Clarify list/set/dict/tuple comprehensions and enforce via flake8

CONTRIBUTING.md

@@ -60,7 +60,7 @@ python 3.6 and to install each tool:
 
 ```
 # Install the dependencies
-pip install -U black flake8 isort
+pip install -U black flake8 flake8-comprehensions isort
 
 # Run the linter script
 ./scripts-dev/lint.sh

changelog.d/6957.misc

@@ -0,0 +1 @@
+Use flake8-comprehensions to enforce good hygiene of list/set/dict comprehensions.

docs/code_style.md

@@ -30,7 +30,7 @@ The necessary tools are detailed below.
 
     Install `flake8` with:
 
-        pip install --upgrade flake8
+        pip install --upgrade flake8 flake8-comprehensions
 
     Check all application and test code with:
 

scripts-dev/convert_server_keys.py

@@ -103,7 +103,7 @@ def main():
 
     yaml.safe_dump(result, sys.stdout, default_flow_style=False)
 
-    rows = list(row for server, json in result.items() for row in rows_v2(server, json))
+    rows = [row for server, json in result.items() for row in rows_v2(server, json)]
 
     cursor = connection.cursor()
     cursor.executemany(

synapse/app/_base.py

@@ -141,7 +141,7 @@ def run():
 
 def quit_with_error(error_string):
     message_lines = error_string.split("\n")
-    line_length = max([len(l) for l in message_lines if len(l) < 80]) + 2
+    line_length = max(len(l) for l in message_lines if len(l) < 80) + 2
     sys.stderr.write("*" * line_length + "\n")
     for line in message_lines:
         sys.stderr.write(" %s\n" % (line.rstrip(),))

synapse/app/federation_sender.py

@@ -262,15 +262,15 @@ def process_replication_rows(self, stream_name, token, rows):
 
         # ... as well as device updates and messages
         elif stream_name == DeviceListsStream.NAME:
-            hosts = set(row.destination for row in rows)
+            hosts = {row.destination for row in rows}
             for host in hosts:
                 self.federation_sender.send_device_messages(host)
 
         elif stream_name == ToDeviceStream.NAME:
             # The to_device stream includes stuff to be pushed to both local
             # clients and remote servers, so we ignore entities that start with
             # '@' (since they'll be local users rather than destinations).
-            hosts = set(row.entity for row in rows if not row.entity.startswith("@"))
+            hosts = {row.entity for row in rows if not row.entity.startswith("@")}
             for host in hosts:
                 self.federation_sender.send_device_messages(host)
 

synapse/app/pusher.py

@@ -158,7 +158,7 @@ def poke_pushers(self, stream_name, token, rows):
                 yield self.pusher_pool.on_new_notifications(token, token)
             elif stream_name == "receipts":
                 yield self.pusher_pool.on_new_receipts(
-                    token, token, set(row.room_id for row in rows)
+                    token, token, {row.room_id for row in rows}
                 )
         except Exception:
             logger.exception("Error poking pushers")

synapse/config/server.py

@@ -1066,12 +1066,12 @@ def _warn_if_webclient_configured(listeners):
 
 
 def _check_resource_config(listeners):
-    resource_names = set(
+    resource_names = {
         res_name
         for listener in listeners
         for res in listener.get("resources", [])
         for res_name in res.get("names", [])
-    )
+    }
 
     for resource in resource_names:
         if resource not in KNOWN_RESOURCES:

synapse/config/tls.py

@@ -260,7 +260,7 @@ def read_certificate_from_disk(self, require_cert_and_key):
                 crypto.FILETYPE_ASN1, self.tls_certificate
             )
             sha256_fingerprint = encode_base64(sha256(x509_certificate_bytes).digest())
-            sha256_fingerprints = set(f["sha256"] for f in self.tls_fingerprints)
+            sha256_fingerprints = {f["sha256"] for f in self.tls_fingerprints}
             if sha256_fingerprint not in sha256_fingerprints:
                 self.tls_fingerprints.append({"sha256": sha256_fingerprint})
 

synapse/crypto/keyring.py

@@ -326,9 +326,7 @@ def _get_server_verify_keys(self, verify_requests):
