[Nix-dev] Haskell-env (via nix-shell) - am I doing this right?

[Peter Jones]

Matthias Beyer <mail at beyermatthias.de> writes:
> I want to develop a haskell package, but I need haskell packages from
> haskellngPackages (what's the matter with haskellPackages vs.
> haskellngPackages?).
>
> So, I'm a bit insecure about my environment definition here, because I
> had to mix the non-ng-packages with the ng-packages to get the
> cabalInstall and everything (I'm rather new to Haskell, so maybe I
> completely messed up here.

I thought I'd chime in with how I'm developing Haskell package on NixOS.
I wouldn't say this is the correct way to do things, and I'm completely
open to feedback.

To start out, I'm using HaskellNG and a recent version of nixpkgs where
HaskellNG is the default.  Here are the components I use with some
examples:

  1) I write a default.nix that describes my dependencies:

        https://github.com/pjones/byline/blob/master/default.nix

  2) I write a shell.nix that pulls in default.nix using import:
  
        https://github.com/pjones/byline/blob/master/shell.nix

  3) The ghc argument in shell.nix allows me to specify different
     versions of GHC so I can test with multiple versions.  (I'd love
     some feedback on how to make this more flexible.)  This can be used
     from the command line like so:

        nix-shell --argstr ghc 7.10.1

        # or

        nix-shell --argstr ghc 7.8.4

  4) Once I'm inside nix-shell I use the buildPhase variable to build my
     package:

        eval $buildPhase

Again, any suggestions on how to improve this workflow are appreciated.

-- 
Peter Jones, Founder, Devalot.com
Defending the honor of good code