nixos/displayManager: introduce defaultSession

nixos/doc/manual/configuration/x-windows.xml

@@ -83,8 +83,7 @@
   desktop environment. If you wanted no desktop environment and i3 as your your
   window manager, you'd define:
 <programlisting>
-<xref linkend="opt-services.xserver.desktopManager.default"/> = "none";
-<xref linkend="opt-services.xserver.windowManager.default"/> = "i3";
+<xref linkend="opt-services.xserver.displayManager.defaultSession"/> = "none+i3";
 </programlisting>
   And, finally, to enable auto-login for a user <literal>johndoe</literal>:
 <programlisting>

nixos/doc/manual/configuration/xfce.xml

@@ -7,9 +7,8 @@
  <para>
   To enable the Xfce Desktop Environment, set
 <programlisting>
-<link linkend="opt-services.xserver.desktopManager.default">services.xserver.desktopManager</link> = {
-  <link linkend="opt-services.xserver.desktopManager.xfce.enable">xfce.enable</link> = true;
-  <link linkend="opt-services.xserver.desktopManager.default">default</link> = "xfce";
+<xref linkend="opt-services.xserver.desktopManager.xfce.enable" /> = true;
+<xref linkend="opt-services.xserver.displayManager.defaultSession" /> = "xfce";
 };
 </programlisting>
  </para>

nixos/doc/manual/release-notes/rl-2003.xml

@@ -55,6 +55,19 @@
       and adding a <option>--all</option> option which prints all options and their values.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     <option>services.xserver.desktopManager.default</option> and <option>services.xserver.windowManager.default</option> options were replaced by a single <xref linkend="opt-services.xserver.displayManager.defaultSession"/> option to improve support for upstream session files. If you used something like:
+<programlisting>
+services.xserver.desktopManager.default = "xfce";
+services.xserver.windowManager.default = "icewm";
+</programlisting>
+     you should change it to:
+<programlisting>
+services.xserver.displayManager.defaultSession = "xfce+icewm";
+</programlisting>
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/lib/testing-python.nix

@@ -262,9 +262,8 @@ in rec {
           virtualisation.memorySize = 1024;
           services.xserver.enable = true;
           services.xserver.displayManager.auto.enable = true;
-          services.xserver.windowManager.default = "icewm";
+          services.xserver.displayManager.defaultSession = "none+icewm";
           services.xserver.windowManager.icewm.enable = true;
-          services.xserver.desktopManager.default = "none";
         };
     in
       runInMachine ({

nixos/lib/testing.nix

@@ -249,9 +249,8 @@ in rec {
           virtualisation.memorySize = 1024;
           services.xserver.enable = true;
           services.xserver.displayManager.auto.enable = true;
-          services.xserver.windowManager.default = "icewm";
+          services.xserver.displayManager.defaultSession = "none+icewm";
           services.xserver.windowManager.icewm.enable = true;
-          services.xserver.desktopManager.default = "none";
         };
     in
       runInMachine ({

nixos/modules/programs/sway.nix

@@ -24,6 +24,7 @@ let
   swayJoined = pkgs.symlinkJoin {
     name = "sway-joined";
     paths = [ swayWrapped swayPackage ];
+    passthru.providedSessions = [ "sway" ];
   };
 in {
   options.programs.sway = {
@@ -88,7 +89,7 @@ in {
     fonts.enableDefaultFonts = mkDefault true;
     programs.dconf.enable = mkDefault true;
     # To make a Sway session available if a display manager like SDDM is enabled:
-    services.xserver.displayManager.extraSessionFilePackages = [ swayJoined ];
+    services.xserver.displayManager.sessionPackages = [ swayJoined ];
   };
 
   meta.maintainers = with lib.maintainers; [ gnidorah primeos colemickens ];

nixos/modules/services/x11/desktop-managers/default.nix

@@ -86,23 +86,14 @@ in
       };
 
