[Python-Dev] PEP 365 (Adding the pkg_resources module)

[Guido van Rossum]

On Mon, Mar 17, 2008 at 1:45 PM, Phillip J. Eby <pje at telecommunity.com> wrote:
> At 12:59 PM 3/17/2008 -0500, Guido van Rossum wrote:
>  >On Mon, Mar 17, 2008 at 12:45 PM, Phillip J. Eby
>  ><pje at telecommunity.com> wrote:
>  > > At 12:17 PM 3/17/2008 -0500, Guido van Rossum wrote:
>  > >  >There will be no egg support in the standard library.
>  > >
>  > >  Are there any qualifications on that statement, or is this in the
>  > >  same category as "from __future__ import braces"?
>  >
>  >IIUC eggs are a method of package management that includes support for
>  >dependencies, multiple versions, and C extensions in zip files, as
>  >well as conventions for naming these and for encoding metadata (e.g.
>  >how to find out the version or the dependencies). This whole set of
>  >conventions is IMO too much to include into the stdlib ATM -- if only
>  >because it has proved controversial in the past. Maybe a few years
>  >from now it will be no longer controversial and then my objections
>  >will disappear.
>
>  So, does this mean that the bootstrap tool must not use eggs?

Correct.

>  That
>  seems a little bit odd, in that setuptools will at least need its
>  .egg-info directory to get installed, and all of the people who'll be
>  using this initially will be using it precisely in order to have
>  support for eggs...

I'm okay if setuptools, once it's been installed, runs some setup code
that creates the .egg-info directory and whatever else. This means I'm
also okay with the bootstrap module finding and invoking that setup
code. But I'm *not* okay with building any kind of egg management into
the bootstrap module. The bootstrap module must be be neutral w.r.t.
the package management style.

>  So, it might be simpler all around to just clear up the
>  "controversy".  To the best of my recollection, only MAL and MvL have
>  ever objected on Python-Dev to the idea of supporting eggs.

You can add my name to the list. I've heard plenty of people speak
highly of eggs, but I've *also* heard from plenty of people (besides
MAL and MvL) who have serious difficulties with the concept of eggs. I
have certainly personally encountered plenty of situations where I
wasn't able to complete an egg-based install because some dependency
was broken (e.g. not available for the Python version I was using).

>  Note: I'm specifically segregating "egg support" from the topic of
>  including setuptools or easy_install in the stdlib directly.  There
>  are many legitimate reservations and open questions about the latter,
>  including availability of volunteer support, choice of defaults,
>  whether to replace distutils with setuptools, etc. etc.  I recognize
>  and respect the validity of those issues, which is precisely why I
>  withdrew setuptools from inclusion in Python 2.5.
>
>  However, regarding support for eggs, my understanding is that there
>  were only two objections to eggs -- even at the time of the 2.5
>  setuptools discussions.  And even though MvL objects to the idea of
>  eggs in *principle*, I didn't read his recent posts as objecting to
>  having the bootstrap tool download and install eggs in
>  *practice*.  (Although I hope he will clarify that stance one way or
>  the other.)

You can do it in two stages. The bootstrap can download and install
egg support, even though the bootstrap itself knows nothing about
eggs. Then another bootstrap can download and install eggs.

>  That leaves MAL, whose objections to PEP 365 centered on the API (he
>  said he was "+1 on the concepts being added to the stdlib, -1 on
>  adding the module in its current state").  Among other concerns, he
>  wanted pkg_resources to be split into pkgutil and a new "egglib"
>  module.  I don't have a problem with this in principle, if there were
>  a pkg_resources module that reconstituted the merged API.  (But there
>  are some practical problems with that approach, such as trying to
>  split namespace package support between two theoretically-unrelated modules.)

Well, you've heard my position now.

>  I would guess, however, that MAL's issues with the pkg_resources API
>  would not apply to a bootstrap module whose sole purpose was to
>  download eggs and put them on sys.path.  Or, perhaps he would object
>  *more*, I don't know.  We could certainly ask him, though.  :)

No need. I object to this myself.

>  So, was there anyone else you were counting towards
>  "controversy"?  The only other person I recall objecting to
>  setuptools in any way on Python-Dev was effbot, and IIUC his
>  objections were practical/administrative re: supporting easy_install
>  and setuptools, not to the idea of .egg support in general.
>
>  In summary, I think the controversy on Python-Dev regarding .egg
>  support has actually been over for some time now.

Not really.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)