nixos/gnome: make it possible to remove core packages

Co-Authored-By: Jan Tojnar <jtojnar@gmail.com>

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

@@ -403,10 +403,17 @@ in
     })
 
     (mkIf serviceCfg.core-shell.enable {
-      services.xserver.desktopManager.gnome.sessionPath = [
+      services.xserver.desktopManager.gnome.sessionPath =
+        let
+          mandatoryPackages = [
             pkgs.gnome.gnome-shell
+          ];
+          optionalPackages = [
             pkgs.gnome.gnome-shell-extensions
           ];
+        in
+        mandatoryPackages
+        ++ utils.removePackagesByName optionalPackages config.environment.gnome.excludePackages;
 
       services.colord.enable = mkDefault true;
       services.gnome.chrome-gnome-shell.enable = mkDefault true;
@@ -460,24 +467,31 @@ in
       ];
 
       # Adapt from https://gitlab.gnome.org/GNOME/gnome-build-meta/blob/gnome-3-38/elements/core/meta-gnome-core-shell.bst
-      environment.systemPackages = with pkgs.gnome; [
+      environment.systemPackages =
+        let
+          mandatoryPackages = with pkgs.gnome; [
+            gnome-shell
+          ];
+          optionalPackages = with pkgs.gnome; [
             adwaita-icon-theme
             nixos-background-info
             gnome-backgrounds
             gnome-bluetooth
             gnome-color-manager
             gnome-control-center
-        gnome-shell
             gnome-shell-extensions
             gnome-themes-extra
             pkgs.gnome-tour # GNOME Shell detects the .desktop file on first log-in.
             pkgs.gnome-user-docs
             pkgs.orca
-        pkgs.glib # for gsettings
+            pkgs.glib # for gsettings program
             pkgs.gnome-menus
-        pkgs.gtk3.out # for gtk-launch
+            pkgs.gtk3.out # for gtk-launch program
             pkgs.xdg-user-dirs # Update user dirs as described in http://freedesktop.org/wiki/Software/xdg-user-dirs/
           ];
+        in
+        mandatoryPackages
+        ++ utils.removePackagesByName optionalPackages config.environment.gnome.excludePackages;
     })
 
     # Adapt from https://gitlab.gnome.org/GNOME/gnome-build-meta/blob/gnome-3-38/elements/core/meta-gnome-core-utilities.bst