reference commands are not correctly tagged

[u-fischer]

Reference command have currently two problems regarding tagging:

• without hyperref they are not tagged at all.
• \eqref is tagged as Lbl as it inherits tagging from the label in the equation.

The following resolves both (when hyperref it will replace the references with links, that is ok, but can be adjusted if needed)

\DocumentMetadata{uncompress,testphase={phase-III,math}}
\documentclass{article}
\usepackage{amsmath} 

\ExplSyntaxOn\makeatletter
\def\@kernel@target@exp#1{\cs_if_exist:cT
   {r@#1}{\tl_item:cn{r@#1}{4}}}

\NewSocket{tagsupport/ref/begin}{1}
\NewSocket{tagsupport/ref/end}{0}
\NewSocket{tagsupport/inlineinsert/begin}{1}
\NewSocket{tagsupport/inlineinsert/end}{0}

\NewSocketPlug{tagsupport/ref/begin}{kernel}
 {
  \leavevmode\tagmcend 
  \tagstructbegin{tag=Reference}
  \tag_struct_gput:nne 
   {\g__tag_struct_stack_current_tl}
   {ref_dest}{\@kernel@target@exp{#1}}
  \tagmcbegin{}
 }

\NewSocketPlug{tagsupport/ref/end}{kernel}
 {\tagmcend \tagstructend \tagmcbegin{}}

\AssignSocketPlug{tagsupport/ref/begin}{kernel} 
\AssignSocketPlug{tagsupport/ref/end}{kernel} 

\NewSocketPlug{tagsupport/inlineinsert/begin}{kernel}
  {\tagmcend \tagstructbegin{#1}\tagmcbegin{}}
\NewSocketPlug{tagsupport/inlineinsert/end}{kernel}
  {\tagmcend \tagstructend \tagmcbegin{}}

\AssignSocketPlug{tagsupport/inlineinsert/begin}{kernel} 
\AssignSocketPlug{tagsupport/inlineinsert/end}{kernel} 

\RenewDocumentCommand\ref{sm}
 {
  \UseTaggingSocket{ref/begin}{#2}
  \IfBooleanTF{#1}{\@kernel@sref{#2}}{\@kernel@ref{#2}}
  \UseTaggingSocket{ref/end}
 }

\DeclareRobustCommand{\eqref}[1]
  {
    \textup{%
    \AssignSocketPlug{tagsupport/inlineinsert/begin}{noop}%
    \AssignSocketPlug{tagsupport/inlineinsert/end}{noop}%  
    \tagform@{\ref{#1}}}
  }
\AtBeginDocument
 {
  \@namedef{maketag@@@}#1{%
    \ifmeasuring@
      \hbox{\m@th\normalfont#1}%
    \else
      \UseTaggingSocket{inlineinsert/begin}{tag=Lbl}%      
      \hbox{\m@th\normalfont#1}%
      \UseTaggingSocket{inlineinsert/end}%
    \fi
    } 
  }  
\ExplSyntaxOff\makeatother

\begin{document}

\section{section}\label{sec}

\ref{sec}
 
\begin{align}
x \label{eq}
\end{align}

\eqref{eq}
\end{document}