Bug#715557: apt: upgrade system is broken when a package is removed from Debian

[David Kalnischkies <kalnischkies+debian@gmail.com>]

On Wed, Jul 10, 2013 at 2:32 PM, Vincent Lefevre <vincent@vinc17.net> wrote:
> # apt-get install clang
> The following packages have unmet dependencies:
>  clang : Depends: clang-3.2 (>= 3.2-1~) but it is not going to be installed
> E: Unable to correct problems, you have held broken packages.
>
> This is due to:

clang is no longer in unstable (the package – and its not the
 reason, but I wouldn't expect it to work based on that)


> Even though this appears to be a downgrade of libclang-common-dev,
> the installation should obviously be forced in such a case.

Downgrades are not supported in Debian, so its even more obvious that
APT shouldn't actively trying to destroy your system without heavy force
applied as old packages might be unable to read their new conf file formats,
irreversible maintainer-script actions (which the maintainer has to code
 of course - at best bug-free as it is already done for the more common
 "upgrade" scenario), …

Given that you hit this problem only if a maintainer hasn't cared too much
for the upgradeability of the package, I wouldn't have too much hope that
the maintainer has cared all that much for downgrades …


Beside: Detecting this would be pretty hard and full of cornercases
(especially as yours is already one as it crosses source-package boundaries):
It wouldn't be that great if a package is removed from testing and the
package gets therefore downgraded to a version from stable for example…

So, as this is (at least not without a debian-policy enforced MUST for
 the support of downgrades in packages) never going to happen:
Obviously Closing.


Best regards

David Kalnischkies