[Aptitude-devel] Bug#836708: aptitude: refuses to upgrade packages, 'g' says "Actions: no changes"

[Manuel A. Fernandez Montecelo]

2017-03-07 3:48 GMT+01:00 Vincent Lefevre <vincent at vinc17.net>:
> Control: reopen -1
>
> Hi,
>
> On 2017-03-06 22:57:18 +0100, Manuel A. Fernandez Montecelo wrote:
>> 2016-09-05 02:33 Vincent Lefevre:
>> > On 2016-09-05 01:50:04 +0200, Vincent Lefevre wrote:
>> > > In the UI, I've selected various packages for upgrade; I can see
>> > > no breakages. But the 'g' key doesn't have any effect, it just
>> > > says: "[1(1)/...] Actions: no changes" with no explanations.
>> >
>> > And 'e' (Examine) just says:
>> >
>> >  --\ Leave the following recommendations unresolved:
>> >    libmtp9 recommends libmtp-runtime
>> >
>> > libmtp9 recommends libmtp-runtime
>> > --\ The following actions will resolve this dependency:
>> >  -> Cancel the removal of libmtp-runtime
>> >  -> Downgrade libmtp-runtime [1.1.12-1 (now, testing, unstable) -> 1.1.8-1+b1 (
>> >  -> Leave the dependency "libmtp9 recommends libmtp-runtime" unresolved.
>> >
>> > which makes no sense since nothing related to libmtp is proposed.
>>
>> This was implemented after your complaint in #819636 (not upgrading
>> "lightly" if it means breaking a recommend relationship), which then
>> needed #822329 to not be so eager on fixing unfulfilled recommends.
>
> Except that libmtp-runtime was already installed, so that the
> dependency was satisfied! And I didn't request it to be removed.
> So, the above message is simply buggy.

libmtp9 recommends libmtp-runtime (no version), but libmtp-runtime
depends on libmtp9 (= ${binary:Version}), so they have to be upgraded
in lockstep (and now sure what part the binnmu version would play here
if libmpt-runtime was arch:all).  Maybe the broken recommendation is
related with them having to be in the same exact version.


> In any case, "Actions: no changes" is not a meaningful error message and
> isn't even documented anywhere (neither in the man page, nor in the manual).
> So, the fact that this message appears is a bug.

I don't agree that "actions: no changes" is a meaningful error
message, because that is not even an error message.

It's the proposed solution to solve an inconsistency in the (future)
state of a system.  In this context, "no changes" means to not
install, remove, upgrade etc. any package, and it's a perfectly valid
recommendation of the resolver to solve the inconsistency.

http://aptitude.alioth.debian.org/doc/en/ch02s03s03.html

"If a dependency problem arises that cannot be handled using the
immediate dependency resolver, aptitude can assist you in resolving
it. As soon as a problem occurs, a red bar will appear at the bottom
of the screen with a summary of aptitude's suggestion about how to fix
it. For instance, in the following screenshot, aptitude is indicating
that it can resolve the situation by keeping two packages at their
current versions."

"2 keeps" means to keep 2 packages instead of what the user requested
first, which was for example and upgrade.  "No changes" means to just
do nothing to solve the inconsistency with the Recommended package,
and it happens /now/ more frequently because of the bug fixed about
recommendations, mentioned above.


Cheers.
-- 
Manuel A. Fernandez Montecelo <manuel.montezelo at gmail.com>