On Tue, May 29, 2012 at 7:41 PM, PJ Eby email@example.com wrote:
I might be confused; I haven't been following the goings-on of late with distutils2. At one point, I thought the plan was not to bless or include dependency-managing installers with the stdlib, or something like that. i.e., I thought the plan wasn't to support or bless full-service tools like buildout, easy_install, or pip, or anything comparable to them.
Right, yeah, the plans in this area were fluid for awhile, but the eventual conclusion was that the stdlib should have a command-line utility capable of installing packages with dependencies. That exists in default branch now; it's called pysetup. It doesn't have nearly all the features of easy_install, buildout, or pip, but it can install packages from an index with deps.
In any case, it still doesn't change the part where it's a good idea to ship a static setup.cfg, with hooks only needing to run on the sdist-building machine, unless they are actually part of the build process. There are use cases for calculated data to be in the initial setup.cfg, where the calculation machinery doesn't need to be on the target (like generating the file list or version from revision control info). So, a setup_requires (or maybe better named "build_requires") would still be helpful, but probably shouldn't be used for setup.cfg stability.
That's not a bad idea for certain kinds of metadata--version/vcs info for example. I like the idea of including a generated "static" setup.cfg in a source dist as a solution to that kind of problem. But that doesn't eliminate the need for setup_hooks (or even more complicated objects like custom commands) in an sdist.
For example, the majority of projects I work on require Numpy to build one or two extension modules. They require hooks to check that the numpy package is importable, and then to use numpy's API to get the paths to the numpy headers and and them to the include_dirs for each extension module that requires them. That's not the only one though--one could have a whole suite of setup_hooks common to a bunch of projects. Custom Compiler classes are a possibility now too.
One could ship a copy of those dependencies with each project, or have some kind of bootstrap script. But to be able to automatically download and add build dependencies to the path (a la setup_requires) would be much nicer. And packaging will have pysetup, so it should be doable. (Having the same capability for test dependencies and doc dependencies would be nice too, but not nearly as important).