Bug#808430: perl-modules-5.22: after the upgrade to perl 5.22, the Module::Build module is no longer present

[gregor herrmann]

On Sun, 20 Dec 2015 19:13:39 +0100, Vincent Lefevre wrote:

> On 2015-12-20 19:13:05 +0200, Niko Tyni wrote:
> > No, the 5.20 perl-modules packages (including the one in jessie) actually
> > did Recommend libmodule-build-perl, precisely to pull it in so that
> > people wouldn't lose it on upgrades. If aptitude automatically removes
> > it when the recommendation is gone, that's not working well together
> > with our intentions.
> Unfortunately, aptitude doesn't know the intention when a
> recommendation is dropped: in general, it means that the package
> became useless, but this is not the case here, where some feature
> is no longer there.

I was curious if I can reproduce this issue [0]:

- jessie chroot (from cowbuilder)
- rm /etc/apt/apt.conf.d/15pbuilder
  (APT::Install-Recommends "false";)
- aptitude install libmodule-build-perl+M
- make sure libmodule-build-perl is really marked auto
- sed -i -e 's/jessie/stretch/g' /etc/apt/sources.list
- aptitude update
- aptitude dist-upgrade
- allow aptitude to remove perl-modules
- let the upgrade run

Result:
libmodule-build-perl is still installed at this point. Good.
Opening aptitudes TUI then suggests to remove a bunch of perl
packages, among them libmodule-build-perl. Bad.

Without aptitude:
- jessie chroot (from cowbuilder)
- rm /etc/apt/apt.conf.d/15pbuilder
  (APT::Install-Recommends "false";)
- apt-get install libmodule-build-perl
- apt-mark auto libmodule-build-perl
- sed -i -e 's/jessie/stretch/g' /etc/apt/sources.list
- apt-get update
- apt-get dist-uprade

Result:
This throws away some automatically installed packages but not
libmodule-build-perl. Good.
apt-get autoremove then removes it. Bad.


The interesting point is that in both cases, libmodule-build-perl is
_not_ removed during the dist-upgrade. But it's "marked" as a removal
candidate and would need manual intervention to keep it.


For the future we might try to remember that having a Recommends in a
package which gets removed leaves the recommended package in an
"orphaned" state from the POV of apt{itude,-get}.
(In this case, IIRC, the decision to replace perl-modules by a
versioned package came only after the jessie release ...)


Cheers,
gregor
 

[0] On my real machines, libmodule-build-perl was already set to
manually installed before the upgrade.

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