Failure running `xmllint` on HTML builds about xeps HOT 2 CLOSED

The

! xmllint --nonet --noout --noent --loaddtd --xpath "//img/@src[not(starts-with(., 'data:'))]" $< 2>/dev/null && true

line was added by Sam in ff0ef6d referenzing #212.

This line fails now. I am not sure which entity changed here the behavior, could be xmllint von libxml2 or GNU Make. The whole construct raises two or three questions.

What I found so far is that xmllint's man page says: In case of an empty node set the "XPath set is empty" result will be shown and an error exit code will be returned.

However:

$ xmllint --loaddtd --xpath "//img/@src[not(starts-with(., 'data:'))]" xep-0033.xml
XPath set is empty
$ echo $?
0

I have reported this upstream as https://gitlab.gnome.org/GNOME/libxml2/-/issues/673

from xeps.

FTR, it was xmllint that broke API starting with libxml 2.11.

from xeps.