nixos/programs/gnome-session: refactor and update module

modules/nixos/programs/gnome-session/default.nix

@@ -60,27 +60,16 @@ let
             '';
           };
 
-        installDesktopSessions = builtins.map
+        installDesktopSessionFiles = builtins.map
           (display:
             displayScripts.${display})
           session.display;
 
-        installDesktops =
+        installDesktopFiles =
           lib.mapAttrsToList
             (name: component:
               let
-                scriptName = "${session.name}-${component.name}-script";
-
-                # There's already a lot of bad bad things in this world, we
-                # don't to add more of it here (only a fraction of it, though).
-                scriptPackage = pkgs.writeShellApplication {
-                  name = scriptName;
-                  text = component.script;
-                };
-
-                script = "${scriptPackage}/bin/${scriptName}";
-                desktopConfig = lib.mergeAttrs component.desktopConfig { exec = script; };
-                desktopPackage = pkgs.makeDesktopItem desktopConfig;
+                desktopPackage = pkgs.makeDesktopItem component.desktopConfig;
               in
               ''
                 install -Dm0644 ${desktopPackage}/share/applications/*.desktop -t $out/share/applications
@@ -105,9 +94,9 @@ let
           install -Dm0644 "$gnomeSessionPath" "$GNOME_SESSION_FILE"
           substituteAllInPlace "$GNOME_SESSION_FILE"
 
-          ${lib.concatStringsSep "\n" installDesktopSessions}
+          ${lib.concatStringsSep "\n" installDesktopSessionFiles}
 
-          ${lib.concatStringsSep "\n" installDesktops}
+          ${lib.concatStringsSep "\n" installDesktopFiles}
         ''
     )
     cfg.sessions;

modules/nixos/programs/gnome-session/submodules/component-type.nix

@@ -1,4 +1,4 @@
-{ name, config, lib, utils, session, ... }:
+{ name, config, pkgs, lib, utils, session, ... }:
 
 let
   optionalSystemdUnitOption = type: systemdModuleAttribute:
@@ -29,14 +29,22 @@ in
     description = lib.mkOption {
       type = lib.types.nonEmptyStr;
       description = "One-sentence description of the component.";
+      default = name;
       example = "Desktop widgets";
     };
 
     script = lib.mkOption {
       type = lib.types.lines;
       description = ''
-        Shell script fragment of the component. Take note this will be
-        wrapped in a script for proper integration with `gnome-session`.
+        Shell script fragment of the component.
+
+        The way it is handled is different per startup methods.
+
+        * This will be wrapped in a script for proper integration with the
+        legacy non-systemd session management.
+
+        * For systemd-managed sessions, it will be part of
+        {option}`programs.gnome-session.sessions.<sessions>.components.<name>.serviceUnit.script`.
       '';
     };
 
@@ -182,6 +190,7 @@ in
     desktopConfig = {
       name = lib.mkForce config.id;
       desktopName = lib.mkDefault "${session.fullName} - ${config.description}";
+      exec = lib.mkDefault (pkgs.writeShellScript "${session.name}-${config.name}-script" config.script);
       noDisplay = lib.mkForce true;
       onlyShowIn = session.desktopNames;
 
@@ -213,7 +222,6 @@ in
       NixOS-module-generated gnome-session sessions so we're not bothering with
       those.
 
-      TODO: Is `Type=notify` a good default?
       * `Service.Type=` is obviously not included since not all desktop
       components are the same either. Some of them could be a D-Bus service,
       some of them are oneshots, etc. Though, it might be better to have this

modules/nixos/programs/gnome-session/submodules/session-type.nix

@@ -162,6 +162,7 @@ in
         customized version of GNOME.
         :::
       '';
+      default = lib.mapAttrsToList (_: component: component.id) config.components;
       example = [
         "org.gnome.Shell"
         "org.gnome.SettingsDaemon.A11ySettings"
@@ -210,10 +211,6 @@ in
     # Append the session argument.
     extraArgs = [ "--session=${name}" ];
 
-    # By default. set the required components from the given desktop
-    # components.
-    requiredComponents = lib.mapAttrsToList (_: component: component.id) config.components;
-
     targetUnit = {
       overrideStrategy = lib.mkForce "asDropin";
       wants = lib.mkDefault (builtins.map (c: "${c}.target") config.requiredComponents);