[tex4ht] [bug #557] tex4ht no longer process some math. What is the cause?

Thu Mar 24 22:20:55 CET 2022

URL:
  <http://puszcza.gnu.org.ua/bugs/?557>

                 Summary: tex4ht no longer process some math. What is the
cause?
                 Project: tex4ht
            Submitted by: nma123
            Submitted on: Thu Mar 24 21:20:55 2022
                Category: None
                Priority: 5 - Normal
                Severity: 7 - Important
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

    _______________________________________________________

Details:

reference and screen shots at

https://tex.stackexchange.com/questions/638304/tex4ht-no-longer-process-some-math-what-is-the-cause

This looks like a new serious problem.

I have a document that used to compile OK with tex4ht. I have not build it for
someone. Today when I build it to HTML it is not able to convert some math to
HTML.

This only happens when using mathjax mode. The math is all valid amsmath
package math so One would expect mathjax to handle it directly.

Here is MWE
=====================
\documentclass[12pt]{book}
\usepackage{amsmath}
\begin{document}
\begin{align}%
\begin{Bmatrix}
c_{1}\\
c_{2}\\
c_{3}\\
c_{4}%
\end{Bmatrix}
&  =%
\begin{pmatrix}
1 & -a & -b & ab\\
1 & a & -b & -ab\\
1 & a & b & ab\\
1 & -a & b & ab
\end{pmatrix}
^{-1}\tag{2}%
\end{align}
\end{document}
====================
And now 

 make4ht  -ulm default -a debug foo2.tex "mathjax,htm" 

gives HTML error (screen shot)

tex4ht compiles it OK when removing mathjax options, which indicates mathjax
is either not able to handle this correctly or tex4ht generated wrong HTML?
But then how did it work OK before?

Here is the raw HTML

==================
<!DOCTYPE html> 
<html lang='en-US' xml:lang='en-US'> 
<head><title></title> 
<meta charset='utf-8' /> 
<meta content='TeX4ht (https://tug.org/tex4ht/)' name='generator' /> 
<meta content='width=device-width,initial-scale=1' name='viewport' /> 
<link href='foo2.css' rel='stylesheet' type='text/css' /> 
<meta content='foo2.tex' name='src' /> 
<script>window.MathJax = { tex: { tags: "ams", }, }; </script> 
 <script async='async' id='MathJax-script'
src='https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js'
type='text/javascript'></script>  
</head><body>
<!-- l. 33 --><p class='noindent'>\begin {align} \csname
@begin:Bmatrix\endcsname \choose:begin {\let \choose:begin \@firstoftwo \ifx
\EndPicture \:Undef \PushStack \envn:list \n:list \SaveEverypar \fi \let
\chk:pic \EndPicture \ifx \EndPicture \:UnDef \list:save \let \after:end
\empty \csname before:beginBmatrix\endcsname \fi \UseHook
{env/Bmatrix/before}\@ifundefined {Bmatrix}{\def \reserved at a {\@latex at error
{Environment Bmatrix undefined}\@eha }}{\def \reserved at a {\def \@currenvir
{Bmatrix}\edef \@currenvline {\on at line }\ifx \EndPicture \:UnDef \ifx
\this:listConfigure \empty \null:listConfigure \csname
onBmatrix:list\endcsname \fi \fi \@execute at begin@hook {Bmatrix}\csname
Bmatrix\endcsname }}\global \@ignorefalse \begingroup \@endpefalse \reserved at a
}{\o:begin: {Bmatrix}} c_{1}\\ c_{2}\\ c_{3}\\ c_{4}\end {Bmatrix} &
=\begin {pmatrix} 1 & -a & -b & ab\\ 1 & a & -b &
-ab\\ 1 & a & b & ab\\ 1 & -a & b & ab \end {pmatrix}
^{-1}\tag {2} \end {align}
</p>   

</body> 
</html>
===================

What has changed to cause this math no longer to work in mathjax mode of
tex4ht?

Using TL 2021, fully updated about 2 week ago. On Linux ubuntu.

Thanks
--Nasser

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