How to get \hypereff[]{} working with htlatex?

Question

In this minimal example:

\documentclass[11pt]{book}
\usepackage[utf8]{inputenc}
\usepackage[]{hyperref}

\begin{document}
Hahaha \hyperref[other]{2}
\end{document}

Compiling with pdflatex, it ends up fine:

However when I compile it with

make4ht minimal.tex "mathml"

The html version does not show the number correctly.

I would like to know, how can I adjust htlatex so that it correctly produces documents with \hyperref?

Thanks

Answer 1

It seems like a bug in TeX4ht support for the \hyperref command. It uses the \ref command internally, so when the linked label is not found, it will print ?? to signalize the missing reference. As you don't have any other label in your document, you get this missing reference sign.

You can use the following config file to mimic the \hyperref behavior, which prints the text even when reference is missing:

\Preamble{xhtml}
\makeatletter
\def\label@hyperref[#1]{%
  \expandafter\label@@hyperref\csname r@#1\endcsname{#1}%
}%
\def\label@@hyperref#1#2#3{%
  \ifx#1\relax
    \protect\G@refundefinedtrue
    \@latex@warning{%
      Hyper reference `#2' on page \thepage \space undefined%
    }%
    \begingroup
      \hyperrefundefinedlink{#3}%
    \endgroup
  \else%
    \def\hyperrefLabel{#3}%
    \Configure{ref}%
      {\Link}{\EndLink}{\Configure{ref}{}{}{}#3}\ref{#2}%
  \fi
}
\makeatother
\begin{document}
\EndPreamble

compile using:

 make4ht -c config.cfg minimal.tex "mathml"

This is the result: