Add helper to parse an enum from query args & use it. (#14956)

The `parse_enum` helper pulls an enum value from the query string
(by delegating down to the parse_string helper with values generated
from the enum).

This is used to pull out "f" and "b" in most places and then we thread
the resulting Direction enum throughout more code.

1 files changed, 9 insertions, 3 deletions

diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index c9a6dfd1a4..8d36172484 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -34,7 +34,13 @@ from prometheus_client import Counter, Gauge, Histogram
 from twisted.internet.abstract import isIPAddress
 from twisted.python import failure
 
-from synapse.api.constants import EduTypes, EventContentFields, EventTypes, Membership
+from synapse.api.constants import (
+    Direction,
+    EduTypes,
+    EventContentFields,
+    EventTypes,
+    Membership,
+)
 from synapse.api.errors import (
     AuthError,
     Codes,
@@ -218,7 +224,7 @@ class FederationServer(FederationBase):
         return 200, res
 
     async def on_timestamp_to_event_request(
-        self, origin: str, room_id: str, timestamp: int, direction: str
+        self, origin: str, room_id: str, timestamp: int, direction: Direction
     ) -> Tuple[int, Dict[str, Any]]:
         """When we receive a federated `/timestamp_to_event` request,
         handle all of the logic for validating and fetching the event.
@@ -228,7 +234,7 @@ class FederationServer(FederationBase):
             room_id: Room to fetch the event from
             timestamp: The point in time (inclusive) we should navigate from in
                 the given direction to find the closest event.
-            direction: ["f"|"b"] to indicate whether we should navigate forward
+            direction: indicates whether we should navigate forward
                 or backward from the given timestamp to find the closest event.
 
         Returns: