Allow 'file:' for tests_require and install_require in setup.cfg

[althonos]

Hi !

Most of the people use a requirements.txt file for managing their dependencies. Unfortunately, setuptools does not support reading from those files for the requirements tags, which means that devs have to either duplicate their requirements file in the install_requires parameter, or not use a requirement file at all. Since setuptools already supports reading some metadata from a file, it should probably be allowed to read those parameters as well.

[jaraco]

What should happen if the requirements.txt includes syntax other than simple lists of requirements (perhaps with environment markers)? Presumably comments could be ignored, but what about options to pip like -i or -e?

Already, the guidance by the python packaging user's guide describes the distinct purposes intended for requirements.txt versus 'install_requires' and similar. By referencing a requirements.txt file for a package's declared minimum required versions, it violates some of the goals of a requirements.txt (showing pinned versions for an environment).

How do we reconcile these challenges?

[techtonik]

Write user stories? I'd just paste requirements spec into setup.py as is.

[jaraco]

I don't see a viable proposal here.

[jianlins]

Put this function in setup.py will do the job:
def parse_requirements(requirements_file):
requirements=open(os.path.join(os.path.dirname(file), requirements_file)).read().split('\n')
requirements=[r.strip() for r in requirements]
requirements=[r for r in requirements if len(r)>0 and not r.startswith('#')]
return requirements