Bug#766260: perl: upgrade failure in jenkins: dependency problems prevent configuration of perl

[Niko Tyni]

Package: perl
Version: 5.20.1-1
Severity: serious

I'm not quite sure yet if this is a real problem or a one-off glitch,
but it deserves full investigation and I don't seem to have the time
for that right now. Help would be appreciated.

The jenkins wheezy->jessie upgrade test at
 https://jenkins.debian.net/job/chroot-installation_wheezy_install_haskell_upgrade_to_jessie/490/
failed when configuring the upgraded perl package because "perl-modules
is not configured yet."

This is weird. While there's an intentional circular dependency between
perl and perl-modules, it's been there for more than ten years and
countless systems have been upgraded between perl versions without
triggering this AFAIK. I don't think anything has changed in the
dependencies in this area.

Policy 7.2 says that "If one of the packages in the loop has no `postinst'
script, then the cycle will be broken at that package; this ensures
that all `postinst' scripts are run with their dependencies properly
configured if this is possible."

The perl-modules package doesn't have a postinst script but perl does.
So I'd expect perl-modules to be configured first, before perl. That
also seems to be what happens with a simple 'apt-get dist-upgrade'
of a smaller chroot.

Perhaps the '-f' (--fix-broken) part in the 'apt-get -yf dist-upgrade'
below affects this?

xzipped full log attached, snippets:

  [in a just-prepared wheezy chroot]
  + apt-get -y install 'haskell-platform.*' 'libghc-.*'
  [...]
  [switch to jessie]
  + apt-get -y upgrade
  [...]
  [no change to perl-base/perl/perl-modules yet]
  + apt-get -yf dist-upgrade
  [...]
  Preparing to unpack .../perl_5.20.1-1_amd64.deb ...
  Unpacking perl (5.20.1-1) over (5.14.2-21+deb7u2) ...
  [...]
  Preparing to unpack .../perl-base_5.20.1-1_amd64.deb ...
  Unpacking perl-base (5.20.1-1) over (5.14.2-21+deb7u2) ...
  Processing triggers for man-db (2.7.0.2-1) ...
  Setting up perl-base (5.20.1-1) ...
  [...]
  Preparing to unpack .../perl-modules_5.20.1-1_all.deb ...
  Unpacking perl-modules (5.20.1-1) over (5.14.2-21+deb7u2) ...
  [...]
  dpkg: dependency problems prevent configuration of perl:
   perl depends on perl-modules (>= 5.20.1-1); however:
    Package perl-modules is not configured yet.
  
  dpkg: error processing package perl (--configure):
   dependency problems - leaving unconfigured

-- 
Niko Tyni   ntyni at debian.org
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