devx/flake.nix

{
    description = "Minimal devshell flake for haskell";

    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 }: 
    let overlays = {
         crypto = final: prev: {
          libsodium-vrf = final.callPackage ({ stdenv, lib, fetchFromGitHub, autoreconfHook }:
            stdenv.mkDerivation rec {
                name = "libsodium-1.0.18";

                src = fetchFromGitHub {
                    owner = "input-output-hk";
                    repo = "libsodium";
                    rev = "11bb20dba02b013bf1d83e3c16c51eab2ff07efc";
                    sha256 = "1h9fcwra610vmh0inkdkqs3bfs83xl5dk146dqx440wwh9pn4n4w";
                };

                nativeBuildInputs = [ autoreconfHook ];

                configureFlags = [ "--enable-static" ];

                outputs = [ "out" "dev" ];
                separateDebugInfo = stdenv.isLinux && stdenv.hostPlatform.libc != "musl";

                enableParallelBuilding = true;

                doCheck = true;

                meta = with lib; {
                    description = "A modern and easy-to-use crypto library - VRF fork";
                    homepage = "http://doc.libsodium.org/";
                    license = licenses.isc;
                    maintainers = [ "tdammers" "nclarke" ];
                    platforms = platforms.all;
                };
            }) {};
        };
         # the haskell inline-r package depends on internals of the R
         # project that have been hidden in R 4.2+. See
         # https://github.com/tweag/HaskellR/issues/374
         oldR = (final: prev: {
           R_4_1_3 = final.R.overrideDerivation (old: rec {
             version = "4.1.3";
             patches = []; # upstream patches will most likely break this build, as they are specific to a different version.
             src = final.fetchurl {
               url = "https://cran.r-project.org/src/base/R-${final.lib.versions.major version}/${old.pname}-${version}.tar.gz";
               sha256 = "sha256-Ff9bMzxhCUBgsqUunB2OxVzELdAp45yiKr2qkJUm/tY="; };
             });
         });
       };
       supportedSystems = [
            "x86_64-linux"
            "x86_64-darwin"
            "aarch64-linux"
            "aarch64-darwin"
       ];       
    in flake-utils.lib.eachSystem supportedSystems (system:
         let 
           pkgs = import nixpkgs {
             overlays = [haskellNix.overlay] ++ __attrValues overlays;
             inherit system;
             inherit (haskellNix) config;
           };
         in {
           # These are for checking IOG projects build in an environment
           # without haskell packages built by haskell.nix.
           #
           # Usage:
           #
           # nix develop github:input-output-hk/devx#ghc924 --no-write-lock-file -c cabal build
           #
           devShells = __mapAttrs (compiler-nix-name: compiler:
             pkgs.mkShell {
               buildInputs = [
                 compiler
                 pkgs.haskell-nix.cabal-install.${compiler-nix-name}
                 pkgs.pkgconfig
                 # for libstdc++; ghc not being able to find this properly is bad,
                 # it _should_ probably call out to a g++ or clang++ but doesn't.
                 pkgs.stdenv.cc.cc.lib
               ] ++ map pkgs.lib.getDev (with pkgs; [ libsodium-vrf secp256k1 R_4_1_3 zlib openssl ] ++ pkgs.lib.optional pkgs.stdenv.hostPlatform.isLinux systemd);
             }
           ) (builtins.removeAttrs pkgs.haskell-nix.compiler
               # Exclude old versions of GHC to speed up `nix flake check`
               [ "ghc844"
                 "ghc861" "ghc862" "ghc863" "ghc864"
                 "ghc881" "ghc882" "ghc883"
                 "ghc8101" "ghc8102" "ghc8103" "ghc8104" "ghc8105" "ghc8106" "ghc810420210212"
                 "ghc901"
                 "ghc921" "ghc922" "ghc923"]);
       });
}