Document and fix room_config param when user_may_create_room callback is invoked for a room upgrade

changelog.d/18721.bugfix

@@ -0,0 +1 @@
+Fix room upgrade `room_config` argument and documentation for `user_may_create_room` spam-checker callback.

docs/modules/spam_checker_callbacks.md

@@ -195,12 +195,15 @@ _Changed in Synapse v1.132.0: Added the `room_config` argument. Callbacks that o
 async def user_may_create_room(user_id: str, room_config: synapse.module_api.JsonDict) -> Union["synapse.module_api.NOT_SPAM", "synapse.module_api.errors.Codes", bool]
 ```
 
-Called when processing a room creation request.
+Called when processing a room creation or room upgrade request.
 
 The arguments passed to this callback are:
 
 * `user_id`: The Matrix user ID of the user (e.g. `@alice:example.com`).
-* `room_config`: The contents of the body of a [/createRoom request](https://spec.matrix.org/latest/client-server-api/#post_matrixclientv3createroom) as a dictionary.
+* `room_config`: The contents of the body of the [`/createRoom` request](https://spec.matrix.org/v1.15/client-server-api/#post_matrixclientv3createroom) as a dictionary.
+  For a [room upgrade request](https://spec.matrix.org/v1.15/client-server-api/#post_matrixclientv3roomsroomidupgrade) it is a synthesised subset of what an equivalent
+  `/createRoom` request would have looked like. Specifically, it contains the `creation_content` (linking to the previous room) and `initial_state` (containing a
+  subset of the state of the previous room).
 
 The callback must return one of:
   - `synapse.module_api.NOT_SPAM`, to allow the operation. Other callbacks may still 

synapse/handlers/room.py

@@ -597,7 +597,7 @@ async def clone_existing_room(
                 new_room_version,
                 additional_creators=additional_creators,
             )
-        initial_state = {}
+        initial_state: MutableStateMap = {}
 
         # Replicate relevant room events
         types_to_copy: List[Tuple[str, Optional[str]]] = [
@@ -693,14 +693,23 @@ async def clone_existing_room(
                 additional_creators,
             )
 
-        # We construct what the body of a call to /createRoom would look like for passing
-        # to the spam checker. We don't include a preset here, as we expect the
+        # We construct a subset of what the body of a call to /createRoom would look like
+        # for passing to the spam checker. We don't include a preset here, as we expect the
         # initial state to contain everything we need.
+        # TODO: given we are upgrading, it would make sense to pass the room_version
+        # TODO: the preset might be useful too
         spam_check = await self._spam_checker_module_callbacks.user_may_create_room(
             user_id,
             {
                 "creation_content": creation_content,
-                "initial_state": list(initial_state.items()),
+                "initial_state": [
+                    {
+                        "type": state_key[0],
+                        "state_key": state_key[1],
+                        "content": event_content,
+                    }
+                    for state_key, event_content in initial_state.items()
+                ],
             },
         )
         if spam_check != self._spam_checker_module_callbacks.NOT_SPAM:

tests/module_api/test_spamchecker.py

@@ -16,6 +16,7 @@
 
 from twisted.internet.testing import MemoryReactor
 
+from synapse.api.constants import EventContentFields, EventTypes
 from synapse.config.server import DEFAULT_ROOM_VERSION
 from synapse.rest import admin, login, room, room_upgrade_rest_servlet
 from synapse.server import HomeServer
@@ -51,8 +52,8 @@ def create_room(self, content: JsonDict) -> FakeChannel:
 
         return channel
 
-    def test_may_user_create_room(self) -> None:
-        """Test that the may_user_create_room callback is called when a user
+    def test_user_may_create_room(self) -> None:
+        """Test that the user_may_create_room callback is called when a user
         creates a room, and that it receives the correct parameters.
         """
 
@@ -67,16 +68,50 @@ async def user_may_create_room(
             user_may_create_room=user_may_create_room
         )
 
-        channel = self.create_room({"foo": "baa"})
+        expected_room_config = {"foo": "baa"}
+        channel = self.create_room(expected_room_config)
+
         self.assertEqual(channel.code, 200)