       default = mkOption {
-        type = types.str;
-        default = "";
+        type = types.nullOr types.str;
+        default = null;
         example = "none";
-        description = "Default desktop manager loaded if none have been chosen.";
-        apply = defaultDM:
-          if defaultDM == "" && cfg.session.list != [] then
-            (head cfg.session.list).name
-          else if any (w: w.name == defaultDM) cfg.session.list then
-            defaultDM
-          else
-            builtins.trace ''
-              Default desktop manager (${defaultDM}) not found at evaluation time.
-              These are the known valid session names:
-                ${concatMapStringsSep "\n  " (w: "services.xserver.desktopManager.default = \"${w.name}\";") cfg.session.list}
-              It's also possible the default can be found in one of these packages:
-                ${concatMapStringsSep "\n  " (p: p.name) config.services.xserver.displayManager.extraSessionFilePackages}
-            '' defaultDM;
+        description = ''
+          <emphasis role="strong">Deprecated</emphasis>, please use <xref linkend="opt-services.xserver.displayManager.defaultSession"/> instead.
+
+          Default desktop manager loaded if none have been chosen.
+        '';
       };
 
     };

nixos/modules/services/x11/desktop-managers/gnome3.nix

@@ -144,7 +144,7 @@ in
       services.gnome3.core-shell.enable = true;
       services.gnome3.core-utilities.enable = mkDefault true;
 
-      services.xserver.displayManager.extraSessionFilePackages = [ pkgs.gnome3.gnome-session ];
+      services.xserver.displayManager.sessionPackages = [ pkgs.gnome3.gnome-session ];
 
       environment.extraInit = ''
         ${concatMapStrings (p: ''
@@ -171,7 +171,7 @@ in
     })
 
     (mkIf flashbackEnabled {
-      services.xserver.displayManager.extraSessionFilePackages =  map
+      services.xserver.displayManager.sessionPackages =  map
         (wm: pkgs.gnome3.gnome-flashback.mkSessionForWm {
           inherit (wm) wmName wmLabel wmCommand;
         }) (optional cfg.flashback.enableMetacity {

nixos/modules/services/x11/desktop-managers/pantheon.nix

@@ -69,7 +69,7 @@ in
 
   config = mkIf cfg.enable {
 
-    services.xserver.displayManager.extraSessionFilePackages = [ pkgs.pantheon.elementary-session-settings ];
+    services.xserver.displayManager.sessionPackages = [ pkgs.pantheon.elementary-session-settings ];
 
     # Ensure lightdm is used when Pantheon is enabled
     # Without it screen locking will be nonfunctional because of the use of lightlocker
@@ -81,9 +81,9 @@ in
 
     services.xserver.displayManager.lightdm.greeters.pantheon.enable = mkDefault true;
 
-    # If not set manually Pantheon session cannot be started
-    # Known issue of https://github.com/NixOS/nixpkgs/pull/43992
-    services.xserver.desktopManager.default = mkForce "pantheon";
+    # Without this, Elementary LightDM greeter will pre-select non-existent `default` session
+    # https://github.com/elementary/greeter/issues/368
+    services.xserver.displayManager.defaultSession = "pantheon";
 
     services.xserver.displayManager.sessionCommands = ''
       if test "$XDG_CURRENT_DESKTOP" = "Pantheon"; then

nixos/modules/services/x11/desktop-managers/surf-display.nix

@@ -118,7 +118,7 @@ in {
   };
 
   config = mkIf cfg.enable {
-    services.xserver.displayManager.extraSessionFilePackages = [
+    services.xserver.displayManager.sessionPackages = [
       pkgs.surf-display
     ];
 

nixos/modules/services/x11/display-managers/account-service-util.nix

@@ -0,0 +1,39 @@
+{ accountsservice
+, glib
+, gobject-introspection
+, python3
+, wrapGAppsHook
+}:
+
+python3.pkgs.buildPythonApplication {
+  name = "set-session";
+
+  format = "other";
+
+  src = ./set-session.py;
+
+  dontUnpack = true;
+
+  strictDeps = false;
+
+  nativeBuildInputs = [
+    wrapGAppsHook
+    gobject-introspection
+  ];
+
+  buildInputs = [
+    accountsservice
+    glib
+  ];
+
+  propagatedBuildInputs = with python3.pkgs; [
+    pygobject3
+    ordered-set
+  ];
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp $src $out/bin/set-session
+    chmod +x $out/bin/set-session
+  '';
+}