flake.nix

{
  description = "A very basic flake for stack2nix";
  inputs.haskellNix.url = "github:input-output-hk/haskell.nix";
  inputs.nixpkgs.follows = "haskellNix/nixpkgs-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  outputs = { self, nixpkgs, flake-utils, haskellNix }:
    flake-utils.lib.eachSystem [ "x86_64-linux" "x86_64-darwin" ] (system:
    let
      overlays = [ haskellNix.overlay
        (final: prev: {
          stack2cabal =
            final.haskell-nix.project' {
              src = ./.;
              compiler-nix-name = "ghc8107";
              projectFileName = "cabal.project";
              # This is used by `nix develop .` to open a shell for use with
              # `cabal`, `hlint` and `haskell-language-server`
              shell.tools = {
                # TODO: Fix: current workaround is to get it from shell.buildInputs
                # stack = {};
                cabal = {};
                haskell-language-server = {};
              };
              # Non-Haskell shell tools go here
              shell.buildInputs = with pkgs; [
                stack
                nixpkgs-fmt
              ];
            };
        })
      ];
      pkgs = import nixpkgs { inherit system overlays; inherit (haskellNix) config; };
      flake = pkgs.stack2cabal.flake {
        # This adds support for `nix build .#js-unknown-ghcjs:hello:exe:hello`
        # crossPlatforms = p: [p.ghcjs];
      };
    in flake // {
      # Built by `nix build .`
      defaultPackage = flake.packages."stack2cabal:exe:stack2cabal";
      # Ran by `nix run`
      defaultApp =  flake.packages."stack2cabal:exe:stack2cabal";
    });
  # --- Flake Local Nix Configuration ----------------------------
  nixConfig = {
    # This sets the flake to use the IOG nix cache.
    # Nix should ask for permission before using it,
    # but remove it here if you do not want it to.
    extra-substituters = ["https://cache.iog.io"];
    extra-trusted-public-keys = ["hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="];
    allow-import-from-derivation = "true";
  };

}