Contrary to what I said, the warning also appear on previous versions, and with online contacts.

The object gabble_im_channel_class contains 5 properties: connection,
object-path, handle, channel-type and handle-type. But only 3 are initialized
here:

im-factory.c:new_im_channel():
  chan = g_object_new (GABBLE_TYPE_IM_CHANNEL,
                       "connection", priv->conn,
                       "object-path", object_path,
                       "handle", handle,
                       NULL);

g_object_new() calls the constructor with properties as parameters:

gabble-im-channel.c:gabble_im_channel_constructor():
  gabble_im_channel_constructor (GType type, guint n_props,
                                 GObjectConstructParam *props)
  {
    [...]
    obj = G_OBJECT_CLASS (gabble_im_channel_parent_class)->
             constructor (type, n_props, props);

However, the constructor receives values for all 5 properties, and not only the
3 from g_object_new(), because according to (*), construction parameters which
are not explicitly specified are set to their default values.

(*) http://library.gnome.org/devel/gobject/unstable/gobject-The-Base-Object-Type.html#g-object-new

The warning can be removed with:

--- old-telepathy-gabble-cassidy/src/gabble-im-channel.c        2008-01-02 22:24:50.000000000 +0100
+++ new-telepathy-gabble-cassidy/src/gabble-im-channel.c        2008-01-02 22:24:50.000000000 +0100
@@ -180,6 +180,12 @@
       g_free (priv->object_path);
       priv->object_path = g_value_dup_string (value);
       break;
+    case PROP_CHANNEL_TYPE:
+      /* The channel type is a constant: TP_IFACE_CHANNEL_TYPE_TEXT and must
+       * not be changed. However, g_object_new() set all properties, so we get
+       * called to change the property PROP_CHANNEL_TYPE.
+       */
+      break;
     case PROP_HANDLE:
       /* we don't ref it here because we don't necessarily have access to the
        * contact repo yet - instead we ref it in the constructor.

This warning is fairly harmless; it's caused by having a bleeding-edge version of telepathy-glib, which changes the channel type from read-only to read/write. The other GLib connection managers will have the same bug. I'll make sure to fix them all before releasing the current darcs telepathy-glib.

Note that darcs versions of telepathy-glib have no API or ABI stability guarantees - we only guarantee that ABI will not be broken once it has appeared in a release of telepathy-glib. You'll have to recompile (or at least relink) Empathy and any other locally compiled Telepathy components when you upgrade to a released version of telepathy-glib.

Created attachment 13516 [details] [review]
You need no-op code similar to this in the _set_property callback of each TpChannelIface implementation

Fixed in darcs for Gabble, Salut, Haze. Similar patches queued for review for Idle and telepathy-sofiasip, and I'll file a bug against gnome-phone-manager.

If anyone else encounters this problem, the solution is to check all your implementations of TpChannelIface to make sure they won't warn when the channel-type property is written. Having the set callback be a no-op for the channel type, like it often already is for the handle type, is the simplest solution (see attached).

The same bug in gnome-phone-manager: http://bugzilla.gnome.org/show_bug.cgi?id=507258

Merged to idle darcs head.

OK, I think we've fixed this in HEAD of all the CMs...