Run setup.py install if setup.py egg_info is not supported

[techtonik]

Issue #25 (closed) still contains many comments, as well as question about invalid command egg_info is top 16th about pip on StackOverflow. https://stackoverflow.com/questions/tagged/pip

I'd like to return to suggestion by @vbabiy to download each package and then instead of running egg_info, running install, but add correction to fallback to install only if egg_info is invalid command. Are there any objections?

[pfmoore]

This was already rejected under issue #25. From that issue, "pip ensures that all dependencies can be found, unpacked, and have working setup.py before it installs any of them" and to do that we need to successfully run egg_info.

Your suggestion of a fallback doesn't help, because if we do fall back, we won't install dependencies, which is not acceptable (as it leaves the user with a broken system).

Closing as a duplicate of #25.

[techtonik]

@pfmoore, if the package doesn't support egg_info, it doesn't support dependencies. Why do you insist that it has them? It is a job of package maintainer to add them, not a job of pip to decide that all packages should have at least one dependency.

[dstufft]

We don't meaningfully support anything more than distutils or setuptools currently. Attempting to shoe horn other things into the setup.py script at this point in the game is just going to make things harder and more confusing. Long term the way is with static metadata.

[pfmoore]

As @dstufft says, we support setuptools and distutils at the moment, and we specifically only support dependency resolution via the established mechanisms in those packages.

The issue in #25 was that scipy needed numpy installed in order for its setup.py to run (I don't know if that's still the case). At the moment, neither setuptools nor distutils provide a means to express that dependency so that pip can use it. So that scenario is not supported. End of story.

Future metadata and distribution format standards (Metadata 2.0 and Sdist 2.0) will include means to express such dependencies and pip will be updated to support those means.

In the meantime, we're not going to accept requests for stopgap solutions. It's not as if this is a critical issue anyway. Just manually handle the dependency by running pip install numpy before you run pip install scipy. The scipy docs can make this clear, if they need to.

[techtonik]

@pfmoore please note that although this issue mentions issue #25, it is not about scipy and numpy from that issue, and it is not about dependency resolution either.

[techtonik]

@dstufft it looks like pip supports only setuptools if it insists that every package should mention its dependencies (which distutils doesn't support IIUC),