Don't assume RoomStreamTokens can be compared

synapse/types.py

@@ -413,6 +413,18 @@ def parse_stream_token(cls, string: str) -> "RoomStreamToken":
             pass
         raise SynapseError(400, "Invalid token %r" % (string,))
 
+    def copy_and_advance(self, other: "RoomStreamToken") -> "RoomStreamToken":
+        """Return a new token such that if an event is after both this token and
+        the other token, then its after the returned token too.
+        """
+
+        if self.topological or other.topological:
+            raise Exception("Can't advance topological tokens")
+
+        max_stream = max(self.stream, other.stream)
+
+        return RoomStreamToken(None, max_stream)
+
     def as_tuple(self) -> Tuple[Optional[int], int]:
         return (self.topological, self.stream)
 
@@ -462,13 +474,16 @@ def copy_and_advance(self, key, new_value) -> "StreamToken":
         """Advance the given key in the token to a new value if and only if the
         new value is after the old value.
         """
-        new_token = self.copy_and_replace(key, new_value)
         if key == "room_key":
-            new_id = new_token.room_stream_id
-            old_id = self.room_stream_id
-        else:
-            new_id = int(getattr(new_token, key))
-            old_id = int(getattr(self, key))
+            new_token = self.copy_and_replace(
+                "room_key", self.room_key.copy_and_advance(new_value)
+            )
+            return new_token
+
+        new_token = self.copy_and_replace(key, new_value)
+        new_id = int(getattr(new_token, key))
+        old_id = int(getattr(self, key))
+
         if old_id < new_id:
             return new_token
         else: