Flatten _get_new_state_after_events

rejig the if statements to simplify the logic and reduce indentation

synapse/storage/events.py

@@ -503,6 +503,10 @@ class EventsStore(SQLBaseStore):
                 None if there are no changes to the room state, or
                 a dict of (type, state_key) -> event_id].
         """
+
+        if not new_latest_event_ids:
+            defer.returnValue({})
+
         state_sets = []
         state_groups = set()
         missing_event_ids = []
@@ -537,6 +541,9 @@ class EventsStore(SQLBaseStore):
                 was_updated = True
                 missing_event_ids.append(event_id)
 
+        if not was_updated:
+            return
+
         if missing_event_ids:
             # Now pull out the state for any missing events from DB
             event_to_groups = yield self._get_state_group_for_events(
@@ -549,14 +556,11 @@ class EventsStore(SQLBaseStore):
                 group_to_state = yield self._get_state_for_groups(groups)
                 state_sets.extend(group_to_state.itervalues())
 
-        if not new_latest_event_ids:
-            defer.returnValue({})
-        elif was_updated:
         if len(state_sets) == 1:
             # If there is only one state set, then we know what the current
             # state is.
             defer.returnValue(state_sets[0])
-            else:
+
         # We work out the current state by passing the state sets to the
         # state resolution algorithm. It may ask for some events, including
         # the events we have yet to persist, so we need a slightly more
@@ -595,8 +599,6 @@ class EventsStore(SQLBaseStore):
             state_map_factory=get_events,
         )
         defer.returnValue(current_state)
-        else:
-            return
 
     @defer.inlineCallbacks
     def _calculate_state_delta(self, room_id, current_state):