Make minor clarifications to the error messages given when we fail to join a room via any server. (#13160)

1 files changed, 7 insertions, 1 deletions

diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py

index 02276ed995..6a8d76529b 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -725,6 +725,12 @@ class FederationClient(FederationBase):
         if failover_errcodes is None:
             failover_errcodes = ()
 
+        if not destinations:
+            # Give a bit of a clearer message if no servers were specified at all.
+            raise SynapseError(
+                502, f"Failed to {description} via any server: No servers specified."
+            )
+
         for destination in destinations:
             if destination == self.server_name:
                 continue
@@ -774,7 +780,7 @@ class FederationClient(FederationBase):
                     "Failed to %s via %s", description, destination, exc_info=True
                 )
 
-        raise SynapseError(502, "Failed to %s via any server" % (description,))
+        raise SynapseError(502, f"Failed to {description} via any server")
 
     async def make_membership_event(
         self,