Bug#752989: libio-callback-perl: FTBFS with Perl 5.20: alternative dependencies

[Jonas Smedegaard]

Quoting Niko Tyni (2014-06-28 14:57:01)
> On Sat, Jun 28, 2014 at 02:18:13PM +0200, Jonas Smedegaard wrote:
>> Quoting Niko Tyni (2014-06-28 13:44:57)
>>> On Sat, Jun 28, 2014 at 09:41:46AM +0200, Jonas Smedegaard wrote:
>
>>>> Relying on a (build-)dependency being resolved by a virtual package 
>>>> is not allowed by Policy, with the reasoning that it causes 
>>>> non-deterministic behaviour.
>>>
>>> Which policy clause is that?
>>
>> Oh well - I might be wrong and it is "just" an overly strong 
>> interpretation by ftpmasters that I have experienced in the past.
>> 
>> Or perhaps it is not an overly strong interpretation, but a real 
>> sensible one which has just not yet been codified in Policy.
>> 
>> Do you find the reasoning I gave non-sensical?
>
> I don't find it particularly relevant to this case.

I don't understand.  Do you not find it relevant for perl modules to 
declare to declare dependencies and build-dependencies 
deterministically, or do you find that this particular use of "|" does 
not affect determinism?


> I think it's about situations where multiple packages provide the same 
> virtual package, so dependency resolvers need to pick one at random if 
> none are installed and there are no hints provided.

As quoted above, I believe it is about deterministic build environment.

If package A depends on "X | Y" you might think that X will always be 
chosen when available.  But what if package B depends on "Y | X" and 
both A and B are installed - which packages are then pulled in?


> In the context of dual lived Perl modules, I think we've been relying 
> on virtual packages satisfying build dependencies for a long time and 
> there isn't any non-deterministic behaviour about them.

Could you provide some examples of what you mean by that?

I believe Perl modules are no different from other packages, and care 
must be taken to ensure deterministic (build-)dependencies.

Would be nice if it turns out I have been far too strict in my 
dependency handling for perl modules.


 - Jonas

-- 
 * Jonas Smedegaard - idealist & Internet-arkitekt
 * Tlf.: +45 40843136  Website: http://dr.jones.dk/

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