From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <rekado@elephly.net>
Subject: Re: [PATCH 2/2] gnu: Remove ghc-parsec, ghc-stm, ghc-text, ghc-xhtml.
Date: Sat, 06 Jul 2019 10:21:57 +0200
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To: Robert Vollmert <rob@vllmrt.net>
Cc: guix-devel@gnu.org, 36493@debbugs.gnu.org


Hi Robert,

> Could we do something in guix like what nixpkgs does, where the dependenc=
ies
> are encoded, but then =E2=80=9Cnulled=E2=80=9D depending on the compiler =
version?
>
> https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-mod=
ules/configuration-ghc-8.4.x.nix#L10

Yes, we could do this in the haskell-build-system (automatically
removing inputs before the build is set up).  My first reaction was
=E2=80=9Cthis is inelegant=E2=80=9D, but it does have some advantages: we c=
ould rebuild
packages with other versions of GHC more easily and it would just work
without having to adjust the inputs manually.

I think this would be done in guix/build-system/haskell.scm, the
=E2=80=9Chaskell-build=E2=80=9D procedure.  There we pass all inputs unchan=
ged through
to build-expression->derivation.  I guess we could filter inputs right
there.

--
Ricardo