On 12/09/2011, at 11:31 PM, Jim Fulton wrote:
On Mon, Sep 12, 2011 at 4:43 AM, Dylan Jay <[email protected]> wrote:
...
My interest in this is the idea that we could get distutils2 and/or
zc.buildout to be able to download regular updates of metadata
including
dependencies, then perhaps those tools could avoid certain kinds of
conflict
errors which are a pain to debug without that information. For
instance, the
current design of zc.buildout means that:
Download Bob. Bob 1.0 requires Fred >= 2.0.
Download Fred 3.0
Download Marry. Marry 1.0 requires Fred < 2.5
Conflict error. Marry 1.0 requires Fred < 2.5 but we already have
Fred 3.0.
If instead we knew in advance of this conflict we could have chosen
to
download Fred 2.4 or at least warned the user there was a potential
conflict
and they should pick a compatible version. In the case of
preinstalled
packages, it could offer to downgrade Fred from 3.0 to 2.4.
The issue here isn't that buildout has to download packages
to get meta data. The problem is that it doesn't backtrack. This is
compounded by fact that when computing and fetching
requirements, it uses a depth-first strategy and doesn't use
information about requirements of other packages in the working
set until too late. There's definitely room for improvement in the
strategy it uses, even short of backtracking.
true but to do backtracking properly could result in downloading many
different available versions of potentially large packages which isn't
so nice.
In any case, allowing buildout to get requirements info before
downloading packages would be a useful optimization, but wouldn't
solve the conflict problem.
yes, backtracking would :) or at least it would solve some of them. Do
you think it's doable even if there's no pypi api to get requirements?
I think this would be a great feature as conflict errors are very
frustrating for new users. They also tend come up in buildout more
than any other tool due to the way to it's normally used and new users
tend to blame buildout for this.
Jim
--
Jim Fulton
http://www.linkedin.com/in/jimfulton
_______________________________________________
Catalog-SIG mailing list
[email protected]
http://mail.python.org/mailman/listinfo/catalog-sig
