Add a separate "build_cython" command to setup.py

[embray]

This is a follow-on to #21600. It adds a new cythonize command to the setup.py, and moves most of the logic for running cythonize() (previously in the customized build_ext) command, into this new command.

The new cythonize command is run always from build_ext anyways, but this has a couple advantages:

1. It is possible to run just cythonize, without compiling extension modules. This maybe isn't that common, but can be useful for development, especially when testing issues with Cython itself. It will also be useful for generating source distributions, where we might want to ship Cythonized sources in the source tarball, and hence would need to generate them as part of the process of building the tarball (without necessarily compiling).

This also allows passing options directly from the command-line to cythonize. This isn't much taken advantage of currently but the possibility is there.

2. Code is clearer and more modular. Specific details for compiling cython code are kept separate from details for compiling C/C++ code.

See also upstream discussion of a "generic" implementation: cython/cython#1514

Upstream: Reported upstream. Developers acknowledge bug.

CC: @mkoeppe

Component: build

Keywords: cython distutils

Author: Erik Bray

Branch/Commit: a049f2d

Reviewer: Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/21682

[embray]

comment:1

I have a few other to-do issues in this code, but they're not essential. Not sure if they should be worried about for now, or in a follow-up issue if this code is accepted.

[jdemeyer]

comment:2

I suggest that you first discuss this with upstream cython.

[sagetrac-git]

Changed commit from 80955e5 to 487d66a

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

487d66a

Add a new 'cythonize' command to setup.py to logically separate out the cythonization step.

[embray]

comment:4

Rebased--I agree this could also be worth bringing upstream in some form, but do you have any other comments?

[jdemeyer]

comment:6

Replying to @embray:

do you have any other comments?

It would be better to separate the Sage-specific parts from the general code which could be upstreamed.

[jdemeyer]

Changed dependencies from #21600 to none

[jdemeyer]

comment:8

Bikeshed: since all build commands start with build, wouldn't this command better be called build_cython or something like that?

[jdemeyer]

comment:9

Why did you change

os.environ.get('SAGE_DEBUG', None) != 'no'

to

os.environ.get('SAGE_DEBUG', 'no') != 'no'