pass old roster to roster update callback

source/Network/Xmpp/Concurrent.hs

@@ -188,7 +188,7 @@ newSession stream config realm mbSasl = runErrorT $ do
     boundJid <- liftIO $ withStream' (gets streamJid) stream
     let rosterH = if (enableRoster config)
                   then [handleRoster boundJid rosRef
-                          (fromMaybe (\_ -> return ()) $ onRosterPush config)
+                          (fromMaybe (\_ _ -> return ()) $ onRosterPush config)
                           (out)]
                   else []
     let presenceH = if (enablePresenceTracking config)

source/Network/Xmpp/Concurrent/Types.hs

@@ -70,7 +70,7 @@ type Plugin = (XmppElement -> IO (Either XmppFailure ())) -- ^ pass stanza to
                                                           -- next plugin
               -> ErrorT XmppFailure IO Plugin'
 
-type RosterPushCallback = RosterUpdate -> IO ()
+type RosterPushCallback = Roster -> RosterUpdate -> IO ()
 
 -- | Configuration for the @Session@ object.
 data SessionConfiguration = SessionConfiguration

source/Network/Xmpp/IM/Roster.hs

@@ -133,15 +133,16 @@ handleRoster mbBoundJid ref onUpdate out sta _ = do
                     else return [(sta, [])]
         _ -> return [(sta, [])]
   where
-    handleUpdate v' update =
+    handleUpdate v' update = do
+        oldRoster <- atomically $ readTVar ref
         case qiSubscription update of
          Just Remove -> do
              let j = qiJid update
-             onUpdate $ RosterUpdateRemove j
+             onUpdate oldRoster $ RosterUpdateRemove j
              updateRoster (Map.delete j)
          _ -> do
              let i = (toItem update)
-             onUpdate $ RosterUpdateAdd i
+             onUpdate oldRoster $ RosterUpdateAdd i
              updateRoster $ Map.insert (qiJid update) i
       where
         updateRoster f = atomically . modifyTVar ref $