1 files changed, 29 insertions, 19 deletions

diff --git a/synapse/push/presentable_names.py b/synapse/push/presentable_names.py
index d8f4a453cd..7e50341d74 100644
--- a/synapse/push/presentable_names.py
+++ b/synapse/push/presentable_names.py
@@ -15,8 +15,14 @@
 
 import logging
 import re
+from typing import TYPE_CHECKING, Dict, Iterable, Optional
 
 from synapse.api.constants import EventTypes
+from synapse.events import EventBase
+from synapse.types import StateMap
+
+if TYPE_CHECKING:
+    from synapse.storage.databases.main import DataStore
 
 logger = logging.getLogger(__name__)
 
@@ -28,25 +34,29 @@ ALL_ALONE = "Empty Room"
 
 
 async def calculate_room_name(
-    store,
-    room_state_ids,
-    user_id,
-    fallback_to_members=True,
-    fallback_to_single_member=True,
-):
+    store: "DataStore",
+    room_state_ids: StateMap[str],
+    user_id: str,
+    fallback_to_members: bool = True,
+    fallback_to_single_member: bool = True,
+) -> Optional[str]:
     """
     Works out a user-facing name for the given room as per Matrix
     spec recommendations.
     Does not yet support internationalisation.
     Args:
-        room_state: Dictionary of the room's state
+        store: The data store to query.
+        room_state_ids: Dictionary of the room's state IDs.
         user_id: The ID of the user to whom the room name is being presented
         fallback_to_members: If False, return None instead of generating a name
                              based on the room's members if the room has no
                              title or aliases.
+        fallback_to_single_member: If False, return None instead of generating a
+            name based on the user who invited this user to the room if the room
+            has no title or aliases.
 
     Returns:
-        (string or None) A human readable name for the room.
+        A human readable name for the room, if possible.
     """
     # does it have a name?
     if (EventTypes.Name, "") in room_state_ids:
@@ -97,7 +107,7 @@ async def calculate_room_name(
                         name_from_member_event(inviter_member_event),
                     )
                 else:
-                    return
+                    return None
         else:
             return "Room Invite"
 
@@ -150,19 +160,19 @@ async def calculate_room_name(
         else:
             return ALL_ALONE
     elif len(other_members) == 1 and not fallback_to_single_member:
-        return
-    else:
-        return descriptor_from_member_events(other_members)
+        return None
+
+    return descriptor_from_member_events(other_members)
 
 
-def descriptor_from_member_events(member_events):
+def descriptor_from_member_events(member_events: Iterable[EventBase]) -> str:
     """Get a description of the room based on the member events.
 
     Args:
-        member_events (Iterable[FrozenEvent])
+        member_events: The events of a room.
 
     Returns:
-        str
+        The room description
     """
 
     member_events = list(member_events)
@@ -183,7 +193,7 @@ def descriptor_from_member_events(member_events):
         )
 
 
-def name_from_member_event(member_event):
+def name_from_member_event(member_event: EventBase) -> str:
     if (
         member_event.content
         and "displayname" in member_event.content
@@ -193,12 +203,12 @@ def name_from_member_event(member_event):
     return member_event.state_key
 
 
-def _state_as_two_level_dict(state):
-    ret = {}
+def _state_as_two_level_dict(state: StateMap[str]) -> Dict[str, Dict[str, str]]:
+    ret = {}  # type: Dict[str, Dict[str, str]]
     for k, v in state.items():
         ret.setdefault(k[0], {})[k[1]] = v
     return ret
 
 
-def _looks_like_an_alias(string):
+def _looks_like_an_alias(string: str) -> bool:
     return ALIAS_RE.match(string) is not None