gnu: accountsservice: Provide a means to locate extensions.

* gnu/packages/patches/accountsservice-extensions.patch: New patch.
* gnu/packages/freedesktop.scm (accountsservice)[source]: Apply it.
[phases]{wrap-with-xdg-data-dirs}: New phase.

gnu/local.mk

@@ -843,6 +843,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/abseil-cpp-fix-strerror_test.patch	\
   %D%/packages/patches/adb-add-libraries.patch			\
   %D%/packages/patches/adb-libssl_11-compatibility.patch	\
+  %D%/packages/patches/accountsservice-extensions.patch		\
   %D%/packages/patches/aegis-constness-error.patch         	\
   %D%/packages/patches/aegis-perl-tempdir1.patch           	\
   %D%/packages/patches/aegis-perl-tempdir2.patch           	\

gnu/packages/freedesktop.scm

@@ -1443,7 +1443,8 @@ (define-public accountsservice
                            "accountsservice/accountsservice-"
                            version ".tar.xz"))
        (sha256
-        (base32 "14d3lwik048h62qrzg1djdd2sqmxf3m1r859730pvzhrd6krg6ch"))))
+        (base32 "14d3lwik048h62qrzg1djdd2sqmxf3m1r859730pvzhrd6krg6ch"))
+       (patches (search-patches "accountsservice-extensions.patch"))))
     (build-system meson-build-system)
     (arguments
      `(#:configure-flags
@@ -1479,7 +1480,14 @@ (define-public accountsservice
                (("/usr/bin/passwd")
                 (search-input-file inputs "bin/passwd"))
                (("/usr/bin/chage")
-                (search-input-file inputs "bin/chage"))))))))
+                (search-input-file inputs "bin/chage")))))
+         (add-after 'install 'wrap-with-xdg-data-dirs
+           ;; This is to allow accountsservice finding extensions, which
+           ;; should be installed to the system profile.
+           (lambda* (#:key outputs #:allow-other-keys)
+             (wrap-program (search-input-file outputs "libexec/accounts-daemon")
+               '("XDG_DATA_DIRS" prefix
+                 ("/run/current-system/profile/share"))))))))
     (native-inputs
      (list docbook-xml-4.1.2
            docbook-xsl

gnu/packages/patches/accountsservice-extensions.patch

@@ -0,0 +1,25 @@
+Patch from NixOS retrieved from
+https://raw.githubusercontent.com/NixOS/nixpkgs/master/pkgs/development/libraries/accountsservice/drop-prefix-check-extensions.patch.
+
+diff --git a/src/extensions.c b/src/extensions.c
+index 038dcb2..830465d 100644
+--- a/src/extensions.c
++++ b/src/extensions.c
+@@ -121,16 +121,7 @@ daemon_read_extension_directory (GHashTable  *ifaces,
+                         continue;
+                 }
+ 
+-                /* Ensure it looks like "../../dbus-1/interfaces/${name}" */
+-                const gchar * const prefix = "../../dbus-1/interfaces/";
+-                if (g_str_has_prefix (symlink, prefix) && g_str_equal (symlink + strlen (prefix), name)) {
+-                        daemon_read_extension_file (ifaces, filename);
+-                }
+-                else {
+-                        g_warning ("Found accounts service vendor extension symlink %s, but it must be exactly "
+-                                   "equal to '../../dbus-1/interfaces/%s' for forwards-compatibility reasons.",
+-                                   filename, name);
+-                }
++                daemon_read_extension_file (ifaces, filename);
+         }
+ 
+         g_dir_close (dir);