Merge remote-tracking branch 'upstream/release-v1.39'

synapse/handlers/sync.py

@@ -1092,6 +1092,10 @@ class SyncHandler:
         one_time_key_counts: JsonDict = {}
         unused_fallback_key_types: List[str] = []
         if device_id:
+            # TODO: We should have a way to let clients differentiate between the states of:
+            #   * no change in OTK count since the provided since token
+            #   * the server has zero OTKs left for this device
+            #  Spec issue: https://github.com/matrix-org/matrix-doc/issues/3298
             one_time_key_counts = await self.store.count_e2e_one_time_keys(
                 user_id, device_id
             )