haskell.nix is an experimental new builder for Haskell packages.

It works by automatically translating your Cabal or Stack project and its dependencies into Nix code. It provides IFD (imports from derviation) functions that can minimize the amount of nix code you need to add.

For the documentation, see https://input-output-hk.github.io/haskell.nix/.

For cabal.project project add a default.nix:

{ pkgs ? import <nixpkgs> (import (builtins.fetchTarball https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz))
, haskellCompiler ? "ghc865"
}:
  pkgs.haskell-nix.cabalProject {
    src = pkgs.haskell-nix.haskellLib.cleanGit { src = ./.; };
    ghc = pkgs.buildPackages.pkgs.haskell-nix.compiler.${haskellCompiler};
  }

For a stack.yaml project add a default.nix:

{ pkgs ? import <nixpkgs> (import (builtins.fetchTarball https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz))
}:
  pkgs.haskell-nix.stackProject {
    src = pkgs.haskell-nix.haskellLib.cleanGit { src = ./.; };
  }

To build the library component of a package in the project run:

nix build -f . your-package-name.components.library

To build an executable:

nix build -f . your-package-name.components.exes.your-exe-name

To open a shell for use with `cabal` run:

nix-shell -A shellFor
cabal new-build your-package-name
cabal new-repl your-package-name:library:your-package-name

CI pushes to cachix so you can benefit from the cache if you pin a combination of haskell.nix and nixpkgs built by CI.

You’ll need to configure the nix-tools cachix as a substituter for nix and add the public key found at the url to trusted-public-keys.

The haskell.nix repository contains the runtime system for building Haskell packages in Nix. It depends on other repos, which are:

• nix-tools — provides the programs for generating Nix expressions from Haskell projects.
• hackage.nix — the latest contents of the Hackage databases, converted to Nix expressions.
• stackage.nix — all of the Stackage snapshots, converted to Nix expressions.

Join the #haskell.nix channel on irc.freenode.net to get help or discuss the development of haskell.nix and nix-tools.