Bug#964026: libelogind0: `Provides: libsystemd0` causes unrelated packages to fail to build (unmet dependencies)

[Ansgar]

On Thu, 2020-07-02 at 16:34 +0100, Mark Hindley wrote:
> On Thu, Jul 02, 2020 at 04:33:36PM +0200, Thorsten Glaser wrote:
> > On Thu, 2 Jul 2020, Ansgar wrote:
> > > package), so the problem might also be the `Provides: logind` in
> > > libpam-elogind.
> > 
> > Shouldn’t the package dependencies on default-logind | logind
> > handle this?
> 
> Absolutely.

It doesn't as you can see.  In reality dependencies don't work as
simple as "apt will always pick the first choice".

> Nothing you have shown so far demonstrates anything wrong with the
> src:elogind
> dependencies. In fact you have suggested several times that this is an issue
> with apt or whatever dependency resolver the experimental buildd uses.

If you manage to fix this in the dependency resolver that's also fine;
I don't care much how this is fixed, but I believe that packages should
be buildable without manual intervention.

In general satisfying dependencies seems to be a complicated problem
and resolvers will sometimes not be able to find a desired solution.
Changing dependencies in those cases is fine and (as far as I know) has
been done previously for other cases.

> Can you provide information from the resolver to show how it is
> coming to its incorrect decision?

I'm not an expert on dependency resolvers, no.

Ansgar