Merge branch '3559-revert-dbus-method-invocation-refcounting' into 'main'

Revert "gdbus: Fix leak of method invocation when registering an object with closures"

Closes #3559

See merge request GNOME/glib!4427

gio/gdbusconnection.c

@@ -5951,7 +5951,12 @@ register_with_closures_on_method_call (GDBusConnection       *connection,
   g_value_set_variant (&params[5], parameters);
 
   g_value_init (&params[6], G_TYPE_DBUS_METHOD_INVOCATION);
-  g_value_take_object (&params[6], g_steal_pointer (&invocation));
+  /* NOTE: This is deliberately *not* g_value_take_object(). A reference to
+   * `invocation` is transferred in to this function, and it needs to be
+   * transferred onwards to the `g_dbus_method_invocation_return_*()` method
+   * call which must eventually happen (either in the closure function, or in
+   * a delayed consequence from it). Changing this will break API. */
+  g_value_set_object (&params[6], invocation);
 
   g_closure_invoke (data->method_call_closure, NULL, G_N_ELEMENTS (params), params, NULL);
 
@@ -6085,6 +6090,11 @@ register_with_closures_on_set_property (GDBusConnection *connection,
  * Version of g_dbus_connection_register_object() using closures instead of a
  * #GDBusInterfaceVTable for easier binding in other languages.
  *
+ * Note that the reference counting semantics of the function wrapped by
+ * @method_call_closure are the same as those of
+ * [callback@Gio.DBusInterfaceMethodCallFunc]: ownership of a reference to the
+ * [class@Gio.DBusMethodInvocation] is transferred to the function.
+ *
  * Returns: 0 if @error is set, otherwise a registration ID (never 0)
  * that can be used with g_dbus_connection_unregister_object() .
  *