Do not consider events by ignored users for bundled aggregations (#12235)

Consider the requester's ignored users when calculating the
bundled aggregations.

See #12285 / 4df10d32148ae29f792afc68ff774bcbd1915cea
for corresponding changes for the `/relations` endpoint.

6 files changed, 427 insertions, 45 deletions

diff --git a/changelog.d/12235.bugfix b/changelog.d/12235.bugfix
new file mode 100644
index 0000000000..b5d2bede67
--- /dev/null
+++ b/changelog.d/12235.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where events from ignored users were still considered for bundled aggregations.
diff --git a/changelog.d/12338.bugfix b/changelog.d/12338.bugfix
new file mode 100644
index 0000000000..b5d2bede67
--- /dev/null
+++ b/changelog.d/12338.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where events from ignored users were still considered for bundled aggregations.
diff --git a/changelog.d/12338.misc b/changelog.d/12338.misc
deleted file mode 100644
index 376089f327..0000000000
--- a/changelog.d/12338.misc
+++ /dev/null
@@ -1 +0,0 @@
-Refactor relations code to remove an unnecessary class.
diff --git a/synapse/handlers/relations.py b/synapse/handlers/relations.py
index a36936b520..0be2319577 100644
--- a/synapse/handlers/relations.py
+++ b/synapse/handlers/relations.py
@@ -12,7 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Dict, Iterable, Optional
+from typing import (
+    TYPE_CHECKING,
+    Collection,
+    Dict,
+    FrozenSet,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+)
 
 import attr
 from frozendict import frozendict
@@ -20,7 +29,8 @@ from frozendict import frozendict
 from synapse.api.constants import RelationTypes
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase
-from synapse.types import JsonDict, Requester, StreamToken
+from synapse.storage.databases.main.relations import _RelatedEvent
+from synapse.types import JsonDict, Requester, StreamToken, UserID
 from synapse.visibility import filter_events_for_client
 
 if TYPE_CHECKING:
@@ -115,6 +125,9 @@ class RelationsHandler:
         if event is None:
             raise SynapseError(404, "Unknown parent event.")
 
+        # Note that ignored users are not passed into get_relations_for_event
+        # below. Ignored users are handled in filter_events_for_client (and by
+        # not passing them in here we should get a better cache hit rate).
         related_events, next_token = await self._main_store.get_relations_for_event(
             event_id=event_id,
             event=event,
@@ -128,7 +141,9 @@ class RelationsHandler:
             to_token=to_token,
         )
 
-        events = await self._main_store.get_events_as_list(related_events)
+        events = await self._main_store.get_events_as_list(
+            [e.event_id for e in related_events]
+        )
 
         events = await filter_events_for_client(
             self._storage, user_id, events, is_peeking=(member_event_id is None)
@@ -162,8 +177,87 @@ class RelationsHandler:
 
