On 4 Sep 2007, at 01:21 , Tres Seaver wrote:
Philipp von Weitershausen wrote:
Wichert Akkerman wrote:
The only problem is that distributing grok-0.11.cfg is a bit tedious.
How about if buildout could get it from the web?
How about making it available from an egg, through a hook in egg- info

This is a very good point. So good in fact that I thought of it myself
:) I was already writing the email when your message came in.

Martijn and I discussed the known working set problem over IRC this
afternoon. He brought up a few good points which suggest that the
version data could be associated with the egg:

The approach that I described in my original posting (and which actually
works *today*, as I found out!) has some disadvantages. For instance,
the discoverability and release mechanism of the known working set
configuration file differs a lot from our normal packages. Releasing a package is a well-known routine by now. How and where would we release
the working set configuration file? SVN?

Why not just release a meta-egg with hard-wired dependencies, plus the
scripts required to set up and run the application?  If the other
components are as relaxed as possible about their dependencies, then it
shouldn't matter that the meta-egg nails them down:  it isn't going to
be possilbe to re-use the meta-egg anyway (and I for one wouldn't want
to -- I'd be creating a new environment to run it in).

I think the use case of being able to override a particular version of a package is valid. Let's say I'm on Zope 3.5.0 (meta egg or whatever) and I'd like to get the newest ZODB because it has a really cool feature. Sure, the warranty is void now, but I'd still like to be able to do it *without* having to reproduce all the version dependencies that the meta egg specifies.

Another problem are dependencies and how we'd like to depend on other
working sets. Let's say we made a 'Zope' working set that contained the stable versions of the zope.* packages. It would make sense for grok to
depend on this information. And packages using grok should depend on
that. It'll be complicated to maintain such a chain in separate text
files, especially across version updates. It only seems natural to use
the egg dependency mechanism for this.

Depending on another WS would basically Just Work (TM) if we used egg

It would, but setuptools doesn't allow us to specify "overrides" in case of version conflicts. Perhaps zc.buildout could be taught how. Then I suppose I could settle for using '==' in a meta egg's setup.py.

When EGG-INFO is written, a custom writer will then take this
information and generate 'known_working_versions.txt' or whatever in
EGG-INFO. The only problem is that this custom writer needs to be
installed when setup.py is called to create egg, in other words to
generate the right kind of eggs you'd need to have something installed first. Not sure if this is better than maintaining .egg-info directories
in SVN...

I guess I don't get the usecase for maintaining "known good"
dependencies outside of setup.py (for the "meta" egg).

I don't mind maintaining them in setup.py, but the "install_requires" mechanism is insufficient. Sooner or later you're going to end up with a version conflict.

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