targets.darwin: add module

Currently, this module makes sure that `/Applications` directories for
packages in `home.packages` get linked into the user's environment.

modules/modules.nix

@@ -189,6 +189,7 @@ let
     (loadModule ./services/xscreensaver.nix { })
     (loadModule ./services/xsuspender.nix { condition = hostPlatform.isLinux; })
     (loadModule ./systemd.nix { })
+    (loadModule ./targets/darwin.nix { condition = hostPlatform.isDarwin; })
     (loadModule ./targets/generic-linux.nix { condition = hostPlatform.isLinux; })
     (loadModule ./xcursor.nix { })
     (loadModule ./xresources.nix { })

modules/targets/darwin.nix

@@ -0,0 +1,14 @@
+{ config, lib, pkgs, ... }:
+
+{
+  config = lib.mkIf pkgs.stdenv.hostPlatform.isDarwin {
+    # Install MacOS applications to the user environment.
+    home.file."Applications/Home Manager Apps".source = let
+      apps = pkgs.buildEnv {
+        name = "home-manager-applications";
+        paths = config.home.packages;
+        pathsToLink = "/Applications";
+      };
+    in "${apps}/Applications";
+  };
+}

tests/default.nix

@@ -69,6 +69,8 @@ import nmt {
     ./modules/programs/zplug
     ./modules/programs/zsh
     ./modules/xresources
+  ] ++ lib.optionals pkgs.stdenv.hostPlatform.isDarwin [
+    ./modules/targets-darwin
   ] ++ lib.optionals pkgs.stdenv.hostPlatform.isLinux [
     ./meta # Suffices to run on one platform.
     ./modules/misc/debug
@@ -93,6 +95,6 @@ import nmt {
     ./modules/services/window-managers/i3
     ./modules/services/window-managers/sway
     ./modules/systemd
-    ./modules/targets
+    ./modules/targets-linux
   ]);
 }

tests/modules/targets-darwin/darwin.nix

@@ -0,0 +1,20 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  darwinTestApp = pkgs.runCommandLocal "target-darwin-example-app" { } ''
+    mkdir -p $out/Applications
+    touch $out/Applications/example-app
+  '';
+
+in {
+  config = {
+    home.packages = [ darwinTestApp ];
+
+    nmt.script = ''
+      assertFileExists 'home-files/Applications/Home Manager Apps/example-app'
+    '';
+  };
+}

tests/modules/targets-darwin/default.nix

@@ -0,0 +1 @@
+{ targets-darwin = ./darwin.nix; }