         return return_value
 
+    async def get_relations_for_event(
+        self,
+        event_id: str,
+        event: EventBase,
+        room_id: str,
+        relation_type: str,
+        ignored_users: FrozenSet[str] = frozenset(),
+    ) -> Tuple[List[_RelatedEvent], Optional[StreamToken]]:
+        """Get a list of events which relate to an event, ordered by topological ordering.
+
+        Args:
+            event_id: Fetch events that relate to this event ID.
+            event: The matching EventBase to event_id.
+            room_id: The room the event belongs to.
+            relation_type: The type of relation.
+            ignored_users: The users ignored by the requesting user.
+
+        Returns:
+            List of event IDs that match relations requested. The rows are of
+            the form `{"event_id": "..."}`.
+        """
+
+        # Call the underlying storage method, which is cached.
+        related_events, next_token = await self._main_store.get_relations_for_event(
+            event_id, event, room_id, relation_type, direction="f"
+        )
+
+        # Filter out ignored users and convert to the expected format.
+        related_events = [
+            event for event in related_events if event.sender not in ignored_users
+        ]
+
+        return related_events, next_token
+
+    async def get_annotations_for_event(
+        self,
+        event_id: str,
+        room_id: str,
+        limit: int = 5,
+        ignored_users: FrozenSet[str] = frozenset(),
+    ) -> List[JsonDict]:
+        """Get a list of annotations on the event, grouped by event type and
+        aggregation key, sorted by count.
+
+        This is used e.g. to get the what and how many reactions have happend
+        on an event.
+
+        Args:
+            event_id: Fetch events that relate to this event ID.
+            room_id: The room the event belongs to.
+            limit: Only fetch the `limit` groups.
+            ignored_users: The users ignored by the requesting user.
+
+        Returns:
+            List of groups of annotations that match. Each row is a dict with
+            `type`, `key` and `count` fields.
+        """
+        # Get the base results for all users.
+        full_results = await self._main_store.get_aggregation_groups_for_event(
+            event_id, room_id, limit
+        )
+
+        # Then subtract off the results for any ignored users.
+        ignored_results = await self._main_store.get_aggregation_groups_for_users(
+            event_id, room_id, limit, ignored_users
+        )
+
+        filtered_results = []
+        for result in full_results:
+            key = (result["type"], result["key"])
+            if key in ignored_results:
+                result = result.copy()
+                result["count"] -= ignored_results[key]
+                if result["count"] <= 0:
+                    continue
+            filtered_results.append(result)
+
+        return filtered_results
+
     async def _get_bundled_aggregation_for_event(
-        self, event: EventBase, user_id: str
+        self, event: EventBase, ignored_users: FrozenSet[str]
     ) -> Optional[BundledAggregations]:
         """Generate bundled aggregations for an event.
 
@@ -171,7 +265,7 @@ class RelationsHandler:
 
         Args:
             event: The event to calculate bundled aggregations for.
-            user_id: The user requesting the bundled aggregations.
+            ignored_users: The users ignored by the requesting user.
 
         Returns:
             The bundled aggregations for an event, if bundled aggregations are
@@ -194,18 +288,22 @@ class RelationsHandler:
         # while others need more processing during serialization.
         aggregations = BundledAggregations()
 
-        annotations = await self._main_store.get_aggregation_groups_for_event(
-            event_id, room_id
+        annotations = await self.get_annotations_for_event(
+            event_id, room_id, ignored_users=ignored_users
         )
         if annotations:
             aggregations.annotations = {"chunk": annotations}
 
-        references, next_token = await self._main_store.get_relations_for_event(
-            event_id, event, room_id, RelationTypes.REFERENCE, direction="f"
+        references, next_token = await self.get_relations_for_event(
+            event_id,
+            event,
+            room_id,
+            RelationTypes.REFERENCE,
+            ignored_users=ignored_users,
         )
         if references:
             aggregations.references = {
-                "chunk": [{"event_id": event_id} for event_id in references]
+                "chunk": [{"event_id": event.event_id} for event in references]
             }
 
             if next_token:
@@ -216,6 +314,99 @@ class RelationsHandler:
         # Store the bundled aggregations in the event metadata for later use.
         return aggregations
 
