[pacman-dev] [PATCH] Add more information in conflicts question

[Rémy Oudompheng]

On Sun 17 April 2011 at 23:40 +0800, Sebastian Nowicki wrote:
> On Sun, Apr 17, 2011 at 5:50 PM, Rémy Oudompheng
> <remyoudompheng at gmail.com> wrote:
> >
> > I am totally against this. Really really totally.
> >
> > I personally think a formatting function for package information has
> > strictly nothing to do in sync.c, and maybe not even in libalpm.
> > Second, it would introduce additional parsing effort from front-ends to
> > split against the passed string if they want to display information in a
> > different way.
> 
> Agreed, but the alternatives require changes to the API (char * -> pmpkg_t).

I think we disagree in what we call an API change. All the suggested
patches are API changes in the sens that they change the behaviour of a
function. Even if its type signature does not change, the behaviour
changes in the sense that the nature of what is returned changes.

As you already noticed, going from a simple package name to a complex
string changes a lot of things when considering what a user (developer)
may want to do with it.

The only advantage is keeping binary compatibility for several
applications, e.g. pacman, but that is a coincidence.

> > And what output do you expect if a conflict arises when running
> > pacman -U ?? What do you think is the repository from a package loaded
> > from a file.
> 
> Just the package name and version. Having a "file/" prefix would be
> meaningless, and if you're installing from a single file, you're
> likely to know what you're installing anyway.

Is there is a reason you don't know what you are installing in other
cases? Possible from the point of view of the user, not very improbable
from the point of view of the program using libalpm.

> > I don't even understand why we would want to display any sort of version
> > information. I don't see how it would help me answer yes or no to that
> > conflict question either.
> >
> > That is in my mind the job of the front-end: if you really
> > want information, it should display the list of selected packages
> > (repository/pkgname-pkgver) that comes between the parsing of the
> > command-line and the beginning of the transaction.
> >
> > For example:
> >
> > cb_trans_conv (from pacman) should be patched to display :
> >  :: target qemu-kvm conflicts with installed qemu. Remove qemu ?
> >
> > which is perfectly clear: qemu is installed and pacman wants you to
> > remove it, "local/qemu" brings no additional information, and the version
> > number is usually meaningless. The callback returns precisely one local
> > package and one target package, it can be reflected in the user output.
> 
> If the version of the local package is newer than the one being
> installed, it would be good to inform the user (as would have been
> likely with the libdrm-git package). The "local/" prefix can easily be
> omitted.

I don't see why the version information is particularly more relevant
than other things. Personnally I'm interested in knowing whether my local
package comes from an official repository, if so, whether it's in
testing... Things that still not solved using such a partial approach.

Does knowing the version really helps you in answering yes or no ???

> > If you need to display the version number, then I don't feel like
> > messing with libalpm's internals is the right answer. I would probably
> > prefer have process_targname() patched (in pacman/sync.c), so that
> > after running alpm_find_dbs_satisfier(), it prints something.
> 
> I think that changing the API of the callback to use pmpkg_t, (or even
> pmconflict_t if that's exposed) rather than a string, is the right
> thing to do. The front-end shouldn't have to find the package again to
> get its metadata (what if there are multiple packages with the same
> name?).

The front-end doesn't have to do anything magic to find what packages are
in the transaction. Simple calls to alpm_find_satisfier() and
alpm_trans_get_add() suffice to find the culprit package (even if
of course having the whole pmpkg_t structure would be better).

> > However, I think modifying the callback to return pmpkg_t is not a bad
> > idea, but then the formatting function should go in pacman. I just want
> > to understand the first reason why we are doing this. The bug report is
> > totally inconsistent (the title is inconsistent with the described
> > problem and so on), and it seems we are trying to solve some imaginary
> > problem.
> >
> > The best thing we can probably do is make libalpm functions return more
> > information about their internal processing. Modifying formatting will
> > not help that. And if people want to know why some package suddenly
> > appears in the target list, I fear there is no solution.
> 
> In which case the API needs to change. I don't think cosmetic changes
> are worth doing so, but that's a decision for the devs.

Again, the patch indeed *is* an API change, and as yourself say,
isn't worth the trouble for what should be a cosmetic patch for pacman.

-- 
Rémy.