         self.assertEqual(self.last_user_id, self.user_id)
-        self.assertEqual(self.last_room_config["foo"], "baa")
+        self.assertEqual(self.last_room_config, expected_room_config)
 
-    def test_may_user_create_room_on_upgrade(self) -> None:
-        """Test that the may_user_create_room callback is called when a room is upgraded."""
+    def test_user_may_create_room_with_initial_state(self) -> None:
+        """Test that the user_may_create_room callback is called when a user
+        creates a room with some initial state events, and that it receives the correct parameters.
+        """
+
+        async def user_may_create_room(
+            user_id: str, room_config: JsonDict
+        ) -> Union[Literal["NOT_SPAM"], Codes]:
+            self.last_room_config = room_config
+            self.last_user_id = user_id
+            return "NOT_SPAM"
+
+        self._module_api.register_spam_checker_callbacks(
+            user_may_create_room=user_may_create_room
+        )
+
+        expected_room_config = {
+            "foo": "baa",
+            "initial_state": [
+                {
+                    "type": EventTypes.Topic,
+                    "content": {EventContentFields.TOPIC: "foo"},
+                }
+            ],
+        }
+        channel = self.create_room(expected_room_config)
+
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(self.last_user_id, self.user_id)
+        self.assertEqual(self.last_room_config, expected_room_config)
+
+    def test_user_may_create_room_on_upgrade(self) -> None:
+        """Test that the user_may_create_room callback is called when a room is upgraded."""
 
         # First, create a room to upgrade.
-        channel = self.create_room({"topic": "foo"})
+        channel = self.create_room({EventContentFields.TOPIC: "foo"})
+
         self.assertEqual(channel.code, 200)
         room_id = channel.json_body["room_id"]
 
@@ -107,13 +142,15 @@ async def user_may_create_room(
         # Check that the initial state received by callback contains the topic event.
         self.assertTrue(
             any(
-                event[0][0] == "m.room.topic" and event[1].get("topic") == "foo"
+                event.get("type") == EventTypes.Topic
+                and event.get("state_key") == ""
+                and event.get("content").get(EventContentFields.TOPIC) == "foo"
                 for event in self.last_room_config["initial_state"]
             )
         )
 
-    def test_may_user_create_room_disallowed(self) -> None:
-        """Test that the codes response from may_user_create_room callback is respected
+    def test_user_may_create_room_disallowed(self) -> None:
+        """Test that the codes response from user_may_create_room callback is respected
         and returned via the API.
         """
 
@@ -128,14 +165,16 @@ async def user_may_create_room(
             user_may_create_room=user_may_create_room
         )
 
-        channel = self.create_room({"foo": "baa"})
+        expected_room_config = {"foo": "baa"}
+        channel = self.create_room(expected_room_config)
+
         self.assertEqual(channel.code, 403)
         self.assertEqual(channel.json_body["errcode"], Codes.UNAUTHORIZED)
         self.assertEqual(self.last_user_id, self.user_id)
-        self.assertEqual(self.last_room_config["foo"], "baa")
+        self.assertEqual(self.last_room_config, expected_room_config)
 
-    def test_may_user_create_room_compatibility(self) -> None:
-        """Test that the may_user_create_room callback is called when a user
+    def test_user_may_create_room_compatibility(self) -> None:
+        """Test that the user_may_create_room callback is called when a user
         creates a room for a module that uses the old callback signature
         (without the `room_config` parameter)
         """
@@ -151,6 +190,7 @@ async def user_may_create_room(
         )
 
         channel = self.create_room({"foo": "baa"})
+
         self.assertEqual(channel.code, 200)
         self.assertEqual(self.last_user_id, self.user_id)
 
@@ -178,6 +218,7 @@ async def user_may_send_state_event(
         )
 
         channel = self.create_room({})
+
         self.assertEqual(channel.code, 200)
 
         room_id = channel.json_body["room_id"]
@@ -222,6 +263,7 @@ async def user_may_send_state_event(
         )
 
         channel = self.create_room({})
+
         self.assertEqual(channel.code, 200)
 
         room_id = channel.json_body["room_id"]