             verify_requests (list[VerifyJsonRequest]): list of verify requests
         """
 
-        remaining_requests = set(
-            (rq for rq in verify_requests if not rq.key_ready.called)
-        )
+        remaining_requests = {rq for rq in verify_requests if not rq.key_ready.called}
 
         @defer.inlineCallbacks
         def do_iterations():
@@ -396,7 +394,7 @@ def _attempt_key_fetches_with_fetcher(self, fetcher, remaining_requests):
 
         results = yield fetcher.get_keys(missing_keys)
 
-        completed = list()
+        completed = []
         for verify_request in remaining_requests:
             server_name = verify_request.server_name
 

synapse/federation/send_queue.py

@@ -129,9 +129,9 @@ def _clear_queue_before_pos(self, position_to_delete):
             for key in keys[:i]:
                 del self.presence_changed[key]
 
-            user_ids = set(
+            user_ids = {
                 user_id for uids in self.presence_changed.values() for user_id in uids
-            )
+            }
 
             keys = self.presence_destinations.keys()
             i = self.presence_destinations.bisect_left(position_to_delete)

synapse/groups/groups_server.py

@@ -608,7 +608,7 @@ def invite_to_group(self, group_id, user_id, requester_user_id, content):
         user_results = yield self.store.get_users_in_group(
             group_id, include_private=True
         )
-        if user_id in [user_result["user_id"] for user_result in user_results]:
+        if user_id in (user_result["user_id"] for user_result in user_results):
             raise SynapseError(400, "User already in group")
 
         content = {

synapse/handlers/device.py

@@ -742,6 +742,6 @@ def user_device_resync(self, user_id):
 
         # We clobber the seen updates since we've re-synced from a given
         # point.
-        self._seen_updates[user_id] = set([stream_id])
+        self._seen_updates[user_id] = {stream_id}
 
         defer.returnValue(result)

synapse/handlers/directory.py

@@ -71,7 +71,7 @@ def _create_association(self, room_alias, room_id, servers=None, creator=None):
         # TODO(erikj): Check if there is a current association.
         if not servers:
             users = yield self.state.get_current_users_in_room(room_id)
-            servers = set(get_domain_from_id(u) for u in users)
+            servers = {get_domain_from_id(u) for u in users}
 
         if not servers:
             raise SynapseError(400, "Failed to get server list")
@@ -254,7 +254,7 @@ def get_association(self, room_alias):
             )
 
         users = yield self.state.get_current_users_in_room(room_id)
-        extra_servers = set(get_domain_from_id(u) for u in users)
+        extra_servers = {get_domain_from_id(u) for u in users}
         servers = set(extra_servers) | set(servers)
 
         # If this server is in the list of servers, return it first.

synapse/handlers/federation.py

@@ -659,11 +659,11 @@ async def _get_events_from_store_or_dest(
         # this can happen if a remote server claims that the state or
         # auth_events at an event in room A are actually events in room B
 
-        bad_events = list(
+        bad_events = [
             (event_id, event.room_id)
             for event_id, event in fetched_events.items()
             if event.room_id != room_id
-        )
+        ]
 
         for bad_event_id, bad_room_id in bad_events:
             # This is a bogus situation, but since we may only discover it a long time
@@ -856,7 +856,7 @@ async def backfill(self, dest, room_id, limit, extremities):
 
         # Don't bother processing events we already have.
         seen_events = await self.store.have_events_in_timeline(
-            set(e.event_id for e in events)
+            {e.event_id for e in events}
         )
 
         events = [e for e in events if e.event_id not in seen_events]
@@ -866,7 +866,7 @@ async def backfill(self, dest, room_id, limit, extremities):
 
         event_map = {e.event_id: e for e in events}
 
-        event_ids = set(e.event_id for e in events)
+        event_ids = {e.event_id for e in events}
 