+    async def get_threads_for_events(
+        self, event_ids: Collection[str], user_id: str, ignored_users: FrozenSet[str]
+    ) -> Dict[str, _ThreadAggregation]:
+        """Get the bundled aggregations for threads for the requested events.
+
+        Args:
+            event_ids: Events to get aggregations for threads.
+            user_id: The user requesting the bundled aggregations.
+            ignored_users: The users ignored by the requesting user.
+
+        Returns:
+            A dictionary mapping event ID to the thread information.
+
+            May not contain a value for all requested event IDs.
+        """
+        user = UserID.from_string(user_id)
+
+        # Fetch thread summaries.
+        summaries = await self._main_store.get_thread_summaries(event_ids)
+
+        # Only fetch participated for a limited selection based on what had
+        # summaries.
+        thread_event_ids = [
+            event_id for event_id, summary in summaries.items() if summary
+        ]
+        participated = await self._main_store.get_threads_participated(
+            thread_event_ids, user_id
+        )
+
+        # Then subtract off the results for any ignored users.
+        ignored_results = await self._main_store.get_threaded_messages_per_user(
+            thread_event_ids, ignored_users
+        )
+
+        # A map of event ID to the thread aggregation.
+        results = {}
+
+        for event_id, summary in summaries.items():
+            if summary:
+                thread_count, latest_thread_event, edit = summary
+
+                # Subtract off the count of any ignored users.
+                for ignored_user in ignored_users:
+                    thread_count -= ignored_results.get((event_id, ignored_user), 0)
+
+                # This is gnarly, but if the latest event is from an ignored user,
+                # attempt to find one that isn't from an ignored user.
+                if latest_thread_event.sender in ignored_users:
+                    room_id = latest_thread_event.room_id
+
+                    # If the root event is not found, something went wrong, do
+                    # not include a summary of the thread.
+                    event = await self._event_handler.get_event(user, room_id, event_id)
+                    if event is None:
+                        continue
+
+                    potential_events, _ = await self.get_relations_for_event(
+                        event_id,
+                        event,
+                        room_id,
+                        RelationTypes.THREAD,
+                        ignored_users,
+                    )
+
+                    # If all found events are from ignored users, do not include
+                    # a summary of the thread.
+                    if not potential_events:
+                        continue
+
+                    # The *last* event returned is the one that is cared about.
+                    event = await self._event_handler.get_event(
+                        user, room_id, potential_events[-1].event_id
+                    )
+                    # It is unexpected that the event will not exist.
+                    if event is None:
+                        logger.warning(
+                            "Unable to fetch latest event in a thread with event ID: %s",
+                            potential_events[-1].event_id,
+                        )
+                        continue
+                    latest_thread_event = event
+
+                results[event_id] = _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.
+                    current_user_participated=participated[event_id],
+                )
+
+        return results
+
     async def get_bundled_aggregations(
         self, events: Iterable[EventBase], user_id: str
     ) -> Dict[str, BundledAggregations]:
@@ -239,13 +430,21 @@ class RelationsHandler:
         # event ID -> bundled aggregation in non-serialized form.
         results: Dict[str, BundledAggregations] = {}
 
+        # Fetch any ignored users of the requesting user.
+        ignored_users = await self._main_store.ignored_users(user_id)
+
         # Fetch other relations per event.
         for event in events_by_id.values():
-            event_result = await self._get_bundled_aggregation_for_event(event, user_id)
+            event_result = await self._get_bundled_aggregation_for_event(
+                event, ignored_users
+            )
             if event_result:
                 results[event.event_id] = event_result
 
         # Fetch any edits (but not for redacted events).
+        #
+        # Note that there is no use in limiting edits by ignored users since the
+        # parent event should be ignored in the first place if the user is ignored.
         edits = await self._main_store.get_applicable_edits(
             [
                 event_id
@@ -256,25 +455,10 @@ class RelationsHandler:
         for event_id, edit in edits.items():
             results.setdefault(event_id, BundledAggregations()).replace = edit
 
-        # Fetch thread summaries.
-        summaries = await self._main_store.get_thread_summaries(events_by_id.keys())
-        # Only fetch participated for a limited selection based on what had
-        # summaries.
-        participated = await self._main_store.get_threads_participated(
-            [event_id for event_id, summary in summaries.items() if summary], user_id
+        threads = await self.get_threads_for_events(
+            events_by_id.keys(), user_id, ignored_users
         )
-        for event_id, summary in summaries.items():
-            if 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.
-                    current_user_participated=participated[event_id],
-                )
+        for event_id, thread in threads.items():
+            results.setdefault(event_id, BundledAggregations()).thread = thread
 
         return results
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 64a7808140..db929ef523 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -17,6 +17,7 @@ from typing import (
     TYPE_CHECKING,
     Collection,
     Dict,
+    FrozenSet,
     Iterable,
     List,
     Optional,
@@ -26,6 +27,8 @@ from typing import (
     cast,
 )
 
+import attr
+
 from synapse.api.constants import RelationTypes
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
@@ -46,6 +49,19 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class _RelatedEvent:
+    """
+    Contains enough information about a related event in order to properly filter
+    events from ignored users.
+    """
+
+    # The event ID of the related event.
+    event_id: str
+    # The sender of the related event.
+    sender: str
+
+
 class RelationsWorkerStore(SQLBaseStore):
     def __init__(
         self,
@@ -70,7 +86,7 @@ class RelationsWorkerStore(SQLBaseStore):
         direction: str = "b",
         from_token: Optional[StreamToken] = None,
         to_token: Optional[StreamToken] = None,
-    ) -> Tuple[List[str], Optional[StreamToken]]:
+    ) -> Tuple[List[_RelatedEvent], Optional[StreamToken]]:
         """Get a list of relations for an event, ordered by topological ordering.
 
