Building meta array in Lua to iterate in template

[lifeunleaded]

I'm using an adaptation of @tarleb 's abstract-section to build a table (array) of sections in Meta in a Lua filter, to iterate over in a template. Below is part of the filter that puts a section inside a nested array in Meta named sections. The reason is that I'd like to iterate over sections in the template.

  meta['sections'] = {}
  for metakey in pairs(section_identifiers) do
    metakey = stringify(metakey)
    local section = collected[metakey]
    if not meta[metakey] and section and #section > 0 then
      meta['sections'][metakey] = pandoc.MetaBlocks(section)
    end
  end

When I try to access it in the template, I can access things in sections directly by knowing their index (the identifier), but not iterate over them with $for$.

A test template with these (using docbook output to test):

<remark>sections loop</remark>
$for(sections)$
  $sections$
$endfor$
<remark>sections</remark>
$sections$
<remark>sections.myheading</remark>
$sections.myheading$

Gives me this:

<remark>sections loop</remark>
  true
<remark>sections</remark>
true
<remark>sections.myheading</remark>
[correct expected content for myheading, an item in sections] 

How should I form the sections table in Lua to be able to iterate over it in the template?

[lifeunleaded]

Having written the question, I realized the answer: index the table as a 1-indexed array, not with arbitrary identifiers.

meta['sections'] = {}
  i = 1
  for metakey in pairs(section_identifiers) do
    print('metakey', metakey)
    metakey = stringify(metakey)
    local section = collected[metakey]
    if section and #section > 0 then
      meta['sections'][i] = pandoc.MetaBlocks(section)
      i = i + 1
    end
  end

This gives me correct results when using $for$ in the template.

[tarleb]

Alternatively, using sections/pairs should work, too. See https://pandoc.org/MANUAL#pipes.