haskell-flake - Ergonomic Nix module for Haskell development

There are several ways to manage Haskell packages using Nix with varying degrees of integration. haskell-flake makes Haskell development, packaging and deployment with Nix a lot simpler than other existing approaches. It works with plain Nix (no flakes), Nix flakes, or as a flake-parts module—choose whichever fits your project.

To see more background information, guides and best practices, visit https://haskell.nixos.asia

Caveat: haskell-flake only supports the Haskell package manager Cabal, so your project must have a top-level .cabal file (single package project) or a cabal.project file (multi-package project).

Getting started

The guide below uses flake-parts; for other approaches see standalone usage.

The minimal changes to your flake.nix to introduce haskell-flake with flake-parts will look similar to:

# file: flake.nix
{
  inputs = {
    ...
    flake-parts.url = "github:hercules-ci/flake-parts";
    haskell-flake.url = "github:srid/haskell-flake";
  };

  outputs = inputs:
    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
      systems = [ "x86_64-linux", ... ];
      imports = [
        ...
        inputs.haskell-flake.flakeModule
      ];
      perSystem = { self', system, lib, config, pkgs, ... }: {
        haskellProjects.default = {
          # basePackages = pkgs.haskellPackages;

          # Packages to add on top of `basePackages`, e.g. from Hackage
          packages = {
            aeson.source = "1.5.0.0"; # Hackage version
          };

          # my-haskell-package development shell configuration
          devShell = {
            hlsCheck.enable = false;
          };

          # What should haskell-flake add to flake outputs?
          autoWire = [ "packages" "apps" "checks" ]; # Wire all but the devShell
        };

        devShells.default = pkgs.mkShell {
          name = "my-haskell-package custom development shell";
          inputsFrom = [
            ...
            config.haskellProjects.default.outputs.devShell
          ];
          nativeBuildInputs = with pkgs; [
            # other development tools.
          ];
        };
      };
    };
}

haskell-flake scans your folder automatically for a .cabal or cabal.project file. In this example an imaginary my-haskell-package.cabal project is used.

To see in more detail how to use haskell-flake in a realistic Haskell project with several other development tools, take a look at the corresponding Haskell single-package project Nix template and this Haskell multi-package project Nix example.

Documentation

https://haskell.nixos.asia

Discussion

Please post questions & ideas in Github Discussions.