[Distutils] optional binary compilation under future installation tools

[Chris McDonough]

On Thu, 2012-09-13 at 10:44 +0200, Tarek Ziadé wrote:
> On 9/13/12 10:15 AM, Chris McDonough wrote:
> > Some packages we maintain currently provide largely identical
> > side-by-side implementations of features: one implementation is written
> > in C, the other implementation is written in Python.  The C module is
> > just an optimized version of the Python code.
> >
> > There is logic at module scope within modules in the same package which
> > attempts to import the C version.  If the C version cannot be imported
> > (an ImportError is raised), the logic falls back to importing the Python
> > version:
> >
> > try:
> >      from . import cmodule as module
> > except ImportError
> >      from . import pymodule as module
> >
> > This means that the package can be used if the C implementation is
> > compiled or not.  It will run more slowly, but that's OK in lots of
> > cases.
> >
> > In our setup.py for these kinds of distributions, we have code which
> > under Py2 uses a setuptools "feature" and under Py3 registers a
> > different kind of build_ext which, at install time, will:
> >
> > - Attempt to compile the C if suitable build tools seem to exist on the
> >    target system.
> >
> > - If suitable build tools don't seem to exist on the target system, will
> >    print a message and continue.
> >
> > How can we support such a feature in the brave new declarative packaging
> > world?
> >
> > - C
> >
> FWIW there's an 'optional' option for the Extension class in Python 2.7 
> in distutils.
> 
> see 
> http://hg.python.org/cpython/file/9b40d018e4cf/Lib/distutils/command/build_ext.py#l458
> 
> If the compilation fails it just warns and continues.
> 
> That option is also present in distutils2, so you can use it in the 
> setup.cfg file.
> 
> Does that work ?

Yep.

- C