darkman: allow no configuration

Closes #4779

Signed-off-by: Sumner Evans <me@sumnerevans.com>

modules/services/darkman.nix

@@ -52,6 +52,7 @@ in {
 
     settings = mkOption {
       type = types.submodule { freeformType = yamlFormat.type; };
+      default = { };
       example = literalExpression ''
         {
           lat = 52.3;
@@ -96,7 +97,7 @@ in {
         Documentation = "man:darkman(1)";
         PartOf = [ "graphical-session.target" ];
         BindsTo = [ "graphical-session.target" ];
-        X-Restart-Triggers =
+        X-Restart-Triggers = mkIf (cfg.settings != { })
           [ "${config.xdg.configFile."darkman/config.yaml".source}" ];
       };
 

tests/modules/services/darkman/default.nix

@@ -1 +1,4 @@
-{ darkman-basic-configuration = ./basic-configuration.nix; }
+{
+  darkman-basic-configuration = ./basic-configuration.nix;
+  darkman-no-configuration = ./no-configuration.nix;
+}

tests/modules/services/darkman/no-configuration.nix

@@ -0,0 +1,37 @@
+{
+  services.darkman.enable = true;
+
+  test.stubs = {
+    python = { };
+    darkman = { };
+  };
+
+  nmt.script = ''
+    serviceFile=$(normalizeStorePaths home-files/.config/systemd/user/darkman.service)
+
+    assertFileExists $serviceFile
+    assertFileContent $serviceFile ${
+      builtins.toFile "expected" ''
+        [Install]
+        WantedBy=graphical-session.target
+
+        [Service]
+        BusName=nl.whynothugo.darkman
+        ExecStart=@darkman@/bin/dummy run
+        Restart=on-failure
+        Slice=background.slice
+        TimeoutStopSec=15
+        Type=dbus
+
+        [Unit]
+        BindsTo=graphical-session.target
+        Description=Darkman system service
+        Documentation=man:darkman(1)
+        PartOf=graphical-session.target
+      ''
+    }
+    assertPathNotExists home-files/.local/share/dark-mode.d/color-scheme-dark
+    assertPathNotExists home-files/.local/share/light-mode.d/color-scheme-light
+  '';
+}
+