Re: Contribute or create a channel?

[Josselin Poiret]

Hi Attila,

Attila Lendvai <attila@lendvai.name> writes:

>> > channels are a step towards this, but they are not enough in their
>> > current form to successfully accommodate for such a setup. an obvious
>> > thing that is missing is a way to formally express inter-channel
>> > dependencies, including some form of versioning.
>> 
>> 
>> Do we not have this? The manual documents a mechanism for channel
>> dependencies in "(guix) Declaring Channel Dependencies".
>> 
>> I haven't used it, but it looks like the dependencies are declared as
>> channels, which can have the usual branch/commit specifications to tie
>> them to specific versions.
>
> good point, thanks!
>
> i looked briefly at the code just now. it's not trivial, and it seems to 
> treat the guix channel specially (because i don't need to specify it as a 
> dependency in my channel's .guix-channel file), and i'm not sure how it 
> behaves when e.g. two channels depend on the same channel, but pick two 
> different commits... or all the other convoluted situations.

The situation you describe where two channels pick different commits for
a channel dependency *cannot* be made to work, at least using Guile.  I
think what would currently happen is that either:

1) Guix refuses to build (unlikely);
2) Guix just chooses one commit that it then uses to build all dependent
channels, contrary to the requirements;
3) Guix does build each channel with the proper dependencies, but the
final Guix will have profile collisions.

Best,
-- 
Josselin Poiret

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