rpm 4.12 and weak dependencies

[Panu Matilainen]

On 10/09/2014 10:04 PM, Kevin Fenzi wrote:
> On Thu, 9 Oct 2014 18:05:03 +0200
> Michael Schroeder <mls at suse.de> wrote:
>
>> On Thu, Oct 09, 2014 at 11:03:20AM -0400, Miloslav Trma?? wrote:
>>> [...]
>>> That documentation belongs upstream (and should _not_ be just
>>> repeated within our packaging guidelines IMHO).
>>
>>  From an rpm upstream point of view, we don't know much about what
>> those dependencies do. We simply relay the information from
>> the packager to the dependency solver tool.
>>
>>> Rather, there are Fedora-specific questions to figure out.
>>>
>>> * That page says that Suggests/Enhances: will prompt the user.  Do
>>> any of the Fedora tools actually do that?  Do the _relevant_ tools
>>> do that?  If not, we shouldn???t be using these tags I guess.
>>
>> DNF does not do anything with Suggests/Enhances. Libsolv uses them
>> to tiebreak decisions if multiple packages provide something.
>
> ok. That helps resolve (ha) most of my concerns.
>
> I also took a closer look at the packages using these currently:
>
> bcfg2 - false positive, it's actually defined out in fedora.
>
> ceph - This seems like a bug to me. It has a "Suggests: logrotate" but
> it's installing logrotate files, so I would think it should just be
> Requiring it since it needs something to make those directories?
>
> dreamchess - This behaves completely the same in yum or dnf. The
> Suggests: gnuchess doesn't do anything at all (since as you say it only
> would use it as a tiebreaker).
>
> So, as long as both dnf and yum essentially ignore these for now we
> should be ok. I'm really not sure why someone would add them actually
> since they don't do anything, but ok.

Note that Michael is talking about Suggests and Enhances specifically: 
these "very weak" dependencies are ignored by dnf. Recommends and 
Supplements do affect dnf operation (although its probably libsolv 
pulling the strings here), so yum, dnf and anything using them for 
depsolving behave differently if these are present.

	- Panu -