pandoc filter in lua and walk_block

问题

I'm trying to apply a LUA filter that would only alter the body of a document, leaving the Metadata untouched. And it's harder than I thought.

The filter should prepend and append text to inline elements as well as block elements. If it works for the inline element, here Code, it fails for the block element CodeBlock.

function Pandoc(doc)
  blocks = {}
  for k,block in pairs(doc.blocks) do
    table.insert(blocks, pandoc.walk_block(block, {
      -- Doesn't work!?
      CodeBlock = function(el)
        return {
          pandoc.Para({pandoc.Str("Before")}),
          el,
          pandoc.Para({pandoc.Str("After")})}
      end,
      -- Works!
      Code = function(el)
        return {pandoc.Str("Before"), el, pandoc.Str("After")}
      end,
    }))
  end

  return pandoc.Pandoc(blocks, doc.meta)
end

What am I missing? Cheers,

回答1:

The issue here is that walk_block and walk_inline process the content of an element, not the element itself.

If wrapper is your filter table, this should do what you want:

function Pandoc (doc)
  local div = pandoc.Div(doc.blocks)
  local blocks = pandoc.walk_block(div, wrapper).content
  return pandoc.Pandoc(blocks, doc.meta)
end

An alternative solution would be to save and restore the metadata, like so:

local meta = {}
return {
  { Meta = function(m) meta = m; return {} end },
  wrapper,
  { Meta = function(_) return meta; end },
}

This is probably more efficient, as serializing/deserializing only metadata and Code/CodeBlock elements is likely faster than doing the same for the full document.

来源：https://stackoverflow.com/questions/47350104/pandoc-filter-in-lua-and-walk-block

标签

lua

pandoc