Bug#864597: upgrade-reports: jessie -> stretch: gnome fails to upgrade: cycle found while processing triggers

[Guillem Jover <guillem@debian.org>]

Hi!

On Fri, 2017-06-16 at 00:37:20 +0200, gregor herrmann wrote:
> On Thu, 15 Jun 2017 20:31:00 +0000, Niels Thykier wrote:
> > Basically, jessie's verison of desktop-file-utils and shared-mime-info
> > have "-await" triggers (implicit) which will push other packages into a
> > "TRIGGER_PENDING" state.
> >   Once they are in that state, the "damage" is done and those other
> > packages will no longer satisfy dependencies until the trigger has been
> > processed.  Notably, dpkg is unable to /undo/ this state even if the
> > trigger changes from -await to -noawait during the upgrade.
> > 
> >  * If this holds, then changing the desktop-file-utils and
> >    shared-mime-info triggers *in stable* to -noawait should make the
> >    problem go away.
> > 
> >  * I realise it is unfeasible to implement in Debian by Saturday, but
> >    it would help us understand the root cause of the problem.
> >    - Tests to confirm/disprove this would be very welcome.
> 
> I think I can't confirm this theory. What I did:
> 
> A) Round 1: reproduce the problem:
> 
> 1) enter a jessie cowbuilder chroot
> 2) rm /etc/apt/apt.conf.d/15pbuilder # which turns off installing recommends
> 3) apt-get install task-gnome-desktop
> 4) sed -i -e 's/jessie/stretch/g' /etc/apt/sources.list
> 5) apt-get update
> 6) apt-get upgrade
> 7) apt-get dist-upgrade
> 
> Result:
[…]

> B) Round 2: play with triggers:
> 
> Same as above, except that after 3) I did
> 
> 3a) sed -i -e 's/interest /interest-noawait /' /var/lib/dpkg/info/{desktop-file-utils,shared-mime-info}.triggers
> 
> and after 6) I again ran
> 
> 6a) sed -i -e 's/interest /interest-noawait /' /var/lib/dpkg/info/{desktop-file-utils,shared-mime-info}.triggers

The important file to modify in addition is actually
/var/lib/dpkg/triggers/File, "/noawait" would need to be appended to
the relevant lines. The individual .triggers files for this scenario are
pretty much just parsed on unpack and removals.

Thanks,
Guillem