Exsheets does not work with unicode-math package

Question

Here is the code:

\documentclass{article}
\usepackage[vmargin=1in]{geometry}
\usepackage{xfrac,fontspec,unicode-math}
\setmathfont[version=lm]{Latin Modern Math}
\setmathfont[version=cambria]{Cambria Math}
\usepackage{xgreek}
\usepackage{exsheets}
\begin{document}

\setmainfont{Latin Modern Roman}
\mathversion{lm}
\section*{Latin Modern}
There follows a question
\begin{question}
This is the first question
\end{question}\\
\begin{question}[name=Problem]
This is the second question
\end{question}


\setmainfont{Cambria}
\mathversion{cambria}
\section*{Cambria, Cambria Math}
There follows a question 
\begin{question}
This is the first question
\end{question}\\
\begin{question}[name=Problem]
This is the second question
\end{question}
\end{document}

and the output is

Does anybody has a solution?

*Exsheets works fine with xelatex if unicode-math is not in the preamble

Answer 1

This is a known issue. The file unicode-math-table.tex that is loaded by unicode-math contains the following line:

\UnicodeMathSymbol{"0003F}{\question}{\mathord}{question mark}%

This means that at begin document \question gets defined or redefined (unicode-math does \AtBeginDocument{\um_define_math_chars:} which supposedly initiates the definition...) The file

\documentclass{article}
\usepackage{unicode-math}
\show\question
\begin{document}
\show\question
\end{document}

produces in the log

> \question=undefined.
l.3 \show\question

and

> \question=the character ?.
l.5 \show\question

And the character ? is exactly what you're seeing when you use exsheets' \begin{question}. (Remember that \begin{foo} amongst other things calls the command \foo.)

There are two solutions for this:

1. redefine \question again at begin document by adding

   \AtBeginDocument{\RenewQuSolPair{question}{solution}}
   

   after loading both unicode-math and exsheets. You'll lose unicode-math's \question then.

2. Use another exercise environment by defining a new one, e.g.,

   \NewQuSolPair{exercise}{answer}
   

Here's an example for the first version:

\documentclass{article}
\usepackage{unicode-math}
\usepackage{exsheets}
\AtBeginDocument{\RenewQuSolPair{question}{solution}}
\begin{document}
\begin{question}
  This is a question.
\end{question}
\begin{solution}[print]
  This is a solution.
\end{solution}
\end{document}

Here's an example for the second possibility:

\documentclass{article}
\usepackage{unicode-math}
\usepackage{exsheets}
\NewQuSolPair{exercise}{answer}
\begin{document}
\begin{exercise}
  This is a question.
\end{exercise}
\begin{answer}[print]
  This is a solution.
\end{answer}
\end{document}

Both give