gnu: Split gnome into more meta-packages.

* gnu/packages/gnome.scm (gnome-meta-package): New syntax rule.
(gnome-meta-core-services, gnome-meta-core-shell, gnome-meta-core-utilities)
(gnome-essential-extras): New variables.
(gnome): Implement in terms of the former.

gnu/packages/gnome.scm

@@ -10154,27 +10154,47 @@ world.")
     (home-page "https://wiki.gnome.org/Apps/Weather")
     (license license:gpl2+)))
 
-(define-public gnome
+(define-syntax gnome-meta-package
+  (lambda (x)
+    (syntax-case x ()
+      ((_ field ...)
+       (with-syntax ((base (datum->syntax x 'base)))
+         #'(let ((base
                   (package
-    (name "gnome")
+                    (name #f)      ; we're hidden by default, so don't worry
                     (version (package-version gnome-shell))
                     (source #f)
                     (build-system trivial-build-system)
-    (arguments '(#:builder (begin (mkdir %output) #t)))
+                    (arguments
-    (propagated-inputs
+                     (list #:builder
-     `(,@(if (string-prefix? "x86_64" (%current-system))
+                           #~(begin (format (current-warning-port)
-             ;; XXX: EoG requires librsvg-next, which depends on Rust, which currently
+                                            "Building ~a is useless.  \
-             ;; only works on x86_64, so exclude it on other architectures.
+Refer to its propagated inputs instead.\n"
-             (list eog)
+                                            #$(package-name this-package))
-             '())
+                                    (mkdir #$output))))
-       ,@(list
+                    (home-page "https://www.gnome.org")
-          ;; GNOME-Core-OS-Services.
+                    (synopsis "The GNU desktop environment")
-          accountsservice
+                    (description "\
+GNOME is the graphical desktop for GNU.  It includes a wide variety of
+applications for browsing the web, editing text and images, creating
+documents and diagrams, playing media, scanning, and much more.")
+                    (license license:gpl2+)
+                    (properties `((hidden? . #t))))))
+             (package (inherit base)
+                      field ...)))))))
+
+(define-public gnome-meta-core-services
+  (gnome-meta-package
+   (name "gnome-meta-core-services")
+   (propagated-inputs (list accountsservice
                             network-manager
                             packagekit
-          upower
+                            upower))))
-          ;; GNOME-Core-Shell.
+
-          adwaita-icon-theme
+(define-public gnome-meta-core-shell
+  (gnome-meta-package
+   (name "gnome-meta-core-shell")
+   (propagated-inputs (list adwaita-icon-theme
                             gdm
                             glib-networking
                             gnome-backgrounds
@@ -10197,9 +10217,19 @@ world.")
                             mutter
                             orca
                             rygel
-          sushi
+                            sushi))))
-          ;; GNOME-Core-Utilities.
+
-          baobab
+(define-public gnome-meta-core-utilities
+  (gnome-meta-package
+   (name "gnome-meta-core-utilities")
+   (propagated-inputs
+    (append
+     ;; XXX: EoG requires librsvg-next, which depends on Rust, which currently
+     ;; only works on x86_64, so exclude it on other architectures.
+     (if (string-prefix? "x86_64" (%current-system))
+         (list eog)
+         '())
+     (list baobab
            cheese
            epiphany
            evince
@@ -10224,38 +10254,44 @@ world.")
            totem
            tracker-miners
            xdg-desktop-portal-gnome
-          yelp
+           yelp)))))
-          ;; Others.
-          gnome-online-accounts
-          hicolor-icon-theme
 
-          ;; Packages not part of GNOME proper but that are needed for a good
+(define-public gnome-essential-extras
-          ;; experience.  See <https://bugs.gnu.org/39646>.
+  (gnome-meta-package
-          ;; XXX: Find out exactly which ones are needed and why.
+   (name "gnome-essential-extras")
-          at-spi2-core
+   (propagated-inputs (list at-spi2-core
                             dbus
                             dconf
                             desktop-file-utils
                             font-abattis-cantarell
                             font-dejavu
                             gnome-default-applications
+                            gnome-online-accounts
                             gst-plugins-base
                             gst-plugins-good
                             gucharmap
+                            hicolor-icon-theme
                             pinentry-gnome3
                             pulseaudio
                             shared-mime-info
                             system-config-printer
                             xdg-user-dirs
                             yelp
-          zenity)))
+                            zenity))
-    (synopsis "The GNU desktop environment")
+   (description "This package provides a list of packages required for
-    (home-page "https://www.gnome.org/")
+a good GNOME experience, mixed from core dependencies and other implicitly
-    (description
+relied-on packages.")))
-     "GNOME is the graphical desktop for GNU.  It includes a wide variety of
+
-applications for browsing the web, editing text and images, creating
+(define-public gnome
-documents and diagrams, playing media, scanning, and much more.")
+  (gnome-meta-package
-    (license license:gpl2+)))
+   (name "gnome")
+   (propagated-inputs
+    (append-map package-propagated-inputs
+                (list gnome-meta-core-services
+                      gnome-meta-core-shell
+                      gnome-meta-core-utilities
+                      gnome-essential-extras)))
+   (properties (list))))
 
 (define-public byzanz
   ;; The last stable release of Byzanz was in 2011, but there have been many