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

[Vincent Lefevre]

On 2017-03-21 00:11:19 +0100, Manuel A. Fernandez Montecelo wrote:
> 2017-03-07 3:48 GMT+01:00 Vincent Lefevre <vincent at vinc17.net>:
> > 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.

The proposed action "Downgrade libmtp-runtime [1.1.12-1 (now, testing,
unstable) -> 1.1.8-1+b1" would have broken the dependency.

Why wasn't the following action proposed?

  Keep the ... packages at their current 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.

It is not clear that this is a decision from the resolver. I thought
it meant that the user requested no changes.

Something like the following would be clearer:

  The resolver decides: no changes.

Well, the resolver should be mentioned in the message.

Or perhaps better than "no changes":

  ...: keep all packages at their current version.

("no changes" is too vague, IMHO).

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)