Added --prefer-binary flag.

[DanielShaulov]

Hi,

I ran into #3785, and I need this feature, because c/cpp compilation is cumbersome, so if there is a wheel, even an old one (but still valid for the requirements), i'd rather use it than attempt to compile the source package. I can't use --only-binary :all:, because then python-only package that provide only source distribution won't be installed.
This PR adds the needed feature.

Thanks.

Fixes #3785

[pfmoore]

In principle I like this idea (in some cases, compilation isn't merely cumbersome, it's simply not possible, due to for example lack of a compiler but there's no way for pip to know that in advance). I'd like some tests to be added, to clearly define the expected behaviour. Also, I'm a little concerned about the proliferation of flags here. It might be better to think about the UX across all the options in this area rather than just adding another flag - but that's something we could look at later if needed.

[DanielShaulov]

I added 3 tests which should illustrate the needed behaviour and how it differs from regular and --only-binary :all: behaviour:
test_download_prefer_binary_when_tarball_higher_than_wheel - test the required feature, take the wheel, even if there is a tarball with a higher version.
The other 2 tests (only tarball, and tarball+wheel where the wheel doesn't satisfy requirements) are cases where --prefer-binary does nothing. They are interesting because those are the cases where --only-binary :all: falls short, and they are the reason why prefering binaries is better than forcing binaries.

About the UX issues - the only thing I can come up with to save a flag is --only-binary :prefer: instead of a separate flag. But I think it is way more complex to use and explain an str flag with magics, and using boolean flags is much easier.
If you're talking about some larger UX redesign of all thos flags, which requires breaking the existing ones, than the new flag can be broken as well in the redesign. I will really prefer that this feature doesn't get blocked for such a redesign.

Thanks

[pfmoore]

Agreed, we shouldn't block this on broader questions - I mostly just wanted to add the comment here as a reminder for later.

[pradyunsg]

Maybe make this "> 0.9"?

[pradyunsg]

Is there some reason the test failed on Windows but not on Unix?

[DanielShaulov]

So, it turns out that on windows only, scripttest runs the command with shell=True, because of some bug with PATH handling in subprocess.
So the >=0.9 part just makes the stdout go to a file named 0.9.

I'll try to fix it soon (Maybe I'll just use a requirements file instead of a cli param)

[DanielShaulov]

Fixed :)

[pradyunsg]

LGTM.

If you could update the NEWS fragment, that would be nice (not a blocker). :)

[pradyunsg]

Introduce a new --prefer-binary flag, to prefer older wheels over newer source packages.

[DanielShaulov]

So, can this be merged? (Changed the news fragment)

[pradyunsg]

So, can this be merged? (Changed the news fragment)

Yes.

[desaintmartin]

Would it be possible to have a new version of pip released with (at least) this feature? This is a nice improvement and would be helpful for a lot of people out there.

[pfmoore]

pip 18.0 is due for release this month.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.