通过pandoc lua过滤器添加元数据字段

Question

I'm processing a markdown document such as

---
title: "dummy title"
highlight: "c"
highlighted: 'highlighted'
---     
body text

into a highly-customised latex template where, among other things "c" is being highlighted as part of a larger tex macro. One last step is resisting me: the dummy metadata "highlighted" should not have to be specified here, but I can't find a way to generate it in the lua filter below:

text = require 'text'
newstring = '\\textit{a,b,c,d}'

function meta_vars (m)
       -- m.highlighted = 'highlighted' -- not working
        highlight = m.highlight
  return m
end

function replace (elem)
      if elem.text == 'highlighted' then
        newstring = newstring:gsub(pandoc.utils.stringify(highlight),
                       '{\\bfseries '..pandoc.utils.stringify(highlight)..'}')
        return pandoc.RawInline("latex", newstring)
        else
        return elem
      end
    end

return {{Meta = meta_vars}, {Str = replace}}

with the following custom template

\documentclass[12pt]{article}

\begin{document}

\title{$title$ -- $highlighted$}
\maketitle
$body$
\end{document}

The command to run this example is

pandoc +RTS -K512m -RTS test.utf8.md --to latex --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash --output test.tex --template _tpl.tex --lua-filter=filter.lua 

producing, as advertised

enter image description here

How can I get rid off the dummy highlighted tag in my YAML header?

Answer 1

I don't really understand exactly what you're doing with the latex macros here, but the crux of your question seems to be about adding a new metadata element. The line that you have commented out with --not working seems to work fine for me. You might want to explicitly set the type with

m.highlighted=pandoc.MetaString('highlighted')

but I don't think that will change anything.

I also note that as it is written the newstring variable will be modified whenever the word highlighted appears in the text. With two lines of highlighted the newstring will equal \\textit{a,b,{\\bfseries {\\bfseries c}},d} .

Perhaps you could restate your question with the latex macro stuff removed and just focus on what you want the filter to do.