[Zope-PAS] Re: Eggification redux

[Jim Fulton]

On Sep 25, 2007, at 9:53 AM, Tres Seaver wrote:

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> Jim Fulton wrote:
>
>>>>> * When package A depends on Y and package B also depends on Y,
>>>>> but with some version restrictions, buidout will first try to get
>>>>> the newest version of Y when installing A. But then when
>>>>> installing B, it is likely that it has to get a different version
>>>>> of Y. The result is a version conflict. This could also easily be
>>>>> fixed with a working set that dictates which versions would be
>>>>> used from the beginning.
>>>> IN the long run, this would be better served by a better algorithm
>>>> for constructing setuptools working sets.
>>> ... which would require having access to the dependency data before
>>> installation.
>>
>> No, not really, at least not in buildout's case.  It's really not
>> that big a deal to download a distribution that you ultimately don't
>> use.
>
> If we can keep setuptools from prematurely installing downloaded eggs,
> sure;

I'm not sure what you are saying.  I maintain that downloading eggs  
you don't use is not that big a deal. Avoiding this is just an  
optimization.

> at the moment, it is trivial to get setuptools into a "false
> conflict" situaltion, because it processes dependencies incrementally,
> rather than solving the "transitive closure" of the graph before
> attempting to install anything.

Sure, but this doesn't have anything to do with whether you download  
or not.  It may be a consequence of the fact that setuptools tries to  
hard to figure out what to use without downloading enough. There is a  
similar problem with extras.

>
>> I agree it might be better if the index made dependency data
>>> available.
>
> Not exposing the dependency information in the index seems like a
> missing-feature-is-really-a-bug to me.

Likely.   A problem is that there are 2 sigs when there really ought  
to be one.  The distutils sig isn't demanding enough of the catalog- 
sig for changes to the index and the catalog-sig is somewhat  
grudglingly responsive.  Some of this has to do with the fact that  
people who want catalog features really ought to help with  
implementation, but people who want the features don't have the time  
to learn the catalog app enough to enhance it.  It would be nice if  
one of us was willing to become a catalog contributor so we could get  
some things done we need. Not it! :)

Jim

--
Jim Fulton
Zope Corporation