marked-up index entries fail with hyperref

[kberry]

An index entry with added markup, plus hyperref being used, is misparsed by xindy. Originally discovered by Alexander Krumeich.

Before Juergen's changes in May 2020 to support hyperindexformat cross-reference-class, such entries were completely omitted from the .ind (e.g., in TL2020-original). With the changes (e.g., in TL 2021 and TL2020-final), the entries are a mishmash with the markup command.

Example file below (named, arbitrarily, ih.tex) that makes two index entries: a "defining" one (markup with \textbf), and a normal one. The defining one gets messed up in the ind. Originally from Alexander; I cut it down to use only the basic {makeidx} package and added comments about the various cases.

\listfiles
\documentclass{article}

\usepackage{makeidx}\makeindex
\usepackage{hyperref}

% with hyperref enabled, and using current texindy ih.idx,
% the .ind is broken, containing (missing the page number 1):
%   \item example, \hyperpage{2}, \hyperindexformat{\textbf}{}

% until the 2020-05-28 changes from spitz, get:
%   WARNING: unknown cross-reference-class `hyperindexformat'! (ignored)
% and the page 1 ("defining") entry is missing:
%   \item example, \hyperpage{2}

% if comment out hyperref, using texindy, the .ind is fine, containing:
%   \item example, \textbf{1}, 2

% if leave hyperref enabled, and use makeindex, the .ind is also ok:
%   \item example, \hyperpage{2}
%   \item example, \hyperindexformat{\textbf}{1}

\newcommand{\definingindexentry}[1]{\index{#1@#1|textbf}#1}

\begin{document}
First page, a defining \definingindexentry{example}.

% If comment out the marked-up index entry and just have regular
% entries, all cases are fine (not surprisingly):
%First page, a defining \index{example}.

\clearpage{}
Second page, a normal \index{example}.
\printindex

\end{document}

Just for possible convenience, the ChangeLog entry for Juergen's changes which I installed last year, with more references:

2020-05-28  J\"urgen Spitzm\"uller  <spitz@lyx.org>

        These patches from:
        https://tug.org/pipermail/tex-live/2020-May/045760.html

        * xindy-src/src/markup.lsp: support giving attributes to the
        markup of separator with :attr.
        * doc/manual-3.html: document this.
        https://sourceforge.net/p/xindy/bugs/1/

        * xindy-src/modules/base/makeindex.xdy
        (define-crossref-class, markup-crossref-list): handle
        \see and \seealso added by hyperref.
        * xindy-src/user-commands/texindy.in,
        * xindy-src/user-commands/xindy.in: corresponding doc updates.
        https://sourceforge.net/p/xindy/bugs/62/

        * xindy-src/doc/faq-4.html,
        * xindy-src/doc/manual-3.html: document workaround for
        :min-range-length none being broken.
        https://github.com/jschrod/xindy.ctan/issues/3

[jspitz]

Alas I think fixing this requires fundamental changes in xindy (beyond my lisp abilities). The problem is that we do not seem to have a way to handle the page number as a second argument and thus close with an empty second argument. This is also the reason why \seealso does not work properly in xindy (it's just an alias for \see).

[kberry]

Fair enough. Thanks for looking at it, J\"urgen.

I guess it will have to await Joachim's copious spare time to ever be fixed. It's not something I'm going to tackle. --best, karl.