RPM Soft dependencies (Was: Re: Agenda for the 2009-05-26 Packaging Committee meeting)

[Jussi Lehtola]

On Sun, 2009-05-31 at 11:29 +0200, Mathieu Bridon (bochecha) wrote:
> > users may not want those features. A soft dependency covers this
> > situation pretty perfectly; by default you get the extra dependencies
> > installed so the features will be available, but if you're someone who
> > needs to optimize disk space or number of installed packages you'll have
> > configured urpmi not to install soft dependencies so you won't get them,
> > and if you didn't do that but you later decide to remove one of the soft
> > deps, you can. I consider this a significant win, the package would be
> > objectively less good without this.
> 
> How do you know _later_ which installed packages could be removed as
> they only came via soft dependencies ?
> 
> « package-cleanup --soft-leaves » or something like that ?

Is this possible now even with hard dependencies? If I install package A
that requires B and C, but decide I don't like it so I remove package A,
B and C still stay on my system.

For me the situation sounds quite clear: you have a switch somewhere
which controls if soft dependencies are treated as hard dependencies or
ignored. If you install some package that has soft dependencies and the
switch is on, everything is pulled in. The same thing in case a package
is updated and it has unsatisfied soft dependencies.

If the switch is off all soft dependencies are ignored both in install
and update. On a minimalist system one could have those flags off for
everything else than, say httpd.

A two-tier system (Recommends, Suggests) could also be treated this way:
you could have a treat-recommends-as-requires flag and a
treat-suggestions-as-requires flag. This would enable a more
fine-grained control.
-- 
Jussi Lehtola
Fedora Project Contributor
jussilehtola at fedoraproject.org