         Args:
@@ -88,7 +104,7 @@ class RelationsWorkerStore(SQLBaseStore):
 
         Returns:
             A tuple of:
-                A list of related event IDs
+                A list of related event IDs & their senders.
 
                 The next stream token, if one exists.
         """
@@ -131,7 +147,7 @@ class RelationsWorkerStore(SQLBaseStore):
             order = "ASC"
 
         sql = """
-            SELECT event_id, relation_type, topological_ordering, stream_ordering
+            SELECT event_id, relation_type, sender, topological_ordering, stream_ordering
             FROM event_relations
             INNER JOIN events USING (event_id)
             WHERE %s
@@ -145,7 +161,7 @@ class RelationsWorkerStore(SQLBaseStore):
 
         def _get_recent_references_for_event_txn(
             txn: LoggingTransaction,
-        ) -> Tuple[List[str], Optional[StreamToken]]:
+        ) -> Tuple[List[_RelatedEvent], Optional[StreamToken]]:
             txn.execute(sql, where_args + [limit + 1])
 
             last_topo_id = None
@@ -155,9 +171,9 @@ class RelationsWorkerStore(SQLBaseStore):
                 # Do not include edits for redacted events as they leak event
                 # content.
                 if not is_redacted or row[1] != RelationTypes.REPLACE:
-                    events.append(row[0])
-                last_topo_id = row[2]
-                last_stream_id = row[3]
+                    events.append(_RelatedEvent(row[0], row[2]))
+                last_topo_id = row[3]
+                last_stream_id = row[4]
 
             # If there are more events, generate the next pagination key.
             next_token = None
@@ -267,7 +283,7 @@ class RelationsWorkerStore(SQLBaseStore):
             `type`, `key` and `count` fields.
         """
 
-        where_args = [
+        args = [
             event_id,
             room_id,
             RelationTypes.ANNOTATION,
@@ -287,7 +303,7 @@ class RelationsWorkerStore(SQLBaseStore):
         def _get_aggregation_groups_for_event_txn(
             txn: LoggingTransaction,
         ) -> List[JsonDict]:
-            txn.execute(sql, where_args)
+            txn.execute(sql, args)
 
             return [{"type": row[0], "key": row[1], "count": row[2]} for row in txn]
 
@@ -295,6 +311,63 @@ class RelationsWorkerStore(SQLBaseStore):
             "get_aggregation_groups_for_event", _get_aggregation_groups_for_event_txn
         )
 
+    async def get_aggregation_groups_for_users(
+        self,
+        event_id: str,
+        room_id: str,
+        limit: int,
+        users: FrozenSet[str] = frozenset(),
+    ) -> Dict[Tuple[str, str], int]:
+        """Fetch the partial aggregations for an event for specific users.
+
+        This is used, in conjunction with get_aggregation_groups_for_event, to
+        remove information from the results for ignored users.
+
+        Args:
+            event_id: Fetch events that relate to this event ID.
+            room_id: The room the event belongs to.
+            limit: Only fetch the `limit` groups.
+            users: The users to fetch information for.
+
+        Returns:
+            A map of (event type, aggregation key) to a count of users.
+        """
+
+        if not users:
+            return {}
+
+        args: List[Union[str, int]] = [
+            event_id,
+            room_id,
+            RelationTypes.ANNOTATION,
+        ]
+
+        users_sql, users_args = make_in_list_sql_clause(
+            self.database_engine, "sender", users
+        )
+        args.extend(users_args)
+
+        sql = f"""
+            SELECT type, aggregation_key, COUNT(DISTINCT sender)
+            FROM event_relations
+            INNER JOIN events USING (event_id)
+            WHERE relates_to_id = ? AND room_id = ? AND relation_type = ? AND {users_sql}
+            GROUP BY relation_type, type, aggregation_key
+            ORDER BY COUNT(*) DESC
+            LIMIT ?
+        """
+
+        def _get_aggregation_groups_for_users_txn(
+            txn: LoggingTransaction,
+        ) -> Dict[Tuple[str, str], int]:
+            txn.execute(sql, args + [limit])
+
+            return {(row[0], row[1]): row[2] for row in txn}
+
+        return await self.db_pool.runInteraction(
+            "get_aggregation_groups_for_users", _get_aggregation_groups_for_users_txn
+        )
+
     @cached()
     def get_applicable_edit(self, event_id: str) -> Optional[EventBase]:
         raise NotImplementedError()
@@ -521,6 +594,67 @@ class RelationsWorkerStore(SQLBaseStore):
 
