Change default room version to 10. Implements MSC3904

changelog.d/14111.feature

@@ -0,0 +1 @@
+Update the default room version to [v10](https://spec.matrix.org/v1.5/rooms/v10/) ([MSC 3904](https://github.com/matrix-org/matrix-spec-proposals/pull/3904)). Contributed by @FSG-Cat.

docs/usage/configuration/config_documentation.md

@@ -295,7 +295,9 @@ Known room versions are listed [here](https://spec.matrix.org/latest/rooms/#comp
 For example, for room version 1, `default_room_version` should be set
 to "1".
 
-Currently defaults to "9".
+Currently defaults to ["10"](https://spec.matrix.org/v1.5/rooms/v10/).
+
+_Changed in Synapse 1.76:_ the default version room version was increased from [9](https://spec.matrix.org/v1.5/rooms/v9/) to [10](https://spec.matrix.org/v1.5/rooms/v10/).
 
 Example configuration:
 ```yaml

synapse/config/server.py

@@ -151,7 +151,7 @@ def generate_ip_set(
     "fec0::/10",
 ]
 
-DEFAULT_ROOM_VERSION = "9"
+DEFAULT_ROOM_VERSION = "10"
 
 ROOM_COMPLEXITY_TOO_GREAT = (
     "Your homeserver is unable to join rooms this large or complex. "

tests/rest/client/test_upgrade_room.py

@@ -199,9 +199,15 @@ def test_power_levels_tombstone(self) -> None:
 
     def test_stringy_power_levels(self) -> None:
         """The room upgrade converts stringy power levels to proper integers."""
+        # Create a room on room version < 10.
+        room_id = self.helper.create_room_as(
+            self.creator, tok=self.creator_token, room_version="9"
+        )
+        self.helper.join(room_id, self.other, tok=self.other_token)
+
         # Retrieve the room's current power levels.
         power_levels = self.helper.get_state(
-            self.room_id,
+            room_id,
             "m.room.power_levels",
             tok=self.creator_token,
         )
@@ -217,14 +223,14 @@ def test_stringy_power_levels(self) -> None:
             # conscience, we ought to ensure it's upgrading from a sufficiently old
             # version of room.
             self.helper.send_state(
-                self.room_id,
+                room_id,
                 "m.room.power_levels",
                 body=power_levels,
                 tok=self.creator_token,
             )
 
         # Upgrade the room. Check the homeserver reports success.
-        channel = self._upgrade_room()
+        channel = self._upgrade_room(room_id=room_id)
         self.assertEqual(200, channel.code, channel.result)
 
         # Extract the new room ID.