Clarify list/set/dict/tuple comprehensions and enforce via flake8 (#6957)

Ensure good comprehension hygiene using flake8-comprehensions.

4 files changed, 14 insertions, 18 deletions

diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 7d9f5a38d9..433ca2f416 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -400,11 +400,11 @@ class RulesForRoom(object):
         if logger.isEnabledFor(logging.DEBUG):
             logger.debug("Found members %r: %r", self.room_id, members.values())
 
-        interested_in_user_ids = set(
+        interested_in_user_ids = {
             user_id
             for user_id, membership in itervalues(members)
             if membership == Membership.JOIN
-        )
+        }
 
         logger.debug("Joined: %r", interested_in_user_ids)
 
@@ -412,9 +412,9 @@ class RulesForRoom(object):
             interested_in_user_ids, on_invalidate=self.invalidate_all_cb
         )
 
-        user_ids = set(
+        user_ids = {
             uid for uid, have_pusher in iteritems(if_users_with_pushers) if have_pusher
-        )
+        }
 
         logger.debug("With pushers: %r", user_ids)
 
diff --git a/synapse/push/emailpusher.py b/synapse/push/emailpusher.py
index 8c818a86bf..ba4551d619 100644
--- a/synapse/push/emailpusher.py
+++ b/synapse/push/emailpusher.py
@@ -204,7 +204,7 @@ class EmailPusher(object):
                 yield self.send_notification(unprocessed, reason)
 
                 yield self.save_last_stream_ordering_and_success(
-                    max([ea["stream_ordering"] for ea in unprocessed])
+                    max(ea["stream_ordering"] for ea in unprocessed)
                 )
 
                 # we update the throttle on all the possible unprocessed push actions
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index b13b646bfd..4ccaf178ce 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -526,12 +526,10 @@ class Mailer(object):
                     # If the room doesn't have a name, say who the messages
                     # are from explicitly to avoid, "messages in the Bob room"
                     sender_ids = list(
-                        set(
-                            [
-                                notif_events[n["event_id"]].sender
-                                for n in notifs_by_room[room_id]
-                            ]
-                        )
+                        {
+                            notif_events[n["event_id"]].sender
+                            for n in notifs_by_room[room_id]
+                        }
                     )
 
                     member_events = yield self.store.get_events(
@@ -558,12 +556,10 @@ class Mailer(object):
                 # If the reason room doesn't have a name, say who the messages
                 # are from explicitly to avoid, "messages in the Bob room"
                 sender_ids = list(
-                    set(
-                        [
-                            notif_events[n["event_id"]].sender
-                            for n in notifs_by_room[reason["room_id"]]
-                        ]
-                    )
+                    {
+                        notif_events[n["event_id"]].sender
+                        for n in notifs_by_room[reason["room_id"]]
+                    }
                 )
 
                 member_events = yield self.store.get_events(
diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py
index b9dca5bc63..01789a9fb4 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -191,7 +191,7 @@ class PusherPool:
                 min_stream_id - 1, max_stream_id
             )
             # This returns a tuple, user_id is at index 3
-            users_affected = set([r[3] for r in updated_receipts])
+            users_affected = {r[3] for r in updated_receipts}
 
             for u in users_affected:
                 if u in self.pushers: