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, 10 insertions, 5 deletions

diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index feb32e40e5..8493ffc2e5 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -37,7 +37,7 @@ from typing import (
 import attr
 from prometheus_client import Counter
 
-from synapse.api.constants import EventContentFields, EventTypes, Membership
+from synapse.api.constants import Direction, EventContentFields, EventTypes, Membership
 from synapse.api.errors import (
     CodeMessageException,
     Codes,
@@ -1680,7 +1680,12 @@ class FederationClient(FederationBase):
         return result
 
     async def timestamp_to_event(
-        self, *, destinations: List[str], room_id: str, timestamp: int, direction: str
+        self,
+        *,
+        destinations: List[str],
+        room_id: str,
+        timestamp: int,
+        direction: Direction,
     ) -> Optional["TimestampToEventResponse"]:
         """
         Calls each remote federating server from `destinations` asking for their closest
@@ -1693,7 +1698,7 @@ class FederationClient(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:
@@ -1738,7 +1743,7 @@ class FederationClient(FederationBase):
             return None
 
     async def _timestamp_to_event_from_destination(
-        self, destination: str, room_id: str, timestamp: int, direction: str
+        self, destination: str, room_id: str, timestamp: int, direction: Direction
     ) -> "TimestampToEventResponse":
         """
         Calls a remote federating server at `destination` asking for their
@@ -1751,7 +1756,7 @@ class FederationClient(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: