diff --git a/synapse/handlers/space_summary.py b/synapse/handlers/space_summary.py
index 2e997841f1..e35d91832b 100644
--- a/synapse/handlers/space_summary.py
+++ b/synapse/handlers/space_summary.py
@@ -14,6 +14,7 @@
import itertools
import logging
+import re
from collections import deque
from typing import TYPE_CHECKING, Iterable, List, Optional, Sequence, Set, Tuple, cast
@@ -226,6 +227,23 @@ class SpaceSummaryHandler:
suggested_only: bool,
max_children: Optional[int],
) -> Tuple[Sequence[JsonDict], Sequence[JsonDict]]:
+ """
+ Generate a room entry and a list of event entries for a given room.
+
+ Args:
+ requester: The requesting user, or None if this is over federation.
+ room_id: The room ID to summarize.
+ suggested_only: True if only suggested children should be returned.
+ Otherwise, all children are returned.
+ max_children: The maximum number of children to return for this node.
+
+ Returns:
+ A tuple of:
+ An iterable of a single value of the room.
+
+ An iterable of the sorted children events. This may be limited
+ to a maximum size or may include all children.
+ """
if not await self._is_room_accessible(room_id, requester):
return (), ()
@@ -357,6 +375,18 @@ class SpaceSummaryHandler:
return room_entry
async def _get_child_events(self, room_id: str) -> Iterable[EventBase]:
+ """
+ Get the child events for a given room.
+
+ The returned results are sorted for stability.
+
+ Args:
+ room_id: The room id to get the children of.
+
+ Returns:
+ An iterable of sorted child events.
+ """
+
# look for child rooms/spaces.
current_state_ids = await self._store.get_current_state_ids(room_id)
@@ -370,8 +400,9 @@ class SpaceSummaryHandler:
]
)
- # filter out any events without a "via" (which implies it has been redacted)
- return (e for e in events if _has_valid_via(e))
+ # filter out any events without a "via" (which implies it has been redacted),
+ # and order to ensure we return stable results.
+ return sorted(filter(_has_valid_via, events), key=_child_events_comparison_key)
@attr.s(frozen=True, slots=True)
@@ -397,3 +428,39 @@ def _is_suggested_child_event(edge_event: EventBase) -> bool:
return True
logger.debug("Ignorning not-suggested child %s", edge_event.state_key)
return False
+
+
+# Order may only contain characters in the range of \x20 (space) to \x7F (~).
+_INVALID_ORDER_CHARS_RE = re.compile(r"[^\x20-\x7F]")
+
+
+def _child_events_comparison_key(child: EventBase) -> Tuple[bool, Optional[str], str]:
+ """
+ Generate a value for comparing two child events for ordering.
+
+ The rules for ordering are supposed to be:
+
+ 1. The 'order' key, if it is valid.
+ 2. The 'origin_server_ts' of the 'm.room.create' event.
+ 3. The 'room_id'.
+
+ But we skip step 2 since we may not have any state from the room.
+
+ Args:
+ child: The event for generating a comparison key.
+
+ Returns:
+ The comparison key as a tuple of:
+ False if the ordering is valid.
+ The ordering field.
+ The room ID.
+ """
+ order = child.content.get("order")
+ # If order is not a string or doesn't meet the requirements, ignore it.
+ if not isinstance(order, str):
+ order = None
+ elif len(order) > 50 or _INVALID_ORDER_CHARS_RE.search(order):
+ order = None
+
+ # Items without an order come last.
+ return (order is None, order, child.room_id)
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