gdbusconnection: Support matching object paths with arg0 matching

GDBus has always supported matching strings with arg0 matching (G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_PATH). In D-Bus 1.5, support was added to the spec for also matching object paths. This got forgotten about and was never added to GDBus, meaning that G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_PATH won’t match against a signal arg0 of type o.

Fix that, and add a unit test.

To do so, we need to add a new g_dbus_message_get_arg0_path() API to complement the existing g_dbus_message_get_arg0() API. The approach of letting g_dbus_message_get_arg0() return an object-path or a string would not work, as it’s also called in the implementation of G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_NAMESPACE, which must only match string-typed arg0 values and not object-path-typed ones.

Signed-off-by: Philip Withnall pwithnall@gnome.org

Fixes: #3183 (closed)

Closes #3183 (closed)