diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 71853caad8..13fa93afb8 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -28,8 +28,14 @@ from typing import (
)
import attr
+from canonicaljson import encode_canonical_json
-from synapse.api.constants import EventContentFields, EventTypes, RelationTypes
+from synapse.api.constants import (
+ MAX_PDU_SIZE,
+ EventContentFields,
+ EventTypes,
+ RelationTypes,
+)
from synapse.api.errors import Codes, SynapseError
from synapse.api.room_versions import RoomVersion
from synapse.types import JsonDict
@@ -674,3 +680,27 @@ def validate_canonicaljson(value: Any) -> None:
elif not isinstance(value, (bool, str)) and value is not None:
# Other potential JSON values (bool, None, str) are safe.
raise SynapseError(400, "Unknown JSON value", Codes.BAD_JSON)
+
+
+def maybe_upsert_event_field(
+ event: EventBase, container: JsonDict, key: str, value: object
+) -> bool:
+ """Upsert an event field, but only if this doesn't make the event too large.
+
+ Returns true iff the upsert took place.
+ """
+ if key in container:
+ old_value: object = container[key]
+ container[key] = value
+ # NB: here and below, we assume that passing a non-None `time_now` argument to
+ # get_pdu_json doesn't increase the size of the encoded result.
+ upsert_okay = len(encode_canonical_json(event.get_pdu_json())) <= MAX_PDU_SIZE
+ if not upsert_okay:
+ container[key] = old_value
+ else:
+ container[key] = value
+ upsert_okay = len(encode_canonical_json(event.get_pdu_json())) <= MAX_PDU_SIZE
+ if not upsert_okay:
+ del container[key]
+
+ return upsert_okay
|
