename conversions in the extension:

https://github.com/regreg/regreg/blob/master/setup.py#L33

Cheers,

Matthew