Add apps

all-modules.nix

@@ -1,6 +1,7 @@
 { lib, ... }:
 {
   imports = [
+    ./modules/apps.nix
     ./modules/checks.nix
     ./modules/darwinModules.nix
     ./modules/devShells.nix

modules/apps.nix

@@ -0,0 +1,91 @@
+{ config, lib, flake-modules-core-lib, ... }:
+let
+  inherit (lib)
+    filterAttrs
+    mapAttrs
+    mkOption
+    optionalAttrs
+    types
+    ;
+  inherit (flake-modules-core-lib)
+    mkSubmoduleOptions
+    ;
+
+  programType = lib.types.coercedTo lib.types.package getExe lib.types.str;
+
+  getExe = x:
+    "${lib.getBin x}/bin/${x.meta.mainProgram or (throw ''Package ${x.name or ""} does not have meta.mainProgram set, so I don't know how to find the main executable. You can set meta.mainProgram, or pass the full path to executable, e.g. program = "''${pkg}/bin/foo"'')}";
+
+  getBin = x:
+    if !x?outputSpecified || !x.outputSpecified
+      then x.bin or x.out or x
+      else x;
+
+  appType = lib.types.submodule {
+    options = {
+      type = mkOption {
+        type = lib.types.enum ["app"];
+        default = "app";
+        description = ''
+          A type tag for <literal>apps</literal> consumers.
+        '';
+      };
+      program = mkOption {
+        type = programType;
+        description = ''
+          A path to an executable or a derivation with <literal>meta.mainProgram</literal>.
+        '';
+      };
+    };
+  };
+in
+{
+  options = {
+    flake = mkSubmoduleOptions {
+      apps = mkOption {
+        type = types.lazyAttrsOf (types.lazyAttrsOf appType);
+        default = { };
+        description = ''
+          Programs runnable with nix run <literal>.#&lt;name></literal>.
+        '';
+        example = lib.literalExample ''
+          {
+            x86_64-linux.default.program = "''${config.packages.hello}/bin/hello";
+          }
+        '';
+      };
+    };
+  };
+  config = {
+    flake.apps =
+      mapAttrs
+        (k: v: v.apps)
+        (filterAttrs
+          (k: v: v.apps != null)
+          config.allSystems
+        );
+
+    perInput = system: flake:
+      optionalAttrs (flake?apps.${system}) {
+        apps = flake.apps.${system};
+      };
+
+    perSystem = system: { config, ... }: {
+      _file = ./apps.nix;
+      options = {
+        apps = mkOption {
+          type = types.lazyAttrsOf appType;
+          default = { };
+          description = ''
+            Programs runnable with nix run <literal>.#&lt;name></literal>.
+          '';
+          example = lib.literalExample ''
+            {
+              default.program = "''${config.packages.hello}/bin/hello";
+            }
+          '';
+        };
+      };
+    };
+  };
+}