RSC-005 [EPUB3 Error Code] if \caption before \includegraphics

[Kuan-Lun]

The following is an example. I use tex4ebook --format epub3 "main.tex".

% main.tex
\documentclass{article}
\usepackage{graphicx}
\title{Test}
\author{Test}
\date{2023-08-12}
\begin{document}
\maketitle
\tableofcontents
\begin{figure}
\caption{123}
\includegraphics{test.png}
\end{figure}
%%%% The following is fine.
% \begin{figure}
% \includegraphics{test.png}
% \caption{123}
% \end{figure}
\end{document}

The mainli1.xhtml in the output file main.epub is incorrect by EPUBCheck.

Validating using EPUB version 3.2 rules.
ERROR(RSC-005): [path]/main.epub/OEBPS/mainli1.xhtml(19,33): Error while parsing file: element "img" not allowed here; expected the element end-tag

Check finished with errors
Messages: 0 fatals / 1 error / 0 warnings / 0 infos

EPUBCheck completed

[michal-h21]

It should be fixed in the development version of make4ht. Until it is available in TeX Live (I am not sure when I will release the new version), you can use this build file:

local domfilter = require "make4ht-domfilter"

local process = domfilter {
  function(dom)
    for _, el in ipairs(dom:query_selector("figure > a")) do
      local id = el:get_attribute "id" 
      if id then
        local parent = el:get_parent()
        if not parent:get_attribute("id") then
          parent:set_attribute("id", id)
          el:remove_node()
        end
      end
    end
    return dom
  end
}

Make:match("html$", process)

Compile using

$ tex4ebook -e build.lua --format epub3 "main.tex".