[Tex/LaTex] Put square brackets around custom item labels

Question

I want to put a set of square brackets only around custom item labels.
The default labels should remain unchanged.

See the following code:

\documentclass{article}

\begin{document}

\begin{itemize}
\item First
\item [12] Second
\item Third
\end{itemize}

\begin{itemize}
\item First
\item [[12]] Second
\item Third
\end{itemize}


\end{document}

In the first list, the item label 12 appears bare. I want it to appear
as [12]. In the second list, if the custom label is put with an
extra of pair of brackets, the effect is almost achieved but we get a redundant space before the right bracket.

The ideal solution would be a global one, may be putting some command
or key value along with \begin{itemize}, which would not require the
forced extra pair as in the second list.

(I was under the impression that enumitem would be my savior, but somehow I failed to locate the solution.)

Answer 1

Your example solved:

\documentclass{article}
\begin{document}
    \begin{itemize}
        \item First
        \item [{[12]}] Second
    \end{itemize}
\end{document}

And for automatisation I would define a new command that would than apply the brackets like that. (But there may be a more elegant way to integrate it in the default \item command.)

\documentclass{article}
\newcommand\citem[1]{\item[{[#1]}] }
\begin{document}
    \begin{itemize}
        \item First
        \citem{12} Second
    \end{itemize}
\end{document}

The result in both cases: