Hint at next step, during install, when wheel building fails

[pradyunsg]

ref: https://stackoverflow.com/questions/53204916/what-is-the-meaning-of-failed-building-wheel-for-x-in-pip-install

When pip fails to build a wheel, the message is a little mysterious for the users. It might be a good idea to see how we can enhance that to be "better".

Note that pip wheel uses the same code, so we should consider that here as well.

[cjerdonek]

Good call. At the least, maybe a less-ominous sounding beginning than “Failed” could be used so people don’t get the feeling something went horribly wrong (e.g. “Building a wheel didn’t work so ...” maybe also with a “because ....”).

[cjerdonek]

See also the similar (or same?) #6256.

[pradyunsg]

It's similar -- in general I think we can improve our error messaging here.

[ei8fdb]

@pradyunsg Is this still an issue? I tried to replicate it just now and got:

Successfully built pycparser
Installing collected packages: pycparser
Successfully installed pycparser-2.19

Thanks!

[pradyunsg]

@ei8fdb Yes; the issue is for when the "successfully built" stage fails in your output fails. That failure is fairly system-dependent (eg. missing compiler, missing OS libraries etc).

Currently, pip prints "Failed building wheel for <pkg>" and then proceeds to attempt an install via setup.py install as a fallback. This can result in a successful install (because the fallback worked) and the output containing a message starting with "Failed" -- which is confusing to users (as evidenced by fairly regular traffic on this specific question on StackOverflow).

We can discuss pip's build process in more detail over other media (like a voice/video call) if needed. :)

[nlhkabu]

Perhaps:

Failed building wheel for pycparser
Falling back to attempt install via setup.py.... done
Successfully installed pycparser-2.19

Error:

Failed building wheel for pycparser
Falling back to attempt install via setup.py.... failed
Failed installing pycparser-2.19

@pradyunsg is this accurate? Would something like this be possible?