show heroes if a room has deleted name/canonical_alias

changelog.d/3851.bugfix

@@ -0,0 +1 @@
+Show heroes if room name/canonical alias has been deleted

synapse/handlers/sync.py

@@ -562,8 +562,21 @@ def compute_summary(self, room_id, sync_config, batch, state, now_token):
  details.get(Membership.INVITE, empty_ms).count
  )
 
- if name_id or canonical_alias_id:
- defer.returnValue(summary)
+ # if the room has a name or canonical_alias set, we can skip
+ # calculating heroes. we assume that if the event has contents, it'll
+ # be a valid name or canonical_alias - i.e. we're checking that they
+ # haven't been "deleted" by blatting {} over the top.
+ if name_id:
+ name = yield self.store.get_event(name_id, allow_none=False)
+ if name and name.content:
+ defer.returnValue(summary)
+
+ if canonical_alias_id:
+ canonical_alias = yield self.store.get_event(
+ canonical_alias_id, allow_none=False,
+ )
+ if canonical_alias and canonical_alias.content:
+ defer.returnValue(summary)
 
  joined_user_ids = [
  r[0] for r in details.get(Membership.JOIN, empty_ms).members