[Catalog-sig] PEP 345 Update

[M.-A. Lemburg]

Alexis Métaireau wrote:
>  Le 08/24/2010 05:12 PM, M.-A. Lemburg a écrit :
>> I do see a problem with such a general purpose "conflicts" field,
>> regardless of what the use case is. If the installer prevents
>> packages from being installed by means of defining such
>> a "conflicts" field, this can be used to externally make
>> package sets incompatible, e.g. a package of
>> framework 1 could effectively prevent the installation of
>> a competing framework 2, even though they both can live
>> happily side-by-side on sys.path. And there's nothing the
>> authors of framework 2 could do about this.
> of course, we can force the installation in installers with --force, in
> such a case, but that's not why the "conflict" field is. Eg. If both can
> leave together, they're not conflicting :)

I guess that's where part of the misunderstanding originates:
the type of conflict can be many things and may well only
show up in certain applications using the packages, but
not necessarily all of them.

At the very least, there should be an extra field "Conflict-Description"
which describes the type of conflict to the user and then lets him or
her decide whether the conflict is a problem or not for the intended
use.

I have a feeling that the introduction of this field originated
from some application space problem that you're trying to fix
at the package level.

Also note that a the use cases you and others have mentioned can
easily be solved using meta-packages and dependencies on these or
by the installer checking whether there are module name or
file conflicts (i.e. two packages wanting to install the same
module or create the same file).

-- 
Marc-Andre Lemburg
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