Option "label" adds an extra pair of braces to \cs{the\@enumctr}

[muzimuzhi]

When option label is used, an extra pair of braces is added to \cs{the\@enumctr}, which influences \@currentlabel. This may break macros aiming to retrieve value from a label, for example the \gerrefnumber from refcount package (see this TeX-SX question as an example).

Is this pair of braces a must?

\documentclass{article}
\usepackage{enumitem}

\begin{document}
\makeatletter
\def\test{\meaning\@currentlabel}
\makeatother

\begin{enumerate}
  \item text \test
  % this defines \@currentlabel to "1"
\end{enumerate}

\begin{enumerate}[label=\arabic*., ref=\arabic*]
  \item text \test
  % this defines \@currentlabel to "{1}"
\end{enumerate}
\end{document}

Related source code, see line 548:

enumitem/enumitem.sty

Lines 541 to 551 in 1bdcad0

	\def\enit@reflabel#1#2{%
	\ifnum\enit@depth=\@ne\else % no level 0
	\advance\enit@depth\@ne
	\@namedef{p@\@enumctr}{}% Don't accumulate labels
	\advance\enit@depth\m@ne
	\fi
	\ifcase#2%
	\@namedef{the\@enumctr}{{#1}}%
	\else
	\enit@normlabel{\csname the\@enumctr\endcsname}{#1}%
	\fi}

[jbezos]

Braces are necessary because the label can contain formatting macros and \ref is in the global (or rather, non-local) scope. I can't think of any simple solution.

[muzimuzhi]

Just found that if only the label option is used, then two pairs of braces are added.

\documentclass{article}
\usepackage{enumitem}

\begin{document}
\makeatletter
\def\test{\texttt{\meaning\@currentlabel}}
\makeatother

\begin{enumerate}
  \item text \test
  % this defines \@currentlabel to "1"
\end{enumerate}

\begin{enumerate}[label=\arabic*.]
  \item text \test
  % this defines \@currentlabel to "{{1.}}"
\end{enumerate}

\begin{enumerate}[ref=\arabic*]
  \item text \test
  % this defines \@currentlabel to "{1}"
\end{enumerate}
\end{document}

Concerning formatting macros, I think it's users responsibility to make the scope local. After all users are free to redefine each of the \the<counter> and \p@<counter> (or by using \labelformat in recent LaTeX releases).

But for backwards-compatibility concerns, I understand that enumitem may want to keep the current behavior of label and ref options, and only provide new possibilities through new options.