[Distutils] Adding Provides-Extra as an edit to PEP 345

[Daniel Holth]

>> I expect to see a lot of bugs in packages that require some of their
>> build-time dependencies at run time.
>
> Maybe, but wouldn't that be the developer's problem?  setup_requires
> has the same issue--it does not install the setup requirements into
> site-packages.  Instead it just does an egg install into the source
> directory and activates it on the path.  Outside of future setup.py
> runs, the setup_requires distributions are not available (you would
> have to add them to install_requires too if you need them at runtime).

OK, it sounds like this "bug" has been mostly anticipated and taken
care of already.

> Under a scheme like this one would have to list that dependency under
> Requires-Dist twice: with and without the 'extra' marker.  I might
> still prefer extending the metadata format to add a
> Setup-Requires-Dist or the like.

I don't follow. Does anyone build/install packages without also first
installing the run-time requirements? Surely Setup-Requires-Dist would
have exactly the same problem. It seems like two ways to say exactly
the same thing.

Let's just try to focus on getting Metadata 1.2 out the door and
implemented before its 8th birthday, preferably during Julython... The
only thing I need is to be able to represent the wildly popular
"extras" feature in METADATA to benefit from PEP 345 and 376 without
rewriting thousands of Python packages. That is all. Save the debate
about reserved "extra" names for setup / build / test / doc
dependencies for Metadata 1.3.