Allow retrieving the relations of a redacted event. (#12130)

This is allowed per MSC2675, although the original implementation did
not allow for it and would return an empty chunk / not bundle aggregations.

The main thing to improve is that the various caches get cleared properly
when an event is redacted, and that edits must not leak if the original
event is redacted (as that would presumably leak something similar to
the original event content).

1 files changed, 38 insertions, 44 deletions

diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py

index 07fa1cdd4c..d9a6be43f7 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -27,7 +27,7 @@ from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_integer, parse_string
 from synapse.http.site import SynapseRequest
 from synapse.rest.client._base import client_patterns
-from synapse.storage.relations import AggregationPaginationToken, PaginationChunk
+from synapse.storage.relations import AggregationPaginationToken
 from synapse.types import JsonDict, StreamToken
 
 if TYPE_CHECKING:
@@ -82,28 +82,25 @@ class RelationPaginationServlet(RestServlet):
         from_token_str = parse_string(request, "from")
         to_token_str = parse_string(request, "to")
 
-        if event.internal_metadata.is_redacted():
-            # If the event is redacted, return an empty list of relations
-            pagination_chunk = PaginationChunk(chunk=[])
-        else:
-            # Return the relations
-            from_token = None
-            if from_token_str:
-                from_token = await StreamToken.from_string(self.store, from_token_str)
-            to_token = None
-            if to_token_str:
-                to_token = await StreamToken.from_string(self.store, to_token_str)
-
-            pagination_chunk = await self.store.get_relations_for_event(
-                event_id=parent_id,
-                room_id=room_id,
-                relation_type=relation_type,
-                event_type=event_type,
-                limit=limit,
-                direction=direction,
-                from_token=from_token,
-                to_token=to_token,
-            )
+        # Return the relations
+        from_token = None
+        if from_token_str:
+            from_token = await StreamToken.from_string(self.store, from_token_str)
+        to_token = None
+        if to_token_str:
+            to_token = await StreamToken.from_string(self.store, to_token_str)
+
+        pagination_chunk = await self.store.get_relations_for_event(
+            event_id=parent_id,
+            event=event,
+            room_id=room_id,
+            relation_type=relation_type,
+            event_type=event_type,
+            limit=limit,
+            direction=direction,
+            from_token=from_token,
+            to_token=to_token,
+        )
 
         events = await self.store.get_events_as_list(
             [c["event_id"] for c in pagination_chunk.chunk]
@@ -193,27 +190,23 @@ class RelationAggregationPaginationServlet(RestServlet):
         from_token_str = parse_string(request, "from")
         to_token_str = parse_string(request, "to")
 
-        if event.internal_metadata.is_redacted():
-            # If the event is redacted, return an empty list of relations
-            pagination_chunk = PaginationChunk(chunk=[])
-        else:
-            # Return the relations
-            from_token = None
-            if from_token_str:
-                from_token = AggregationPaginationToken.from_string(from_token_str)
-
-            to_token = None
-            if to_token_str:
-                to_token = AggregationPaginationToken.from_string(to_token_str)
-
-            pagination_chunk = await self.store.get_aggregation_groups_for_event(
-                event_id=parent_id,
-                room_id=room_id,
-                event_type=event_type,
-                limit=limit,
-                from_token=from_token,
-                to_token=to_token,
-            )
+        # Return the relations
+        from_token = None
+        if from_token_str:
+            from_token = AggregationPaginationToken.from_string(from_token_str)
+
+        to_token = None
+        if to_token_str:
+            to_token = AggregationPaginationToken.from_string(to_token_str)
+
+        pagination_chunk = await self.store.get_aggregation_groups_for_event(
+            event_id=parent_id,
+            room_id=room_id,
+            event_type=event_type,
+            limit=limit,
+            from_token=from_token,
+            to_token=to_token,
+        )
 
         return 200, await pagination_chunk.to_dict(self.store)
 
@@ -295,6 +288,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
 
         result = await self.store.get_relations_for_event(
             event_id=parent_id,
+            event=event,
             room_id=room_id,
             relation_type=relation_type,
             event_type=event_type,