Re: propagating inputs in ghc-* packages

[Federico Beffa <beffa@ieee.org>]

>> Ricardo Wurmus <rekado@elephly.net> writes:
>>
>>> Hi Guix,
>>>
>>> I’m in the middle of upgrading our Haskell packages.  (Actually, I’m
>>> just yak shaving.  I need “pandoc-citeproc” for “r-knitr”…)
>>>
>>> I noticed that upgrading Haskell packages is a pain in the neck because
>>> of propagated inputs.  It seems that not all packages have fully
>>> declared dependencies and just work accidentally because of propagated
>>> inputs of a related package.  This also makes upgrades more difficult
>>> because I can get substitutes from Hydra that depend on older versions
>>> of some Haskell packages.
>>>
>>> It looks like Haskell binaries actually embed references to other
>>> Haskell packages, so I’m not sure we actually need to propagate anything
>>> at all.  Could someone please confirm this?
>>
>> From what I recall, binary executables include references to packages,
>> but libraries do not.  So, at least at the time I wrote the first
>> version of the haskell-build-system, propagated inputs seemed to be
>> necessary for packages providing libraries, but not for ones providing
>> applications.
>
> Thanks for this comment.  With Eric Bavier’s patch this seems no longer
> necessary.  I’ve already rebuilt a lot of Haskell packages without any
> propagation (and some added inputs), and I’ve got working libraries and
> executables.  I’m still rebuilding remaining Haskell packages but I’m
> now convinced that propagation is no longer needed with the current
> version of the build system.
>
> I’m preparing a patch to remove propagation from all Haskell packages.
> Now the question is only whether to do this all in one patch or in one
> patch per package… :)

That sounds great! Just to be sure: you are saying that if you install
any library (call it A) and the GHC compiler into your profile then you
are able to compile your program (making use of library A) without
also having to manually install any input of library A?

Regards,
Fede