diff --git a/synapse/storage/relations.py b/synapse/storage/relations.py
index de67e305a1..6e216066ab 100644
--- a/synapse/storage/relations.py
+++ b/synapse/storage/relations.py
@@ -17,11 +17,13 @@ import logging
import attr
+from twisted.internet import defer
+
from synapse.api.constants import RelationTypes
from synapse.api.errors import SynapseError
from synapse.storage._base import SQLBaseStore
from synapse.storage.stream import generate_pagination_where_clause
-from synapse.util.caches.descriptors import cached
+from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
logger = logging.getLogger(__name__)
@@ -312,6 +314,59 @@ class RelationsWorkerStore(SQLBaseStore):
"get_aggregation_groups_for_event", _get_aggregation_groups_for_event_txn
)
+ @cachedInlineCallbacks()
+ def get_applicable_edit(self, event_id):
+ """Get the most recent edit (if any) that has happened for the given
+ event.
+
+ Correctly handles checking whether edits were allowed to happen.
+
+ Args:
+ event_id (str): The original event ID
+
+ Returns:
+ Deferred[EventBase|None]: Returns the most recent edit, if any.
+ """
+
+ # We only allow edits for `m.room.message` events that have the same sender
+ # and event type. We can't assert these things during regular event auth so
+ # we have to do the checks post hoc.
+
+ # Fetches latest edit that has the same type and sender as the
+ # original, and is an `m.room.message`.
+ sql = """
+ SELECT edit.event_id FROM events AS edit
+ INNER JOIN event_relations USING (event_id)
+ INNER JOIN events AS original ON
+ original.event_id = relates_to_id
+ AND edit.type = original.type
+ AND edit.sender = original.sender
+ WHERE
+ relates_to_id = ?
+ AND relation_type = ?
+ AND edit.type = 'm.room.message'
+ ORDER by edit.origin_server_ts DESC, edit.event_id DESC
+ LIMIT 1
+ """
+
+ def _get_applicable_edit_txn(txn):
+ txn.execute(
+ sql, (event_id, RelationTypes.REPLACES,)
+ )
+ row = txn.fetchone()
+ if row:
+ return row[0]
+
+ edit_id = yield self.runInteraction(
+ "get_applicable_edit", _get_applicable_edit_txn
+ )
+
+ if not edit_id:
+ return
+
+ edit_event = yield self.get_event(edit_id, allow_none=True)
+ defer.returnValue(edit_event)
+
class RelationsStore(RelationsWorkerStore):
def _handle_event_relations(self, txn, event):
@@ -357,3 +412,6 @@ class RelationsStore(RelationsWorkerStore):
txn.call_after(
self.get_aggregation_groups_for_event.invalidate_many, (parent_id,)
)
+
+ if rel_type == RelationTypes.REPLACES:
+ txn.call_after(self.get_applicable_edit.invalidate, (parent_id,))
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