[Nix-dev] Help with ghc errors after nix-channel --update

[Carlo Nucera]

Hi all. I managed to create a nice setup for haskell
development. However, I did:

$ sudo nix-channel --update
$ sudo nixos-channel rebuild

After updating, my haskell installation is broken, ghc-pkg check is
full of errors, and the packages I installed no longer load in ghci.
I could rollback but there are new packages I need which are in the
recent nixos-unstable commits.

So, here is the setup I use:

$ sudo nix-channel --list
nixos http://nixos.org/channels/nixos-unstable

$ nix-channel --list
# no output

My global nixos config:
https://github.com/meditans/settings/blob/master/nixos/configuration.nix

My ~/.nix-pkgs/config.nix:
https://github.com/meditans/settings/blob/master/nix-local/config.nix

$ ghc-pkg list
output: http://lpaste.net/115809

$ ghc-pkg check
output: http://lpaste.net/115810

$ nix-env -q

cabal-install-1.20.0.3
cabal2nix-1.72
ghc-7.8.3-wrapper
haskell-abcnotation-ghc7.8.3-1.8-shared
haskell-applicative-numbers-ghc7.8.3-0.1.3-shared
haskell-data-interval-ghc7.8.3-1.1.1-shared
haskell-extended-reals-ghc7.8.3-0.1.0.0-shared
haskell-lattices-ghc7.8.3-1.2.1.1-shared
haskell-lilypond-ghc7.8.3-1.8-shared
haskell-music-dynamics-literal-ghc7.8.3-1.8-shared
haskell-music-pitch-literal-ghc7.8.3-1.8-shared
haskell-musicxml2-ghc7.8.3-1.8-shared
haskell-positive-ghc7.8.3-0.4-shared
haskell-prettify-ghc7.8.3-1.0-shared
haskell-reverse-apply-ghc7.8.3-2.0.1-shared
haskell-ty-ghc7.8.3-0.1.6-shared
haskell-type-unary-ghc7.8.3-0.2.16-shared

$ ghci
GHCi, version 7.8.3: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> import Music.Abc

<no location info>:
    Could not find module ‘Music.Abc’
    It is not a module in the current program, or in any known package.

It's in this way for all the packages I'm trying to install.
Any suggestion on what to do?

Carlo Nucera