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, 2 insertions, 1 deletions

diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index 9dd59196d9..7456d6f507 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -16,6 +16,7 @@ import logging
 import re
 from typing import TYPE_CHECKING, Optional, Tuple
 
+from synapse.api.constants import Direction
 from synapse.handlers.relations import ThreadsListInclude
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_integer, parse_string
@@ -59,7 +60,7 @@ class RelationPaginationServlet(RestServlet):
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         pagination_config = await PaginationConfig.from_request(
-            self._store, request, default_limit=5, default_dir="b"
+            self._store, request, default_limit=5, default_dir=Direction.BACKWARDS
         )
 
         # The unstable version of this API returns an extra field for client