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, 4 insertions, 3 deletions

diff --git a/synapse/rest/admin/federation.py b/synapse/rest/admin/federation.py
index 023ed92144..e0ee55bd0e 100644
--- a/synapse/rest/admin/federation.py
+++ b/synapse/rest/admin/federation.py
@@ -15,9 +15,10 @@ import logging
 from http import HTTPStatus
 from typing import TYPE_CHECKING, Tuple
 
+from synapse.api.constants import Direction
 from synapse.api.errors import Codes, NotFoundError, SynapseError
 from synapse.federation.transport.server import Authenticator
-from synapse.http.servlet import RestServlet, parse_integer, parse_string
+from synapse.http.servlet import RestServlet, parse_enum, parse_integer, parse_string
 from synapse.http.site import SynapseRequest
 from synapse.rest.admin._base import admin_patterns, assert_requester_is_admin
 from synapse.storage.databases.main.transactions import DestinationSortOrder
@@ -79,7 +80,7 @@ class ListDestinationsRestServlet(RestServlet):
             allowed_values=[dest.value for dest in DestinationSortOrder],
         )
 
-        direction = parse_string(request, "dir", default="f", allowed_values=("f", "b"))
+        direction = parse_enum(request, "dir", Direction, default=Direction.FORWARDS)
 
         destinations, total = await self._store.get_destinations_paginate(
             start, limit, destination, order_by, direction
@@ -192,7 +193,7 @@ class DestinationMembershipRestServlet(RestServlet):
                 errcode=Codes.INVALID_PARAM,
             )
 
-        direction = parse_string(request, "dir", default="f", allowed_values=("f", "b"))
+        direction = parse_enum(request, "dir", Direction, default=Direction.FORWARDS)
 
         rooms, total = await self._store.get_destination_rooms_paginate(
             destination, start, limit, direction