         # build a list of events whose prev_events weren't in the batch.
         # (XXX: this will include events whose prev_events we already have; that doesn't
@@ -892,13 +892,13 @@ async def backfill(self, dest, room_id, limit, extremities):
             state_events.update({s.event_id: s for s in state})
             events_to_state[e_id] = state
 
-        required_auth = set(
+        required_auth = {
             a_id
             for event in events
             + list(state_events.values())
             + list(auth_events.values())
             for a_id in event.auth_event_ids()
-        )
+        }
         auth_events.update(
             {e_id: event_map[e_id] for e_id in required_auth if e_id in event_map}
         )
@@ -1247,7 +1247,7 @@ async def send_invite(self, target_host, event):
     async def on_event_auth(self, event_id: str) -> List[EventBase]:
         event = await self.store.get_event(event_id)
         auth = await self.store.get_auth_chain(
-            [auth_id for auth_id in event.auth_event_ids()], include_given=True
+            list(event.auth_event_ids()), include_given=True
         )
         return list(auth)
 
@@ -2152,7 +2152,7 @@ async def on_query_auth(
 
         # Now get the current auth_chain for the event.
         local_auth_chain = await self.store.get_auth_chain(
-            [auth_id for auth_id in event.auth_event_ids()], include_given=True
+            list(event.auth_event_ids()), include_given=True
         )
 
         # TODO: Check if we would now reject event_id. If so we need to tell
@@ -2654,7 +2654,7 @@ def exchange_third_party_invite(
             member_handler = self.hs.get_room_member_handler()
             yield member_handler.send_membership_event(None, event, context)
         else:
-            destinations = set(x.split(":", 1)[-1] for x in (sender_user_id, room_id))
+            destinations = {x.split(":", 1)[-1] for x in (sender_user_id, room_id)}
             yield self.federation_client.forward_third_party_invite(
                 destinations, room_id, event_dict
             )

synapse/handlers/presence.py

@@ -313,7 +313,7 @@ def _update_states(self, new_states):
                 notified_presence_counter.inc(len(to_notify))
                 yield self._persist_and_notify(list(to_notify.values()))
 
-            self.unpersisted_users_changes |= set(s.user_id for s in new_states)
+            self.unpersisted_users_changes |= {s.user_id for s in new_states}
             self.unpersisted_users_changes -= set(to_notify.keys())
 
             to_federation_ping = {
@@ -698,7 +698,7 @@ def get_states(self, target_user_ids, as_event=False):
         updates = yield self.current_state_for_users(target_user_ids)
         updates = list(updates.values())
 
-        for user_id in set(target_user_ids) - set(u.user_id for u in updates):
+        for user_id in set(target_user_ids) - {u.user_id for u in updates}:
             updates.append(UserPresenceState.default(user_id))
 
         now = self.clock.time_msec()
@@ -886,7 +886,7 @@ def _on_user_joined_room(self, room_id, user_id):
             hosts = yield self.state.get_current_hosts_in_room(room_id)
 
             # Filter out ourselves.
-            hosts = set(host for host in hosts if host != self.server_name)
+            hosts = {host for host in hosts if host != self.server_name}
 
             self.federation.send_presence_to_destinations(
                 states=[state], destinations=hosts

synapse/handlers/receipts.py

@@ -94,7 +94,7 @@ async def _handle_new_receipts(self, receipts):
             # no new receipts
             return False
 
-        affected_room_ids = list(set([r.room_id for r in receipts]))
+        affected_room_ids = list({r.room_id for r in receipts})
 
         self.notifier.on_new_event("receipt_key", max_batch_id, rooms=affected_room_ids)
