From 9bcb49ea48ae5f26a6ffa3d1eddf25826a76df7e Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Tue, 18 Aug 2020 09:23:44 -0400
Subject: [PATCH] Fix the return type of send_nonmember_events.

---
 changelog.d/8112.misc                    |  1 +
 synapse/handlers/message.py              |  2 +-
 synapse/storage/databases/main/stream.py | 19 +++++++++++++++----
 3 files changed, 17 insertions(+), 5 deletions(-)
 create mode 100644 changelog.d/8112.misc

diff --git a/changelog.d/8112.misc b/changelog.d/8112.misc
new file mode 100644
index 000000000000..80045dde1af1
--- /dev/null
+++ b/changelog.d/8112.misc
@@ -0,0 +1 @@
+Return the previous stream token if a non-member event is a duplicate.
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index f242d3c6acb7..532fc30681b0 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -674,7 +674,7 @@ async def send_nonmember_event(
                     event.event_id,
                     prev_event.event_id,
                 )
-                return await self.store.get_stream_token_for_event(prev_event.event_id)
+                return await self.store.get_stream_id_for_event(prev_event.event_id)
 
         return await self.handle_new_client_event(
             requester=requester, event=event, context=context, ratelimit=ratelimit
diff --git a/synapse/storage/databases/main/stream.py b/synapse/storage/databases/main/stream.py
index 8ccfb8fc46f6..4377bddb8cae 100644
--- a/synapse/storage/databases/main/stream.py
+++ b/synapse/storage/databases/main/stream.py
@@ -582,6 +582,19 @@ async def get_room_events_max_id(self, room_id: Optional[str] = None) -> str:
             )
             return "t%d-%d" % (topo, token)
 
+    async def get_stream_id_for_event(self, event_id: str) -> int:
+        """The stream ID for an event
+        Args:
+            event_id: The id of the event to look up a stream token for.
+        Raises:
+            StoreError if the event wasn't in the database.
+        Returns:
+            A stream ID.
+        """
+        return await self.db_pool.simple_select_one_onecol(
+            table="events", keyvalues={"event_id": event_id}, retcol="stream_ordering"
+        )
+
     async def get_stream_token_for_event(self, event_id: str) -> str:
         """The stream token for an event
         Args:
@@ -591,10 +604,8 @@ async def get_stream_token_for_event(self, event_id: str) -> str:
         Returns:
             A "s%d" stream token.
         """
-        row = await self.db_pool.simple_select_one_onecol(
-            table="events", keyvalues={"event_id": event_id}, retcol="stream_ordering"
-        )
-        return "s%d" % (row,)
+        stream_id = await self.get_stream_id_for_event(event_id)
+        return "s%d" % (stream_id,)
 
     async def get_topological_token_for_event(self, event_id: str) -> str:
         """The stream token for an event