Fix error handling for rooms whose versions are unknown. (#5219)

If we remove support for a particular room version, we should behave more
gracefully. This should make client requests fail with a 400 rather than a 500,
and will ignore individiual PDUs in a federation transaction, rather than the
whole transaction.

1 files changed, 15 insertions, 1 deletions

diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index ff89259dec..e91697049c 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -328,9 +328,23 @@ class RoomKeysVersionError(SynapseError):
         self.current_version = current_version
 
 
+class UnsupportedRoomVersionError(SynapseError):
+    """The client's request to create a room used a room version that the server does
+    not support."""
+    def __init__(self):
+        super(UnsupportedRoomVersionError, self).__init__(
+            code=400,
+            msg="Homeserver does not support this room version",
+            errcode=Codes.UNSUPPORTED_ROOM_VERSION,
+        )
+
+
 class IncompatibleRoomVersionError(SynapseError):
-    """A server is trying to join a room whose version it does not support."""
+    """A server is trying to join a room whose version it does not support.
 
+    Unlike UnsupportedRoomVersionError, it is specific to the case of the make_join
+    failing.
+    """
     def __init__(self, room_version):
         super(IncompatibleRoomVersionError, self).__init__(
             code=400,