         return summaries
 
+    async def get_threaded_messages_per_user(
+        self,
+        event_ids: Collection[str],
+        users: FrozenSet[str] = frozenset(),
+    ) -> Dict[Tuple[str, str], int]:
+        """Get the number of threaded replies for a set of users.
+
+        This is used, in conjunction with get_thread_summaries, to calculate an
+        accurate count of the replies to a thread by subtracting ignored users.
+
+        Args:
+            event_ids: The events to check for threaded replies.
+            users: The user to calculate the count of their replies.
+
+        Returns:
+            A map of the (event_id, sender) to the count of their replies.
+        """
+        if not users:
+            return {}
+
+        # Fetch the number of threaded replies.
+        sql = """
+            SELECT parent.event_id, child.sender, COUNT(child.event_id) FROM events AS child
+            INNER JOIN event_relations USING (event_id)
+            INNER JOIN events AS parent ON
+                parent.event_id = relates_to_id
+                AND parent.room_id = child.room_id
+            WHERE
+                %s
+                AND %s
+                AND %s
+            GROUP BY parent.event_id, child.sender
+        """
+
+        def _get_threaded_messages_per_user_txn(
+            txn: LoggingTransaction,
+        ) -> Dict[Tuple[str, str], int]:
+            users_sql, users_args = make_in_list_sql_clause(
+                self.database_engine, "child.sender", users
+            )
+            events_clause, events_args = make_in_list_sql_clause(
+                txn.database_engine, "relates_to_id", event_ids
+            )
+
+            if self._msc3440_enabled:
+                relations_clause = "(relation_type = ? OR relation_type = ?)"
+                relations_args = [RelationTypes.THREAD, RelationTypes.UNSTABLE_THREAD]
+            else:
+                relations_clause = "relation_type = ?"
+                relations_args = [RelationTypes.THREAD]
+
+            txn.execute(
+                sql % (users_sql, events_clause, relations_clause),
+                users_args + events_args + relations_args,
+            )
+            return {(row[0], row[1]): row[2] for row in txn}
+
+        return await self.db_pool.runInteraction(
+            "get_threaded_messages_per_user", _get_threaded_messages_per_user_txn
+        )
+
     @cached()
     def get_thread_participated(self, event_id: str, user_id: str) -> bool:
         raise NotImplementedError()
diff --git a/tests/rest/client/test_relations.py b/tests/rest/client/test_relations.py
index 2f2ec3a685..6fabada8b3 100644
--- a/tests/rest/client/test_relations.py
+++ b/tests/rest/client/test_relations.py
@@ -1137,16 +1137,27 @@ class RelationIgnoredUserTestCase(BaseRelationsTestCase):
     """Relations sent from an ignored user should be ignored."""
 
     def _test_ignored_user(
-        self, allowed_event_ids: List[str], ignored_event_ids: List[str]
-    ) -> None:
+        self,
+        relation_type: str,
+        allowed_event_ids: List[str],
+        ignored_event_ids: List[str],
+    ) -> Tuple[JsonDict, JsonDict]:
         """
         Fetch the relations and ensure they're all there, then ignore user2, and
         repeat.
+
+        Returns:
+            A tuple of two JSON dictionaries, each are bundled aggregations, the
+            first is from before the user is ignored, and the second is after.
         """
         # Get the relations.
         event_ids = self._get_related_events()
         self.assertCountEqual(event_ids, allowed_event_ids + ignored_event_ids)
 
