In file /usr/share/egroupware/calendar/inc/class.calendar_groupdav.inc.php, line 775 to 778, we have this:
$props[] = HTTP_WebDAV_Server::mkprop('supported-report-set',array(
HTTP_WebDAV_Server::mkprop('supported-report',array(
HTTP_WebDAV_Server::mkprop('report',
HTTP_WebDAV_Server::mkprop(groupdav::CALDAV,'calendar-multiget'))))));
Maybe it should be more like this:
$props[] = HTTP_WebDAV_Server::mkprop(groupdav::CALDAV, 'supported-report-set',array(
HTTP_WebDAV_Server::mkprop('supported-report',array(
HTTP_WebDAV_Server::mkprop('report', 'calendar-multiget')))));
In any case where “groupdav::CALDAV” appears as one of the parameters in HTTP_WebDAV_Server::mkprop it always appears as the first of 3 parameters, not the first of 2, so that is appears as an XML attribute not an XML element (for which it is invalid).
I’d like to report this as a bug, but the user registration system for the tracker is broken, so I can’t.