Allow modules to create and send events into rooms (#8479)

This PR allows Synapse modules making use of the `ModuleApi` to create and send non-membership events into a room. This can useful to have modules send messages, or change power levels in a room etc. Note that they must send event through a user that's already in the room.

The non-membership event limitation is currently arbitrary, as it's another chunk of work and not necessary at the moment.

This commit has been cherry-picked from mainline.

tests/module_api/test_api.py

@@ -12,9 +12,13 @@
 # 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 mock import Mock
+
+from synapse.events import EventBase
 from synapse.module_api import ModuleApi
 from synapse.rest import admin
 from synapse.rest.client.v1 import login, room
+from synapse.types import create_requester
 
 from tests.unittest import HomeserverTestCase
 
@@ -29,6 +33,7 @@ class ModuleApiTestCase(HomeserverTestCase):
     def prepare(self, reactor, clock, homeserver):
         self.store = homeserver.get_datastore()
         self.module_api = ModuleApi(homeserver, homeserver.get_auth_handler())
+        self.event_creation_handler = homeserver.get_event_creation_handler()
 
     def test_can_register_user(self):
         """Tests that an external module can register a user"""
@@ -60,6 +65,93 @@ class ModuleApiTestCase(HomeserverTestCase):
         displayname = self.get_success(self.store.get_profile_displayname("bob"))
         self.assertEqual(displayname, "Bobberino")
 
+    def test_sending_events_into_room(self):
+        """Tests that a module can send events into a room"""
+        # Mock out create_and_send_nonmember_event to check whether events are being sent
+        self.event_creation_handler.create_and_send_nonmember_event = Mock(
+            spec=[],
+            side_effect=self.event_creation_handler.create_and_send_nonmember_event,
+        )
+
+        # Create a user and room to play with
+        user_id = self.register_user("summer", "monkey")
+        tok = self.login("summer", "monkey")
+        room_id = self.helper.create_room_as(user_id, tok=tok)
+
+        # Create and send a non-state event
+        content = {"body": "I am a puppet", "msgtype": "m.text"}
+        event_dict = {
+            "room_id": room_id,
+            "type": "m.room.message",
+            "content": content,
+            "sender": user_id,
+        }
+        event = self.get_success(
+            self.module_api.create_and_send_event_into_room(event_dict)
+        )  # type: EventBase
+        self.assertEqual(event.sender, user_id)
+        self.assertEqual(event.type, "m.room.message")
+        self.assertEqual(event.room_id, room_id)
+        self.assertFalse(hasattr(event, "state_key"))
+        self.assertDictEqual(event.content, content)
+
+        # Check that the event was sent
+        self.event_creation_handler.create_and_send_nonmember_event.assert_called_with(
+            create_requester(user_id), event_dict, ratelimit=False,
+        )
+
+        # Create and send a state event
+        content = {
+            "events_default": 0,
+            "users": {user_id: 100},
+            "state_default": 50,
+            "users_default": 0,
+            "events": {"test.event.type": 25},
+        }
+        event_dict = {
+            "room_id": room_id,
+            "type": "m.room.power_levels",
+            "content": content,
+            "sender": user_id,
+            "state_key": "",
+        }
+        event = self.get_success(
+            self.module_api.create_and_send_event_into_room(event_dict)
+        )  # type: EventBase
+        self.assertEqual(event.sender, user_id)
+        self.assertEqual(event.type, "m.room.power_levels")
+        self.assertEqual(event.room_id, room_id)
+        self.assertEqual(event.state_key, "")
+        self.assertDictEqual(event.content, content)
+
+        # Check that the event was sent
+        self.event_creation_handler.create_and_send_nonmember_event.assert_called_with(
+            create_requester(user_id),
+            {
+                "type": "m.room.power_levels",
+                "content": content,
+                "room_id": room_id,
+                "sender": user_id,
+                "state_key": "",
+            },
+            ratelimit=False,
+        )
+
+        # Check that we can't send membership events
+        content = {
+            "membership": "leave",
+        }
+        event_dict = {
+            "room_id": room_id,
+            "type": "m.room.member",
+            "content": content,
+            "sender": user_id,
+            "state_key": user_id,
+        }
+        self.get_failure(
+            self.module_api.create_and_send_event_into_room(event_dict), Exception
+        )
+
     def test_public_rooms(self):
         """Tests that a room can be added and removed from the public rooms list,
         as well as have its public rooms directory state queried.