[Distutils] distlib - installer support vs runtime support

[Daniel Holth]

The pkg_resources script entry point is there so the right eggs can be
added to sys.path based on solving dependencies for the invoked package.

On Mar 10, 2013 7:30 AM, "Paul Moore" <p.f.moore at gmail.com> wrote:
>
> On 10 March 2013 00:15, Vinay Sajip <vinay_sajip at yahoo.co.uk> wrote:
> > Paul Moore <p.f.moore <at> gmail.com> writes:
> >
> >> Would it be worth considering splitting distlib into two separate
> >> parts - one that is intended solely for writers of installers and
> >> similar tools, and another for "runtime support" functions that end
> >> users would use? It may not be a practical thing to achieve, but it
> >> would be worth at least understanding the trade-offs involved.
> >
> > While this could be done, it would not exactly be elegant, and IMO it
would be
> > the wrong way to address the valid concerns you mention. It would make
more
> > sense for pip to *contain* a specific version of distlib for its use
(e.g. as a
> > .zip) so that it never worries about conflicts with another copy. This
is the
> > approach that Django takes and it seems to work reasonably well for that
> > project.
>
> Thanks for the comments. It looks like pip will indeed contain a copy
> of distlib, at least for now. And I think you're right, that is the
> best solution there.
>
> My other interest was with regard to virtualenv. Here, the particular
> "runtime support" issue that bothers me is the way that setuptools
> wrapper scripts use entry points. As a result, something like
> nosetests.exe will not work without setuptools being present, simply
> because it looks up the code to run using the entry point mechanisms
> (the actual code itself does not need setuptools). So virtualenv
> pretty much *has* to preinstall setuptools (or at least
> pkg_resources), as pip uses exe-wrappers, and those won't use an
> embedded copy.
>
> But looking at the code generated by distlib's script wrappers, I see
> that it does not use the exports functionality of distlib, and as a
> result distlib-generated wrappers can be used without distlib being
> present. So my apologies here - it looks like my concern was
> unfounded.
>
> Paul.
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