Conditional setup_requires dependencies in setup.py

Question

Is there any way to tell pip to skip some setup_requires dependencies when not needed?

In my scenario, I have pytest-runner declared as a setup dependency (which is used to execute tests) in my setup.py. When I try to install my package (I.e: pip install my-package.tar.gz) it downloads pytest-runner or it fails it is not available (*).

In setup.py I have:

...
setup_requires=['pytest-runner', 'flake8']
...

I would like to tell setup.py only to use pytest-runner only when executing tests. Is that possible?

As @deceze suggested, this declaration will work:

setup_requires=['pytest-runner', 'flake8'] if 'test' in sys.argv else []

But I don't want to add logic to setup.py.

(*) The environment is very restricted, that's why downloading a dependency is a roadblock.

Answer 1

It makes sense to declare that as an extra:

setup(
    ...,
    extras_require=dict(
        tests=[
            'pytest-runner'
        ]
    )
)

You specifically install that with pip install my-package[tests].

As an alternative: setup.py is a fully functional Python program… if you can detect your environment somehow, you can dynamically decide whether to add certain dependencies to the requires list or not.

Answer 2

rwt (Run With This) seems to be the preferred way of doing this.

It provides on-demand dependency resolution, making packages available for the duration of an interpreter session. One of its aimed scenarios is: test runners.

After installing rwt (*), you can load setup.py commands from pytest-runner module executing:

rwt pytest-runner -- setup.py test

or

python -m rwt pytest-runner -- setup.py test

(*) You still have to install an unrequired dependency (i.e: rwt), but it seems to have less impact than installing others.