dovecot - Apr 2013 - CATENATE allows empty messages

Dovecot-2.2.1 allows empty messages to be APPENDed when using CATENATE:
b1 append inbox catenate (text {0+}     
)
b1 OK [APPENDUID 1366726248 12] Append completed.

Contrast this with regular APPEND:
b2 append inbox {0+}
b2 NO Can't save a zero byte message.

Note that zero-size literals are OK but zero-size messages are not.  So while
"b1" above should fail like "b2", this should continue to
succeed:
b3 append inbox catenate (text {0+}
 text {8+}
foobar
)
b3 OK [APPENDUID 1366726248 13] Append completed.

Something ate an important leading space from my message.
> b3 append inbox catenate (text {0+}
> text {8+}
> foobar
> )
> b3 OK [APPENDUID 1366726248 13] Append completed.
There was and should be a single space before the "text {8+}" above.

On 29.4.2013, at 21.40, Mike Abbott <michael.abbott at apple.com> wrote:
> Dovecot-2.2.1 allows empty messages to be APPENDed when using CATENATE:
> b1 append inbox catenate (text {0+}     
> )
> b1 OK [APPENDUID 1366726248 12] Append completed.
> 
> Contrast this with regular APPEND:
> b2 append inbox {0+}
> b2 NO Can't save a zero byte message.
> 
> Note that zero-size literals are OK but zero-size messages are not.  So
while "b1" above should fail like "b2", this should continue
to succeed:
> b3 append inbox catenate (text {0+}
> text {8+}
> foobar
> )
> b3 OK [APPENDUID 1366726248 13] Append completed.
This could be changed I guess, but I don't think it's a bug. I don't
see anything in RFC 3501 prohibiting saving empty messages. Only the MULTIAPPEND
RFC says:

      A zero-length message literal argument is an error, and MUST
      return a NO.  This can be used to cancel the append.

But that doesn't prohibit zero-length CATENATE parameters.