emacs: add darwin service

modules/services/emacs.nix

@@ -1,9 +1,6 @@
 { config, lib, pkgs, ... }:
-
 with lib;
-
 let
-
   cfg = config.services.emacs;
   emacsCfg = config.programs.emacs;
   emacsBinPath = "${cfg.package}/bin";
@@ -41,7 +38,6 @@ let
   # to work without wrapping it.
   socketDir = "%t/emacs";
   socketPath = "${socketDir}/server";
-
 in {
   meta.maintainers = [ maintainers.tadfisher ];
 
@@ -112,12 +108,7 @@ in {
   };
 
   config = mkIf cfg.enable (mkMerge [
-    {
+    (mkIf pkgs.stdenv.isLinux {
-      assertions = [
-        (lib.hm.assertions.assertPlatform "services.emacs" pkgs
-          lib.platforms.linux)
-      ];
-
       systemd.user.services.emacs = {
         Unit = {
           Description = "Emacs text editor";
@@ -190,9 +181,9 @@ in {
             }/bin/emacsclient "''${@:---create-frame}"'');
         };
       };
-    }
+    })
 
-    (mkIf cfg.socketActivation.enable {
+    (mkIf (cfg.socketActivation.enable && pkgs.stdenv.isLinux) {
       systemd.user.sockets.emacs = {
         Unit = {
           Description = "Emacs text editor";
@@ -222,5 +213,20 @@ in {
         };
       };
     })
+
+    (mkIf pkgs.stdenv.isDarwin {
+      launchd.agents.emacs = {
+        enable = true;
+        config = {
+          ProgramArguments = [ "${cfg.package}/bin/emacs" "--fg-daemon" ]
+            ++ cfg.extraOptions;
+          RunAtLoad = true;
+          KeepAlive = {
+            Crashed = true;
+            SuccessfulExit = false;
+          };
+        };
+      };
+    })
   ]);
 }