stack2nix

stack2nix converts a Stack file into a Nix Haskell packages set. It creates LTS Stackage packages set, and applies appropriate overrides on top of it.

stack2nix \
  --lts-haskell "$LTS_HASKELL_REPO" \
  --all-cabal-hashes "$ALL_CABAL_HASHES_REPO" \
  .

stack2nix has three required arguments:

• --lts-haskell - path to fpco/lts-haskell
• --all-cabal-hashes - path to commercialhaskell/all-cabal-hashes checked out to hackage branch
• . - path to stack.yaml file or directory

Produced Nix derivation split on following files:

• packages.nix - Base Stackage packages set
• configuration-packages.nix - Compiler configuration
• default.nix - Final Haskell packages set with all overrides applied

A particular package from result Haskell packages set can be built with:

nix-build -A <package-name>

Override result derivation

Complex projects may require some extra customization. Snippet override.nix below is a minimal example of Haskell packages override.

with import <nixpkgs> {};
with pkgs.haskell.lib;
let haskellPackages = import ./. {};
in haskellPackages.override {
  overrides = self: super: {
    stack2nix = disableSharedExecutables super.stack2nix;
  };
}

nix-build -A stack2nix override.nix

For more complex overrides and detailed information on how to work with Haskell packages in Nix, see Nixpkgs manual User’s Guide to the Haskell Infrastructure

Examples

For other examples of stack2nix usage, see 4e6/stack2nix-examples repository. It verifies stack2nix by running it on different public projects.