Use the filtered version of an event when responding to /context requests for that event

Sometimes the filtering function can return a pruned version of an event (on top of either the event itself or an empty list), if it thinks the user should be able to see that there's an event there but not the content of that event. Therefore, the previous logic of 'if filtered is empty then we can use the event we retrieved from the database' is flawed, and we should use the event returned by the filtering function.

1 files changed, 4 insertions, 1 deletions

diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 22768e97ff..7f979e5812 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -907,7 +907,10 @@ class RoomContextHandler(object):
 
         results["events_before"] = yield filter_evts(results["events_before"])
         results["events_after"] = yield filter_evts(results["events_after"])
-        results["event"] = event
+        # filter_evts can return a pruned event in case the user is allowed to see that
+        # there's something there but not see the content, so use the event that's in
+        # `filtered` rather than the event we retrieved from the datastore.
+        results["event"] = filtered[0]
 
         if results["events_after"]:
             last_event_id = results["events_after"][-1].event_id