Fix incorrect thread summaries when the latest event is edited. (#11992)

If the latest event in a thread was edited than the original
event content was included in bundled aggregation for
threads instead of the edited event content.

1 files changed, 18 insertions, 6 deletions

diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index e2c27e594b..5582029f9f 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -53,8 +53,13 @@ logger = logging.getLogger(__name__)
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
 class _ThreadAggregation:
+    # The latest event in the thread.
     latest_event: EventBase
+    # The latest edit to the latest event in the thread.
+    latest_edit: Optional[EventBase]
+    # The total number of events in the thread.
     count: int
+    # True if the current user has sent an event to the thread.
     current_user_participated: bool
 
 
@@ -461,8 +466,8 @@ class RelationsWorkerStore(SQLBaseStore):
     @cachedList(cached_method_name="get_thread_summary", list_name="event_ids")
     async def _get_thread_summaries(
         self, event_ids: Collection[str]
-    ) -> Dict[str, Optional[Tuple[int, EventBase]]]:
-        """Get the number of threaded replies and the latest reply (if any) for the given event.
+    ) -> Dict[str, Optional[Tuple[int, EventBase, Optional[EventBase]]]]:
+        """Get the number of threaded replies, the latest reply (if any), and the latest edit for that reply for the given event.
 
         Args:
             event_ids: Summarize the thread related to this event ID.
@@ -471,8 +476,10 @@ class RelationsWorkerStore(SQLBaseStore):
             A map of the thread summary each event. A missing event implies there
             are no threaded replies.
 
-            Each summary includes the number of items in the thread and the most
-            recent response.
+            Each summary is a tuple of:
+                The number of events in the thread.
+                The most recent event in the thread.
+                The most recent edit to the most recent event in the thread, if applicable.
         """
 
         def _get_thread_summaries_txn(
@@ -558,6 +565,9 @@ class RelationsWorkerStore(SQLBaseStore):
 
         latest_events = await self.get_events(latest_event_ids.values())  # type: ignore[attr-defined]
 
+        # Check to see if any of those events are edited.
+        latest_edits = await self._get_applicable_edits(latest_event_ids.values())
+
         # Map to the event IDs to the thread summary.
         #
         # There might not be a summary due to there not being a thread or
@@ -568,7 +578,8 @@ class RelationsWorkerStore(SQLBaseStore):
 
             summary = None
             if latest_event:
-                summary = (counts[parent_event_id], latest_event)
+                latest_edit = latest_edits.get(latest_event_id)
+                summary = (counts[parent_event_id], latest_event, latest_edit)
             summaries[parent_event_id] = summary
 
         return summaries
@@ -828,11 +839,12 @@ class RelationsWorkerStore(SQLBaseStore):
             )
             for event_id, summary in summaries.items():
                 if summary:
-                    thread_count, latest_thread_event = summary
+                    thread_count, latest_thread_event, edit = summary
                     results.setdefault(
                         event_id, BundledAggregations()
                     ).thread = _ThreadAggregation(
                         latest_event=latest_thread_event,
+                        latest_edit=edit,
                         count=thread_count,
                         # If there's a thread summary it must also exist in the
                         # participated dictionary.