Teach cabal2nix how to generate shell.nix too about cabal2nix HOT 6 CLOSED

Implemented --shell flag.

from cabal2nix.

Nice! Did you consider putting this on the NixOS wiki?

from cabal2nix.

@ocharles, it would be really nice if cabal2nix could generate that kind of setup automatically! In fact, I need almost exactly the same thing for configuring Haskell hydra builds (see https://github.com/peti/ci/blob/master/largeword.nix for an example). Another interested party might be the buildLocalCabalWithArgs crowd, who patch cabal2nix output to achieve a similar result.

I think I can teach cabal2nix how to generate those files. The biggest challenge is, basically, to re-factor the program internally so that there is a cleaner separation between Nix-specific know-how and the part that generates the actual output from that. It's not rocket science, but still it needs to be done. I'll take a look into that subject.

from cabal2nix.

Maybe you could instead use a setup like the following one?

{ haskellPackages ? (import <nixpkgs> {}).haskellPackages }:

let
  haskellPackagesCustom = haskellPackages.override {
    extension = self: super: {
      # Here packages can be overriden
      # Ex: Use a modified comonad package (which uses same setup)
      # comonad = import /data/libs/comonad { inherit haskellPackages; };
    };
  };

haskellPackagesCustom.callPackage ./. {}

This setup has the advantage that the shell.nix file doesn't depend on the project at all (except for the overrides, which cabal2nix couldn't generate anyway) so it could just be copied from a template.

from cabal2nix.

That could work, but I need to make sure cabal-install is added to the build inputs too - but that should be doable with out giving the project a name.

from cabal2nix.

I'm using the following variation on the code above, which lets me specify a non-default pkgs, or haskellPackages, and I can paste it in from a template. You can ignore the hsPkg bit, which I use for version pinning.

{ pkgs ? import <nixpkgs> {}, haskellPackages ? pkgs.haskellPackages }:

let 
  hs = haskellPackages.override {
        extension = self: super: rec {
          hsPkg = pkg: version: self.callPackage "/home/bergey/code/nixHaskellVersioned/${pkg}/${version}.nix" {};
          thisPackage = self.callPackage ./. {};
      };
    };
  in
      pkgs.lib.overrideDerivation hs.thisPackage (attrs: {
       buildInputs = [hs.cabalInstall ] ++ attrs.buildInputs;
 })

from cabal2nix.