List indentation is fragile in ConTeXt

[andreiborisov]

Missing one space symbol in item indentation causes compilation to fail. Here is an example:

- First element
- Second element
   #. First subelement
    #. Second subelement
- Third element

That transforms to:

\markdownRendererUlBeginTight
\markdownRendererUlItem First element\markdownRendererUlItemEnd 
\markdownRendererUlItem Second element #. First subelement\markdownRendererInterblockSeparator
{}\markdownRendererOlBeginTight
\markdownRendererOlItem Second subelement\markdownRendererOlItemEnd 
\markdownRendererOlEndTight \markdownRendererUlItemEnd 
\markdownRendererUlItem Third element\markdownRendererUlItemEnd 
\markdownRendererUlEndTight \relax

Which fails to compile:

You can't use 'parameter character U+0023 'hash tag'' in horizontal mode

<line 11.3> 
    \markdownRendererUlItem Second element #
    . First subelement\markdownRendererInterblockSeparator

1     \markdownRendererUlBeginTight
2     \markdownRendererUlItem First element\markdownRendererUlItemEnd 
3 >>  \markdownRendererUlItem Second element #. First subelement\markdownRendererInterblockSeparator
4     {}\markdownRendererOlBeginTight
5     \markdownRendererOlItem Second subelement\markdownRendererOlItemEnd 
6     \markdownRendererOlEndTight \markdownRendererUlItemEnd 
7     \markdownRendererUlItem Third element\markdownRendererUlItemEnd 
8     \markdownRendererUlEndTight \relax

[Witiko]

In the ConTeXt module (as well as in the plain TeX and LaTeX modules and in the OpTeX example), we change the catcodes of characters % and # to category 12 (other) before we input the transformed document:

markdown/markdown.dtx

Lines 31555 to 31572 in 6918a31

	|gdef|markdownInput#1{%
	% \end{macrocode}
	% \begin{markdown}
	% Change the category code of the percent sign (`\%`) to other, so that a user
	% of the \Opt{hybrid} Lua option or a malevolent actor can't produce TeX
	% comments in the plain TeX output of the Markdown package.
	% \end{markdown}
	% \begin{macrocode}
	|begingroup
	|catcode`|%=12
	% \end{macrocode}
	% \begin{markdown}
	% Furthermore, also change the category code of the hash sign (`#`) to other,
	% so that it's safe to tokenize the plain TeX output without mistaking hash
	% signs with TeX's parameter numbers.
	% \end{markdown}
	% \begin{macrocode}
	|catcode`|#=12

This causes # to be typeset as a hash sign.

You should set the catcodes before manually inputting the transformed document as follows:

\begingroup
\catcode`\%=12
\catcode`\#=12
Here goes the transformed document.
\endgroup

I can see that this is not properly documented in the user manual:

• Sections 1.3.1 Using Lua and 2.1.1.1 Lua Module make no mention of this.
• Section 2.1.1.2 Lua Command-Line Interface only mentions the percent sign.
• Throughout Section 2.2 Options, none of the unnumbered subsections Lua Module Example and Lua CLI Example make a mention of this with the exception of Section 2.2.1.31 Option hybrid, where the unnumberes subsection Lua CLI Example mentions the percent sign.

This will need fixing before the 3.0.0 release. Thanks for the report.

@andreiborisov, did you notice any other place in the documentation, where this should be stressed?