xml_is_document and selective pg_re_throw

Hi,

Consider:

SELECT xml '<foo>bar</foo><bar>foo</bar>' IS DOCUMENT;

And I was looking at xml_is_document() source code. It calls xml_parse
which throws an error with code set to ERRCODE_INVALID_XML_DOCUMENT. The
catch block of xml_parse then rethrows.

Now xml_is_document does a selective rethrow only if the error is not
ERRCODE_INVALID_XML_DOCUMENT. I can understand that this function does this
to return true/false, but doesn't this behavior of not propagating the
error up all the way dangerous? InterruptHoldoffCount inconsistencies for
instance?

A better way would have been to modify xml_parse to take an additional
boolean argument "to_rethrow" and not to rethrow if that is false?
Thoughts?

Regards,
Nikhils