hello Cabal2nix

Disclaimer There are many ways to build a Haskell project on Nix, this approach use cabal2nix that just work but might not be the best way to do it.

Contents

• default.nix : The Nix's expression

{ nixpkgs ? import <nixpkgs> {} }:
with nixpkgs;

let
  drv = haskellPackages.callCabal2nix "hello" ./. {};

  hsTools = with haskellPackages; [
    cabal-install hpack
    hlint hdevtools
  ];

  dev = drv.env.overrideAttrs(attr: {
    buildInputs = attr.buildInputs
               ++ hsTools;
  });

in
  if pkgs.lib.inNixShell then dev else drv

• Main.hs : Program source code

main = print "Hello"

• package.yaml : Project description (hpack)

name: hello

dependencies:
  - base

executables:
  hello:
    main: Main.hs

To build and run

$ nix-build

$ result/bin/hello
"Hello"

To dev

The dev env for nix-shell included additional tools for development.

$ nix-shell

$ cabal new-run hello

$ hlint Main.hs
$ hdevtools Main.hs

Gotcha

cabal new-build generate .ghc.environment.xxxx which block nix-build, remove that file if there is build error when running nix-build.