\NewDocumentCommand{\xxx}{ e{_} }{#1}
$\xxx_1$
Here _ shouldn't be parsed as a macro, but rather as a part of an argument of \xxx,
but currently _1 is first gobbled as a macro and \xxx cannot find an argument.
Logic in attach-arguments.ts need to be changed.
Here
_shouldn't be parsed as a macro, but rather as a part of an argument of\xxx,but currently
_1is first gobbled as a macro and\xxxcannot find an argument.Logic in
attach-arguments.tsneed to be changed.