Custom clever ref and and short captions giving error

Question

I have been using the following modification of \Cref in my document to provide names to theorems and lemmas if one is given (as I think it reads nicer). As in the MWE (based on this answer to a previous question).

However, I just noticed that when I have a custom command in the short caption field I get the following error: Incomplete \iffalse; all text was ignored after line 68. I have commented this line out so it compiles for now, but I have several of these scattered throughout many short captions. Is there a fix?

MWE

(\caption[\oliver's short caption]{\oliver's figure} causes the issues.)

\documentclass[a4paper,10pt]{extarticle}


\usepackage{amsmath,mathtools,graphicx,etoolbox,nameref,amsthm,cleveref,xspace}
% Have theorems and lemmas be referenced by name if applicable.
\makeatletter
\renewrobustcmd{\cref}{\@osmcref{cref}}
\renewrobustcmd{\Cref}{\@osmcref{Cref}}
\def\@osmcref#1#2{%
    \begingroup
    \ifcsundef{r@#2}
    {}
    {\edef\@osmcref@name{%
            \expandafter\expandafter\expandafter
            \@thirdoffive\csname r@#2\endcsname}}%
    \ifcsundef{r@#2@cref}
    {}
    {\cref@gettype{#2}{\@osmcref@type}}%
    \ifboolexpr{not test {\ifdefvoid{\@osmcref@name}}
        and (test {\ifdefstring{\@osmcref@type}{theorem}}
        or test {\ifdefstring{\@osmcref@type}{lemma}})}
    {\nameref{#2} (\@cref{#1}{#2})}
    {\@cref{#1}{#2}}%
    \endgroup
}
\makeatother
% Give bold names to definitions and similar environments. 
\makeatletter
\def\th@plain{%
    \thm@notefont{}% same as heading font
    \itshape % body font
}
\def\th@definition{%
    \thm@notefont{}% same as heading font
    \normalfont % body font
}
\makeatother
% Giving correct theorem and lemma environments. 
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}
% Naming these nicely.
\crefname{lemma}{lemma}{lemmas}
\Crefname{lemma}{Lemma}{Lemmas}
\crefname{theorem}{theorem}{theorems}
\Crefname{theorem}{Theorem}{Theorems}


\newcommand{\oliver}{Oliver\xspace}


\begin{document}
    \section{Commands and short captions}
    \label{sec}

    \begin{lemma}\label{noname}
        Extremely important lemma that has no name.
    \end{lemma}

    \begin{lemma}[Fatou's lemma]\label{boringLemma}
        This is some boring statement.
    \end{lemma}

    \begin{theorem}[Fubini's Theorem]\label{awesomeTheorem}
        This is a really awesome statement.
    \end{theorem}

    \Cref{fig} Doesn't work when I have \verb|\oliver| in the short caption. 

    \begin{figure}[htb]
        \centering
        Something interesting.
        \caption[Oliver's short caption]{\oliver's figure}
%        \caption[\oliver's short caption]{\oliver's figure} % The troublesome line.
        \label{fig}
    \end{figure}

    We have \Cref{boringLemma} and \Cref{awesomeTheorem}. Whereas \Cref{noname} doesn't have anything interesting.


\end{document}

Answer 1

The unprotected \edef was a bit too eager. Try

\makeatletter
\newcommand\expandthrice{%
  \unexpanded\expandafter\expandafter\expandafter
  \expandafter\expandafter\expandafter\expandafter}
\renewrobustcmd{\cref}{\@osmcref{cref}}
\renewrobustcmd{\Cref}{\@osmcref{Cref}}
\def\@osmcref#1#2{%
  \begingroup
    \ifcsundef{r@#2}
      {}
      {\edef\@osmcref@name{\expandthrice{%
         \expandafter\expandafter\expandafter
         \@thirdoffive\csname r@#2\endcsname}}}%
    \ifcsundef{r@#2@cref}
      {}
      {\cref@gettype{#2}{\@osmcref@type}}%
    \ifboolexpr{not test {\ifdefvoid{\@osmcref@name}}
                and (test {\ifdefstring{\@osmcref@type}{thm}}
                     or test {\ifdefstring{\@osmcref@type}{lemma}})}
      {\nameref{#2} (\@cref{#1}{#2})}
      {\@cref{#1}{#2}}%
    \endgroup
}
\makeatother

or this beauty

\makeatletter
\renewrobustcmd{\cref}{\@osmcref{cref}}
\renewrobustcmd{\Cref}{\@osmcref{Cref}}
\def\@osmcref#1#2{%
  \begingroup
    \ifcsundef{r@#2}
      {}
      {\expandafter\expandafter\expandafter\expandafter\expandafter
         \expandafter\expandafter\def
       \expandafter\expandafter\expandafter\expandafter\expandafter
         \expandafter\expandafter\@osmcref@name
       \expandafter\expandafter\expandafter\expandafter\expandafter
         \expandafter\expandafter{%
         \expandafter\expandafter\expandafter
         \@thirdoffive\csname r@#2\endcsname}}%
    \ifcsundef{r@#2@cref}
      {}
      {\cref@gettype{#2}{\@osmcref@type}}%
    \ifboolexpr{not test {\ifdefvoid{\@osmcref@name}}
                and (test {\ifdefstring{\@osmcref@type}{thm}}
                     or test {\ifdefstring{\@osmcref@type}{lemma}})}
      {\nameref{#2} (\@cref{#1}{#2})}
      {\@cref{#1}{#2}}%
    \endgroup
}
\makeatother

instead.

I have updated my answer to Clever Ref to only give theorem names. with the seven \expandafters monster.

The first solution with \expandthrice expands the contents of \@osmcref@name three times by placing it in an \edef (which normally tries to expand as far as possible) but stopping the expansion after three steps with \expandthrice (essentially this is etoolbox's \expandonce but for three expansion steps). The second solution with the seven \expandafters immediately only expands the contents of \@osmcref@name three times before saving. I somehow feel that the second solution is a bit nicer because it does not define a new command and because it performs the necessary expansion steps explicitly, whereas the first solution stops an explicit full expansion in the right place.