Do not require messages, but no-op if it is not available.

synapse/rest/client/v2_alpha/sendtodevice.py

@@ -14,10 +14,9 @@
 # limitations under the License.
 
 import logging
-from typing import Tuple
 
 from synapse.http import servlet
-from synapse.http.servlet import assert_params_in_dict, parse_json_object_from_request
+from synapse.http.servlet import parse_json_object_from_request
 from synapse.logging.opentracing import set_tag, trace
 from synapse.rest.client.transactions import HttpTransactionCache
 
@@ -54,16 +53,18 @@ async def _put(self, request, message_type, txn_id):
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         content = parse_json_object_from_request(request)
-        assert_params_in_dict(content, ("messages",))
 
-        sender_user_id = requester.user.to_string()
+        # Messages is optional, but there is nothing for the server to do if it
+        # is not provided (or is empty).
+        messages = content.get("messages")
+        if messages:
+            sender_user_id = requester.user.to_string()
 
-        await self.device_message_handler.send_device_message(
-            sender_user_id, message_type, content["messages"]
-        )
+            await self.device_message_handler.send_device_message(
+                sender_user_id, message_type, messages
+            )
 
-        response = (200, {})  # type: Tuple[int, dict]
-        return response
+        return 200, {}
 
 
 def register_servlets(hs, http_server):