Allow --prefer-binary option in requirements file

[stevecj]

• Pip version: 20.0.2

It would be very nice to be able to specify the --prefer-binary option in a requirements file.

Per https://pip.pypa.io/en/stable/reference/pip_install/#requirements-file-format, both --no-binary and --only-binary are supported, but not --prefer-binary. I tried it out to make sure the documentation was accurate, and it is.

ERROR: Invalid requirement: --prefer-binary
pip3: error: no such option: --prefer-binary

[deveshks]

Hi @pradyunsg

Can I take up this issue and file a PR?

I was looking at src.pip._internal.req.req_file.SUPPORTED_OPTIONS and saw that the prefix_binary cmdoptions is missing. I think adding it back should fix this PR.

Also I didn't find good examples on how can the --xx-binary options be used in a requirements file, so I can add it to perhaps as part of that PR.

[pradyunsg]

@deveshks sounds about right, and separate PRs for the semi-related documentation update would be a good idea. :)

[deveshks]

Hi @pradyunsg

I have created #7996 for the issue. Please take a look 😊