{
  description = "build dummy D package using dub build tool";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  outputs = {
    self,
    nixpkgs,
    flake-utils,
    ...
  }@inputs: let
    pname = "dummy";
    version = "0.1.0";
    shell = ./shell.nix;
    devEnv = ./nixDevEnv.sh; # ./.envrc;
    supportedSystems = ["x86_64-linux"]; # [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];
    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
    nixpkgsFor = forAllSystems (system: import nixpkgs {inherit system;});
    checkPhase = ''
      runHook preCheck
      #dub test --combined --skip-registry=all
      runHook postCheck
    '';
    localOverlay = (final: prev: {
      ldc = prev.callPackage ./nix-overlays/ldc {  };       # -> ok 1.39.0
      dmd = prev.callPackage ./nix-overlays/dmd {  };       # -> ok 2.109.0
      dub = prev.callPackage ./nix-overlays/dub {  };       # -> ? 1.36.0
      dtools = prev.callPackage ./nix-overlays/dtools {  }; # -> ok 2.103.1
      #gdc = prev.callPackage ./nix-overlays/gdc {  };      # empty
    });
    pkgsForSystem = system: import nixpkgs {
      overlays = [
        localOverlay
      ];
      inherit system;
    };
    installPhase = ''
      runHook preInstall
      mkdir -p $out/bin
      install -m755 ./bin/dummy $out/bin/dummy
      runHook postInstall
    '';
    postInstall = ''
      echo `ls -la $out/bin/dummy`
      $out/bin/dummy -v
    '';
  in {
    packages = forAllSystems (system: let
      pkgs-ovl = pkgsForSystem system;
      pkgs-nix = nixpkgsFor.${system};
    in
      with pkgs-ovl; {
        default = tilix;
        check-tilix = tilix;
        check-local-dir-build = stdenv.mkDerivation {
          inherit pname;
          inherit version;
          meta.mainProgram = "dummy";
          executable = true;
          src = self;
          inherit shell;
          inherit devEnv;
          buildInputs = [sqlite];
          nativeBuildInputs = [dub ldc gnumake]; # [ dub dmd ]; [ dub ldc ]; [ dub gdc ];
          buildPhase = ''
            runHook preBuild
            for DC_ in dmd ldmd2 ldc2 gdc gdmd; do
              echo "- check for D compiler $DC_"
              DC=$(type -P $DC_ || echo "")
              if [ ! "$DC" == "" ]; then break; fi
            done
            if [ "$DC" == "" ]; then exit "Error: could not find D compiler"; fi
            echo "$DC_ used as D compiler to build $pname"
            dub build --cache=local --compiler=$DC --build=$DC_ --combined --skip-registry=all
            runHook postBuild
          '';
          inherit checkPhase;
          inherit installPhase;
          inherit postInstall;
        };
      });
    devShells = forAllSystems (system: let
      pkgs-ovl = pkgsForSystem system;
      pkgs-nix = nixpkgsFor.${system};
      shellHook = ''
      '';
    in
      with pkgs-ovl; {
        dsh-overlay-dtools = mkShell {
          name = "overlay - ldc-1.39.0 - dub-1.36.0 - dtools-2.103.1";
          inherit shell;
          inherit devEnv;
          packages = [
            gnumake
            ldc
            dub
            dtools
          ];
          inherit shellHook;
        };
        dsh-overlay-ldc-dub = mkShell {
          name = "overlay - ldc-1.39.0 - dub-1.36.0";
          inherit shell;
          inherit devEnv;
          packages = [
            gnumake
            ldc
            dub
          ];
          inherit shellHook;
        };
        dsh-overlay-dmd-dub = mkShell {
          name = "overlay - dmd-2.109.0 - dub-1.36.0";
          inherit shell;
          inherit devEnv;
          packages = [
            gnumake
            dmd
            dub
          ];
          inherit shellHook;
        };
        dsh-overlay-dtest-tilix = mkShell {
          name = "overlay - ldc-1.39.0 - dub-1.36.0 - tilix - gtkd";
          inherit shell;
          inherit devEnv;
          packages = [
            gnumake
            ldc
            gtkd
            tilix
            dub
          ];
          inherit shellHook;
        };
        #dsh-overlay-gdc = mkShell {
        #  name = "dub + gdc dev shell";
        #  inherit shell;
        #  inherit devEnv;
        #  packages = [
        #    gnumake
        #    gdc
        #    dub
        #  ];
        #  inherit shellHook;
        #};
        dsh-nixpkgs-ldc-dub = mkShell {
          name = "nixpkgs - ldc - dub";
          inherit shell;
          inherit devEnv;
          packages = with pkgs-nix; [
            ldc
            dub
            gnumake
          ];
          inherit shellHook;
        };
        dsh-nixpkgs-dmd-dub = mkShell {
          name = "nixpkgs - ldc - dub";
          inherit shell;
          inherit devEnv;
          packages = with pkgs-nix; [
            dmd
            dub
            gnumake
          ];
          inherit shellHook;
        };
        default = import ./shell.nix {inherit pkgs-nix;};
      });
  };
}