[Distutils] Reverse dependencies

[Jim Fulton]

FWIW, I expect to have to implement this for buildout at some point.   
I don't plan to do it until it becomes a priority. :)

WRT platform, I see this as an anti-solution.  Fortunately, it looks  
like it has already been dismissed. :)  The reason I see this as an  
anti-solution is that we already have a platform, namely Python 2.4,  
that might be better treated as a dependency.  For example, there  
isn't a way, AFAIK, to state Python version requirements for source  
releases.  I think it might be cleaner if things like Python version  
and maybe even size of unicode characters could be handled using the  
dependency mechanism.

Jim

On May 13, 2007, at 2:10 PM, Phillip J. Eby wrote:

> At 06:11 PM 5/13/2007 +0100, Martin Aspeli wrote:
>> Phillip J. Eby wrote:
>>> At 05:00 PM 5/13/2007 +0100, Martin Aspeli wrote:
>>>> But is there any support for such declarative "reverse"  
>>>> dependencies?
>>>
>>> Sort of, in a very limited way.  You'll get a version compatibility
>>> error if you depend on say, Plone<3 and your dependency depends on
>>> Plone>=3.1, for example.  But there's no backtracking to resolve
>>> this, so the minute it happens your installation is basically dead
>>> until you get rid of the problematic package.
>>
>> Comforting. :-)
>>
>> Do you think it'd be a useful feature? I realise it may not be
>> immediately trivial to add. ;)
>
> No kidding.  I believe it's potentially NP-complete, which is why I
> only implemented a non-backtracking version that always goes for the
> highest installed version of each package.
>
> If somebody else wants to take a look at designing a backtracking
> algorithm, take a look at the WorkingSet.resolve() method in  
> pkg_resources.
>
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