Specfile: Provide default generated code in a separate directory about silx

[PiRK]

I can see two simple solutions.

The simplest, which solves only the problem of git complaining, is to put specfile.c in .gitignore. Whenever a change is made to the .pyx file, one has to remember to do a git add --force silx/io/specfile/specfile.c after the file has been regenerated. This solution has the advantage of not adding any line of code to the setup.py and not changing the current behavior of setup.py.

The second solution is to also add the auto-generated file to .gitignore, then to make a copy of it to a file (for instance specfile.c.in) that will not be ignored, and to add code to the setup.py to copy specfile.c.in to specfile.c before compiling unless the command line --force-cython is specified when running setup.py. This adds a manual copy step and makes setup.py more complex. The check_cython() would have to be changed in the general setup.py: --no-cython, fake_cythonize() and os.environ["WITH_CYTHON"] = "False" should become the default behavior.

This second option only makes sense if we don't trust Cython on the user computer to generate proper .c files.

[vasole]

The first solution still overwrites the supplied reference file.

The second solution serves to check if something was wrong at the
building end with, for instance, a buggy cython or for speeding up things.

I am full for copying/renaming a supplied file and not just adding it to
the list of ignored files.

[PiRK]

I worked on the issue, and found that if we want to go down that road, the required steps would be:

• supply a default file, either in a different folder than the pyx file, or with a different name than the cython-generated file (e.g silx/io/specfile.c.in)
• add this file to MANIFEST.in
• in the local silx/io/setup.py, if os.environ["WITH_CYTHON"]=="False", copy and rename the supplied file to wherever the compiler expects it to be (e.g silx/io/specfile.c)
• in the general setup.py, move check_cython() before configuration(), so that the environment variable WITH_CYTHON is set before importing the local setup.py
• optionally: remove the cython-generated C file from the repository (delete and add a line to .gitignore)

This solution seems to work on all tested platforms on my development branch https://github.com/PiRK/silx/tree/nocython

[vasole]

Ok, from the enhancement the only thing that is going to remain seems to be this:

• in the general setup.py, move check_cython() before configuration(), so that the environment variable WITH_CYTHON is set before importing the local setup.py

that I think it was already fixed by #73