As discovered in
QPID-8113 if a client attempts to attach to a source using an unknown filter type (i.e. an unrecognised descriptor) the broker responds with a decode error similar to
[0x555941994670]:0 <- @close(24) [error=@error(29) [condition=:"amqp:decode-error", description="Expected key type is 'Filter' but got 'DescribedType'"]]
Instead the broker should simply fail to attach (i.e. attach with source=null) and then immediately detach with a not-implemented error.