Carl Meyer
already satisfied. In pip this happens here: https://github.com/pypa/pip/blob/develop/pip/req.py#L1091
More generally, I wouldn't really recommend pip's dependency resolution logic as a model for new Python code in this area. There are some not uncommon cases that it handles poorly; see https://github.com/pypa/pip/issues/174 and http://bugs.python.org/issue8927. (To be fair to pip, these cases aren't trivial when you have to download and unpack an sdist before you can
Thanks for the pointers.
find out anything about its dependencies, but I'd hope that with the new metadata PEPs Python packaging code could get a bit smarter in this area.)
AFAICT, the proposed metadata PEP changes don't offer the same requirement granularity as setuptools / distribute (for example, 'Requires-Dist' as against 'install_requires', 'setup_requires', 'test_requires'). Anyway, I'll take a look at the issue you mentioned and see how the dependency code in distlib stacks up. Currently, it keeps the requirements distinct for 'install', 'setup' and 'test'. The distinctions seem reasonable in theory, though I'm not sure how useful they are in practice. In the case I was quoting, the circular dependency wasn't being treated as any kind of conflict - I just came across cycles when testing topological sorting of dependency graphs, and was curious about them. Regards, Vinay Sajip