Add new module API for adding custom fields to events unsigned section (#16549)

tests/module_api/test_event_unsigned_addition.py

@@ -0,0 +1,59 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.events import EventBase
+from synapse.rest import admin, login, room
+from synapse.server import HomeServer
+from synapse.types import JsonDict
+from synapse.util import Clock
+
+from tests.unittest import HomeserverTestCase
+
+
+class EventUnsignedAdditionTestCase(HomeserverTestCase):
+    servlets = [
+        room.register_servlets,
+        admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(
+        self, reactor: MemoryReactor, clock: Clock, homeserver: HomeServer
+    ) -> None:
+        self._store = homeserver.get_datastores().main
+        self._module_api = homeserver.get_module_api()
+        self._account_data_mgr = self._module_api.account_data_manager
+
+    def test_annotate_event(self) -> None:
+        """Test that we can annotate an event when we request it from the
+        server.
+        """
+
+        async def add_unsigned_event(event: EventBase) -> JsonDict:
+            return {"test_key": event.event_id}
+
+        self._module_api.register_add_extra_fields_to_unsigned_client_event_callbacks(
+            add_field_to_unsigned_callback=add_unsigned_event
+        )
+
+        user_id = self.register_user("user", "password")
+        token = self.login("user", "password")
+
+        room_id = self.helper.create_room_as(user_id, tok=token)
+        result = self.helper.send(room_id, "Hello!", tok=token)
+        event_id = result["event_id"]
+
+        event_json = self.helper.get_event(room_id, event_id, tok=token)
+        self.assertEqual(event_json["unsigned"].get("test_key"), event_id)