         # Note that the min here shouldn't be relied upon to be accurate.

synapse/handlers/room.py

@@ -353,7 +353,7 @@ def clone_existing_room(
             # If so, mark the new room as non-federatable as well
             creation_content["m.federate"] = False
 
-        initial_state = dict()
+        initial_state = {}
 
         # Replicate relevant room events
         types_to_copy = (

synapse/handlers/search.py

@@ -184,7 +184,7 @@ def search(self, user, content, batch=None):
             membership_list=[Membership.JOIN],
             # membership_list=[Membership.JOIN, Membership.LEAVE, Membership.Ban],
         )
-        room_ids = set(r.room_id for r in rooms)
+        room_ids = {r.room_id for r in rooms}
 
         # If doing a subset of all rooms seearch, check if any of the rooms
         # are from an upgraded room, and search their contents as well
@@ -374,12 +374,12 @@ def search(self, user, content, batch=None):
                 ).to_string()
 
                 if include_profile:
-                    senders = set(
+                    senders = {
                         ev.sender
                         for ev in itertools.chain(
                             res["events_before"], [event], res["events_after"]
                         )
-                    )
+                    }
 
                     if res["events_after"]:
                         last_event_id = res["events_after"][-1].event_id
@@ -421,7 +421,7 @@ def search(self, user, content, batch=None):
 
         state_results = {}
         if include_state:
-            rooms = set(e.room_id for e in allowed_events)
+            rooms = {e.room_id for e in allowed_events}
             for room_id in rooms:
                 state = yield self.state_handler.get_current_state(room_id)
                 state_results[room_id] = list(state.values())

synapse/handlers/sync.py

@@ -682,11 +682,9 @@ async def compute_summary(
 
         # FIXME: order by stream ordering rather than as returned by SQL
         if joined_user_ids or invited_user_ids:
-            summary["m.heroes"] = sorted(
-                [user_id for user_id in (joined_user_ids + invited_user_ids)]
-            )[0:5]
+            summary["m.heroes"] = sorted(joined_user_ids + invited_user_ids)[0:5]
         else:
-            summary["m.heroes"] = sorted([user_id for user_id in gone_user_ids])[0:5]
+            summary["m.heroes"] = sorted(gone_user_ids)[0:5]
 
         if not sync_config.filter_collection.lazy_load_members():
             return summary
@@ -697,9 +695,9 @@ async def compute_summary(
 
         # track which members the client should already know about via LL:
         # Ones which are already in state...
-        existing_members = set(
+        existing_members = {
             user_id for (typ, user_id) in state.keys() if typ == EventTypes.Member
-        )
+        }
 
         # ...or ones which are in the timeline...
         for ev in batch.events:
@@ -773,10 +771,10 @@ async def compute_state_delta(
                 # We only request state for the members needed to display the
                 # timeline:
 
-                members_to_fetch = set(
+                members_to_fetch = {
                     event.sender  # FIXME: we also care about invite targets etc.
                     for event in batch.events
-                )
+                }
 
                 if full_state:
                     # always make sure we LL ourselves so we know we're in the room
@@ -1993,10 +1991,10 @@ def _calculate_state(
         )
     }
 
-    c_ids = set(e for e in itervalues(current))
-    ts_ids = set(e for e in itervalues(timeline_start))
-    p_ids = set(e for e in itervalues(previous))
-    tc_ids = set(e for e in itervalues(timeline_contains))
+    c_ids = set(itervalues(current))
+    ts_ids = set(itervalues(timeline_start))
+    p_ids = set(itervalues(previous))
+    tc_ids = set(itervalues(timeline_contains))
 
     # If we are lazyloading room members, we explicitly add the membership events
     # for the senders in the timeline into the state block returned by /sync,

synapse/handlers/typing.py

@@ -198,7 +198,7 @@ def _push_remote(self, member, typing):
                 now=now, obj=member, then=now + FEDERATION_PING_INTERVAL
             )
 
-            for domain in set(get_domain_from_id(u) for u in users):
+            for domain in {get_domain_from_id(u) for u in users}:
                 if domain != self.server_name:
                     logger.debug("sending typing update to %s", domain)
                     self.federation.build_and_send_edu(
@@ -231,7 +231,7 @@ def _recv_edu(self, origin, content):
             return
 
         users = yield self.state.get_current_users_in_room(room_id)
-        domains = set(get_domain_from_id(u) for u in users)
+        domains = {get_domain_from_id(u) for u in users}
 
         if self.server_name in domains:
             logger.info("Got typing update from %s: %r", user_id, content)

synapse/logging/utils.py

@@ -148,7 +148,7 @@ def wrapped(*args, **kwargs):
             pathname=pathname,
             lineno=lineno,
             msg=msg,
-            args=tuple(),
+            args=(),
             exc_info=None,
         )
 

synapse/metrics/__init__.py

@@ -240,7 +240,7 @@ def collect(self):
         res.append(["+Inf", sum(data.values())])
 
         metric = HistogramMetricFamily(
-            self.name, "", buckets=res, sum_value=sum([x * y for x, y in data.items()])
+            self.name, "", buckets=res, sum_value=sum(x * y for x, y in data.items())
         )
         yield metric