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.

Regards,
Fede