+        # And the bundled aggregations.
+        before_aggregations = self._get_bundled_aggregations()
+        self.assertIn(relation_type, before_aggregations)
+
         # Ignore user2 and re-do the requests.
         self.get_success(
             self.store.add_account_data_for_user(
@@ -1160,6 +1171,12 @@ class RelationIgnoredUserTestCase(BaseRelationsTestCase):
         event_ids = self._get_related_events()
         self.assertCountEqual(event_ids, allowed_event_ids)
 
+        # And the bundled aggregations.
+        after_aggregations = self._get_bundled_aggregations()
+        self.assertIn(relation_type, after_aggregations)
+
+        return before_aggregations[relation_type], after_aggregations[relation_type]
+
     def test_annotation(self) -> None:
         """Annotations should ignore"""
         # Send 2 from us, 2 from the to be ignored user.
@@ -1184,7 +1201,26 @@ class RelationIgnoredUserTestCase(BaseRelationsTestCase):
         )
         ignored_event_ids.append(channel.json_body["event_id"])
 
-        self._test_ignored_user(allowed_event_ids, ignored_event_ids)
+        before_aggregations, after_aggregations = self._test_ignored_user(
+            RelationTypes.ANNOTATION, allowed_event_ids, ignored_event_ids
+        )
+
+        self.assertCountEqual(
+            before_aggregations["chunk"],
+            [
+                {"type": "m.reaction", "key": "a", "count": 2},
+                {"type": "m.reaction", "key": "b", "count": 1},
+                {"type": "m.reaction", "key": "c", "count": 1},
+            ],
+        )
+
+        self.assertCountEqual(
+            after_aggregations["chunk"],
+            [
+                {"type": "m.reaction", "key": "a", "count": 1},
+                {"type": "m.reaction", "key": "b", "count": 1},
+            ],
+        )
 
     def test_reference(self) -> None:
         """Annotations should ignore"""
@@ -1196,7 +1232,18 @@ class RelationIgnoredUserTestCase(BaseRelationsTestCase):
         )
         ignored_event_ids = [channel.json_body["event_id"]]
 
-        self._test_ignored_user(allowed_event_ids, ignored_event_ids)
+        before_aggregations, after_aggregations = self._test_ignored_user(
+            RelationTypes.REFERENCE, allowed_event_ids, ignored_event_ids
+        )
+
+        self.assertCountEqual(
+            [e["event_id"] for e in before_aggregations["chunk"]],
+            allowed_event_ids + ignored_event_ids,
+        )
+
+        self.assertCountEqual(
+            [e["event_id"] for e in after_aggregations["chunk"]], allowed_event_ids
+        )
 
     def test_thread(self) -> None:
         """Annotations should ignore"""
@@ -1208,7 +1255,23 @@ class RelationIgnoredUserTestCase(BaseRelationsTestCase):
         )
         ignored_event_ids = [channel.json_body["event_id"]]
 
-        self._test_ignored_user(allowed_event_ids, ignored_event_ids)
+        before_aggregations, after_aggregations = self._test_ignored_user(
+            RelationTypes.THREAD, allowed_event_ids, ignored_event_ids
+        )
+
+        self.assertEqual(before_aggregations["count"], 2)
+        self.assertTrue(before_aggregations["current_user_participated"])
+        # The latest thread event has some fields that don't matter.
+        self.assertEqual(
+            before_aggregations["latest_event"]["event_id"], ignored_event_ids[0]
+        )
+
+        self.assertEqual(after_aggregations["count"], 1)
+        self.assertTrue(after_aggregations["current_user_participated"])
+        # The latest thread event has some fields that don't matter.
+        self.assertEqual(
+            after_aggregations["latest_event"]["event_id"], allowed_event_ids[0]
+        )
 
 
 class RelationRedactionTestCase(BaseRelationsTestCase):