Review comments

synapse/handlers/_base.py

@@ -222,7 +222,8 @@ class BaseHandler(object):
             if event_type == EventTypes.Member
         ]
         if len(room_members) == 0:
-            # has the room been created so we can join it?
+            # Have we just created the room, and is this about to be the very
+            # first member event?
             create_event = current_state.get(("m.room.create", ""))
             if create_event:
                 return True

synapse/handlers/message.py

@@ -229,7 +229,7 @@ class MessageHandler(BaseHandler):
         if event.type == EventTypes.Member:
             raise SynapseError(
                 500,
-                "Tried to send member even through non-member codepath"
+                "Tried to send member event through non-member codepath"
             )
 
         user = UserID.from_string(event.sender)

synapse/handlers/room.py

@@ -490,11 +490,10 @@ class RoomMemberHandler(BaseHandler):
             sender = UserID.from_string(event.sender)
             assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
 
-        if event.is_state():
-            message_handler = self.hs.get_handlers().message_handler
-            prev_event = message_handler.deduplicate_state_event(event, context)
-            if prev_event is not None:
-                return
+        message_handler = self.hs.get_handlers().message_handler
+        prev_event = message_handler.deduplicate_state_event(event, context)
+        if prev_event is not None:
+            return
 
         action = "send"