Re: Conflicts in the meta spec

On 17.04.13 20:43, Michael G. Schwern wrote:
> On 4/15/13 7:06 PM, Jens Rehsack wrote:
>> On 15.04.13 18:56, Michael G. Schwern wrote:
>>> TL;DR version...
>>> IMO we only need to clarify what "conflicts" means and what actions CPAN
>>> tools should take.
>>>
>>> We talked in the Consensus Dome about the need for and meaning of the
>>> "conflicts" relationship in the CPAN::Meta::Spec.
>>> https://metacpan.org/module/CPAN::Meta::Spec#Prereq-Spec
>>>
>>> IIRC the conclusion was...
>>> * We need it.
>>> * It's not clear what it means. (I don't recall what the confusion was)
>>
>> The difference between "A conflicts with B op VER" and "A breaks B op
>> VER" and "A superflous B".
>
> IIRC those meant...
>
> "A conflict B" is A and B cannot be on the machine at the same time.
> For example, they're both http servers and need the same port.  I can't
> think of an example where CPAN has needed that for modules.

Or - maybe - an ancient distribution (META spec is per dist)
is mis-using a module name, and my shiny-new-dist uses the same.
This might be a candidate for superfluous, but doesn't need to...

> "A breaks B" is if A is installed B will break.  This is what we need on
> CPAN for things like Test::Builder breaks Test::Class < 0.39.

Yes.

> "A superfluous B" is if A is installed B is no longer necessary.
> Usually called "obsoletes".  This is mostly useful if you rename a
> package, though I'd rather that was made more explicit in the meta data.
>   Most of the use cases I can think of are better handled by the
> installed modules database and CPAN distribution meta data.

Looking to XML-LibXML, that extra knowlegde of consequences of
splitting and remerging dists could had helped to avoid a lot
of confusion around XML::LibXML::XPathContext.

>>> * Let's see what Debian does.
>>
>> Or MacPorts, HomeBrew or pkgsrc :P
>
> Whatever packaging system I may actually use, I go to Debian first
> because they extensively document this sort of thing, both the meanings
> and the rationales.

I don't know how Debian docs are - I see only the results ;)

> Let's have a look at what the others do...

I suggest we're asking some of the developers there ...

> pkgsrc has CONFLICTS=Some-Name-[0-9]* essentially a regex.
> http://www.netbsd.org/docs/pkgsrc/fixes.html#conflicts
> All they say is the "package may conflict with other packages a user
> might already have installed on his system"

We also allow "patterns" like "scrnsaverproto<1.2.0".
That's why I recommended to look what "the others do" - not
what is somewhere described ;)

...

Cheers,
Jens