Use an enum for direction. (#14927)

For better type safety we  use an enum instead of strings to
configure direction (backwards or forwards).

4 files changed, 25 insertions, 9 deletions

diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index 5bf8e86387..c81ea34758 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -16,7 +16,7 @@ import abc
 import logging
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Set
 
-from synapse.api.constants import Membership
+from synapse.api.constants import Direction, Membership
 from synapse.events import EventBase
 from synapse.types import JsonDict, RoomStreamToken, StateMap, UserID
 from synapse.visibility import filter_events_for_client
@@ -197,7 +197,7 @@ class AdminHandler:
             # efficient method perhaps but it does guarantee we get everything.
             while True:
                 events, _ = await self.store.paginate_room_events(
-                    room_id, from_key, to_key, limit=100, direction="f"
+                    room_id, from_key, to_key, limit=100, direction=Direction.FORWARDS
                 )
                 if not events:
                     break
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 8c2260ad7d..191529bd8e 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -15,7 +15,13 @@
 import logging
 from typing import TYPE_CHECKING, List, Optional, Tuple, cast
 
-from synapse.api.constants import AccountDataTypes, EduTypes, EventTypes, Membership
+from synapse.api.constants import (
+    AccountDataTypes,
+    Direction,
+    EduTypes,
+    EventTypes,
+    Membership,
+)
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase
 from synapse.events.utils import SerializeEventConfig
@@ -57,7 +63,13 @@ class InitialSyncHandler:
         self.validator = EventValidator()
         self.snapshot_cache: ResponseCache[
             Tuple[
-                str, Optional[StreamToken], Optional[StreamToken], str, int, bool, bool
+                str,
+                Optional[StreamToken],
+                Optional[StreamToken],
+                Direction,
+                int,
+                bool,
+                bool,
             ]
         ] = ResponseCache(hs.get_clock(), "initial_sync_cache")
         self._event_serializer = hs.get_event_client_serializer()
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 1fe6567185..ceefa16b49 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -19,7 +19,7 @@ import attr
 
 from twisted.python.failure import Failure
 
-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import Direction, EventTypes, Membership
 from synapse.api.errors import SynapseError
 from synapse.api.filtering import Filter
 from synapse.events.utils import SerializeEventConfig
@@ -448,7 +448,7 @@ class PaginationHandler:
 
         if pagin_config.from_token:
             from_token = pagin_config.from_token
-        elif pagin_config.direction == "f":
+        elif pagin_config.direction == Direction.FORWARDS:
             from_token = (
                 await self.hs.get_event_sources().get_start_token_for_pagination(
                     room_id
@@ -476,7 +476,7 @@ class PaginationHandler:
                     room_id, requester, allow_departed_users=True
                 )
 
-            if pagin_config.direction == "b":
+            if pagin_config.direction == Direction.BACKWARDS:
                 # if we're going backwards, we might need to backfill. This
                 # requires that we have a topo token.
                 if room_token.topological:
diff --git a/synapse/handlers/relations.py b/synapse/handlers/relations.py
index e96f9999a8..0fb15391e0 100644
--- a/synapse/handlers/relations.py
+++ b/synapse/handlers/relations.py
@@ -17,7 +17,7 @@ from typing import TYPE_CHECKING, Collection, Dict, FrozenSet, Iterable, List, O
 
 import attr
 
-from synapse.api.constants import EventTypes, RelationTypes
+from synapse.api.constants import Direction, EventTypes, RelationTypes
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase, relation_from_event
 from synapse.logging.context import make_deferred_yieldable, run_in_background
@@ -413,7 +413,11 @@ class RelationsHandler:
 
                 # Attempt to find another event to use as the latest event.
                 potential_events, _ = await self._main_store.get_relations_for_event(
-                    event_id, event, room_id, RelationTypes.THREAD, direction="f"
+                    event_id,
+                    event,
+                    room_id,
+                    RelationTypes.THREAD,
+                    direction=Direction.FORWARDS,
                 )
 
                 # Filter out ignored users.