Add short toc entry to toc entry and vice versa

Question

Taking heavy inspiration from the answer to:

Hide toc from toc, and shorttoc from shorttoc

I have made the following code:

\documentclass{memoir}

\newcommand{\shorttoc}{%
\renewcommand*{\contentsname}{Short Contents}
\begingroup%
\def\inshorttoc{}%
\tableofcontents*%
\addtocontents{toc}{\string\ifdefined\string\inshorttoc\string\else}%
\addcontentsline{toc}{chapter}{\contentsname}%
\addtocontents{toc}{\string\fi}%
\endgroup%
}

\newcommand{\toc}{%
\renewcommand*{\contentsname}{Contents}
\begingroup%
\def\intoc{}
\tableofcontents*
\addtocontents{toc}{\string\ifdefined\string\intoc\string\else}%
\addcontentsline{toc}{chapter}{\contentsname}%
\addtocontents{toc}{\string\fi}%
\endgroup%
}
\makeatother

\usepackage{mwe}

\begin{document}
\shorttoc

\cleardoublepage

\toc

\blinddocument
\end{document}

It should place the short contents entry into the long toc and vice versa. But after updating my TeX live distribution the code throws the errors:

Extra }, or forgotten \endgroup. \@writefile{toc}{\fi}
Extra }, or forgotten \endgroup. \@writefile{toc}{\fi}

But the code compiles without errors on older distributions.

Answer 1

Looking into the newer releases of LaTeX I found out that the @\writefile command has been changed slightly (see pages 269--271 in the 2018-12-01 version of the LaTeX2e source documentation, a link is https://www.latex-project.org/help/documentation/source2e.pdf) to solve some problems with spurious spaces. Using the old definition of the @writefile command solved the problem, it is:

\long\def\@writefile#1#2{%
  \@ifundefined{tf@#1}\relax
    {\@temptokena{#2}%
     \immediate\write\csname tf@#1\endcsname{\the\@temptokena}%
    }%
}

A proper solution would avoid this redefinition of @writefile.