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

[Matthias Beyer]

Hi Peter,

thanks, thanks for your suggestion, now I got it working.

Unfortunately, I cannot `cabal build` because of one recursive
dependency is missing:

    $ cabal build
    Building ratehs-0.1...
    Preprocessing executable 'ratehs' for ratehs-0.1...
    <command line>: cannot satisfy -package-id
    snap-0.14.0.2-ef658c66823be8387d049aa89445f690: 
    snap-0.14.0.2-ef658c66823be8387d049aa89445f690 is unusable due
    to missing or recursive dependencies:
    clientsession-0.9.1.1-f379c9ed2e350715ba6cdc20d73894b3
    (use -v for more information)

Do you have an idea how I can fix this?

I'll send you my default.nix / shell.nix and cabal file, if you need
them, but basically they say (pseudo-code):

    env = haskellngPackages.ghcWithPackages ...
        pkgs.stdenv
        cabal-install
        hlint

        snap
        snap-core
        snap-server
        snap-loader-static

        snaplet-persistent
        persistent
        persistent-postgresql
        persistent-sqlite

        heist

and

    Build-depends:
        heist
        persistent
        persistent-postgresql
        persistent-sqlite
        snap
        snap-core
        snap-server
        snap-loader-static

(and everything else which is generated by `snap init`, of course.

On 22-05-2015 21:44:30, Peter Simons wrote:
> Hi Peter,
> 
>  > 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.)
> 
> I use the following "shell.nix" to switch between compiler versions:
> 
>     { compiler ? "ghc7101" }:
> 
>     with (import <nixpkgs> {}).pkgs;
>     let
>       ghc = haskell.packages.${compiler}.ghcWithPackages
>               (pkgs: with pkgs; [ aeson lens monad-par ]);
>     in
>     stdenv.mkDerivation {
>       name = "my-haskell-env-0";
>       buildInputs = [ ghc ];
>       shellHook = "eval $(grep export ${ghc}/bin/ghc)";
>     }
> 
> Now run "nix-shell --argstr compiler ghc784" to select a compiler other
> than the default.
> 
> I hope this helps,
> Peter
> 
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-- 
Mit freundlichen Grüßen,
Kind regards,
Matthias Beyer

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