Re: Should we allow packages to depend on packages with lower priority values?

[Jakob Bohm <jbj@image.dk>]

On Fri, Dec 19, 2003 at 04:18:14PM +1000, Anthony Towns wrote:
> On Mon, Dec 08, 2003 at 03:17:19PM +0100, Marc Haber wrote:
> > Let A and B both be packages that provide virtual package C. A is the
> > default C in Debian, and is therefore Priority: important. A depends
> > on E and F, which must be Priority: important as well, as required by
> > current Policy.
> >
> > Now let's look at a system where the local administrator has decided
> > to use B instead of A. 
> 
> 
> > Since E and F are Priority: important, dselect
> > happily proceeds to install E and F on the system, even if they are
> > not needed since the system in question uses B instead of A.
> 
> Now let's consider what happens if they've already installed the system,
> with A, and hence E and F. The run dselect, or apt-get, or even dpkg, and
> install B, remove A and are left with B, E and F.
> 
> If that's not what's desired, your dependencies are wrong.
> 

Since any policy change now would probably be for sarge+1, let's
assume aptitude or another interface with a notion of "installed
only due to dependencies".  With this I think the current
behavior is (not experimentally verified though):

(To make the examples clearer, imagine A=exim, B=nullmailer, 
E=cron, F=libldap2, this was a real example in woody).

Initial system install, user unselects package A during system
bootstrapping: If E and F are tagged "Important" they continue
to be installed (as useless, non-conflicting cruft), because all
the Important packages are initially marked as "Install on own
merit".  If E and F are tagged optional or lower, they were only
marked as "Install due to dependency" and get implicitly
unselected too, unless needed by other packages.

Manual, post-install change, user requests removal of A and
install of B: If E and F are tagged "Important" they continue to
be installed (as useless, non-conflicting cruft), because all
the Important packages were initially marked as "Install on own
merit" during system install. If E and F are tagged optional or
lower, they were only marked as "Install due to dependency" and
get implicitly removed too, unless needed by other packages.

So I think the proposer may have a valid point that upping
package priorities to Standard or higher just because they are
needed by packages above that line cause unnecessary cruft on
end-user systems.


Merry Xmas, Happy Solstice, Glaedelig Jul

Jakob

-- 
This message is hastily written, please ignore any unpleasant wordings,
do not consider it a binding commitment, even if its phrasing may
indicate so. Its contents may be deliberately or accidentally untrue.
Trademarks and other things belong to their owners, if any.