Merge pull request #535 from matrix-org/rav/paginate_from_stream_token

Make it possible to paginate forwards from stream tokens

synapse/handlers/message.py

@@ -105,8 +105,6 @@ class MessageHandler(BaseHandler):
             room_token = pagin_config.from_token.room_key
 
         room_token = RoomStreamToken.parse(room_token)
-        if room_token.topological is None:
-            raise SynapseError(400, "Invalid token")
 
         pagin_config.from_token = pagin_config.from_token.copy_and_replace(
             "room_key", str(room_token)
@@ -117,9 +115,18 @@ class MessageHandler(BaseHandler):
         membership, member_event_id = yield self._check_in_room_or_world_readable(
             room_id, user_id
         )
+
+        if source_config.direction == 'b':
+            # if we're going backwards, we might need to backfill. This
+            # requires that we have a topo token.
+            if room_token.topological is None:
+                raise SynapseError(400, "Invalid token: cannot paginate "
+                                        "backwards from a stream token")
+
             if membership == Membership.LEAVE:
                 # If they have left the room then clamp the token to be before
-            # they left the room.
+                # they left the room, to save the effort of loading from the
+                # database.
                 leave_token = yield self.store.get_topological_token_for_event(
                     member_event_id
                 )
@@ -127,14 +134,6 @@ class MessageHandler(BaseHandler):
                 if leave_token.topological < room_token.topological:
                     source_config.from_key = str(leave_token)
 
-            if source_config.direction == "f":
-                if source_config.to_key is None:
-                    source_config.to_key = str(leave_token)
-                else:
-                    to_token = RoomStreamToken.parse(source_config.to_key)
-                    if leave_token.topological < to_token.topological:
-                        source_config.to_key = str(leave_token)
-
             yield self.hs.get_handlers().federation_handler.maybe_backfill(
                 room_id, room_token.topological
             )

tests/rest/client/v1/test_rooms.py

@@ -1045,8 +1045,20 @@ class RoomMessageListTestCase(RestTestCase):
         self.assertTrue("end" in response)
 
     @defer.inlineCallbacks
-    def test_stream_token_is_rejected(self):
+    def test_stream_token_is_rejected_for_back_pagination(self):
         (code, response) = yield self.mock_resource.trigger_get(
-            "/rooms/%s/messages?access_token=x&from=s0_0_0_0" %
+            "/rooms/%s/messages?access_token=x&from=s0_0_0_0_0&dir=b" %
             self.room_id)
         self.assertEquals(400, code)
+
+    @defer.inlineCallbacks
+    def test_stream_token_is_accepted_for_fwd_pagianation(self):
+        token = "s0_0_0_0_0"
+        (code, response) = yield self.mock_resource.trigger_get(
+            "/rooms/%s/messages?access_token=x&from=%s" %
+            (self.room_id, token))
+        self.assertEquals(200, code)
+        self.assertTrue("start" in response)
+        self.assertEquals(token, response['start'])
+        self.assertTrue("chunk" in response)
+        self.assertTrue("end" in response)