Altered marginpar conflicts with biblatex citation

Question

Consider the MWE below:

\documentclass[10pt,twoside,onecolumn,openright,draft]{memoir}
\usepackage{fontspec}
\usepackage{filecontents}
\usepackage{calc}
\usepackage[french]{babel}
\usepackage{mparhack}
\usepackage{csquotes}
\usepackage[authordate,strict,backend=biber,babel=other]{biblatex-chicago}

%\let\oldmarginpar\marginpar
%\renewcommand\marginpar[1]{\-\oldmarginpar[\raggedleft\footnotesize\hspace{0pt}#1]%
%{\raggedright\footnotesize\hspace{0pt}#1}}

\begin{filecontents}{references.bib}
@book{Thomsen:SL,
    author = {Thomsen, Marie-Louise},
title = {The Sumerian Language},
    subtitle = {An Introduction to its History and Grammatical Structure},
    shorttitle = {Sumerian Language},
    shorthand = {SL},
    edition = {2},
    series = {Mesopotamia Copehagen Studies in Assyriology},
    number = {10},
    location = {Copenhagen},
    publisher = {\foreignlanguage{danish}{Akademisk Forlag}},
    date = {1987},
    year = {1987}
}
\end{filecontents}
\bibliography{references.bib}

\begin{document}
Texte\marginpar{\cite[§228]{Thomsen:SL}} et encore.
\end{document}

This compiles fine. However, when I uncomment the redefinition of marginpar (which I've used successfully for a few years), I get

./minimal:33: Argument of \blx@citeargs@i has an extra }

Either the redefinition is problematic or else this causes a conflict of some kind with biblatex-chicago.

Any thoughts?

Answer 1

You hit a problem if there is ever a ] in the argument as then parsing for the optional argument goes wrong, so you need a {} group to hide the inner ]:

\let\oldmarginpar\marginpar
\renewcommand\marginpar[1]{\-\oldmarginpar[{\raggedleft\footnotesize\hspace{0pt}#1\par}]%
{\raggedright\footnotesize\hspace{0pt}#1}}