Bug#867104: wanna-build issue with src:perl versioned Provides

[Ralf Treinen <treinen@free.fr>]

On Tue, Jul 04, 2017 at 10:29:35PM +0300, Niko Tyni wrote:
> (dropped some cc's)
> 
> On Tue, Jul 04, 2017 at 09:09:37PM +0200, Ralf Treinen wrote:
> 
> > thanks for having figured that out. I tend to believe that dose is right
> > in this case. Since it is not possible to install at the same
> > time two different versions of the same real package, the same should
> > IMHO hold when one is real and the other virtual. Why should this be
> > possible?
> 
> Well, dpkg and apt allow it for starters.
> 
> The idea with the perl packages is that the src:perl binary packages
> offer an older "stable" version of some modules while a newer version is
> packaged separately and gets installed earlier on the Perl search path
> (so it overrides the src:perl version when installed.)
> 
> This has been the case for ages with the src:perl packages Providing
> an unversioned virtual package. The change here is that the virtual
> package is now versioned, which would simplify lots of dependencies
> that currently read like (for instance)

So, that means that something like

Depends: p (=1), p (=2)

suddenly becomes satisfiable (when there is one real package p and
one virtual package)? Would you also allow to have the packages p
and q installed at the same time, in the following situation:

Package: p
Version: 1
Provides: v (=1)

Package: q
Version: 1
Provides: v (=2)

If yes this seems to me a quite drastic change of the meaning of 
package relations. Has this been discussed somewhere?

-Ralf.