When traversing with a Lua filter in top-down mode, exclude Metadata fields from external YAML file

[kopeckyf]

With a Lua filter, I'm trying to traverse documents and an external YAML meta data file in topdown mode. My understanding is that metadata are accessible to Lua filters, but I thought that topdown traversal should make it possible to skip all meta data elements.

The head of the AST of my documet looks like this:

Pandoc
  Meta
    { unMeta =
        fromList
          [ ( "abstract"
            , MetaInlines
                [ Str "Recent"

However, adding the function

function Meta (n)
  return n, false
end

takes no effect. In other words, the filter is applied to children of Meta. That same function works fine for Cite or Link objects, which are then skipped by the filter.

Is it possible to exclude the entire Meta sub-tree from being processed by the filter?

[tarleb]

Indeed, looking at the code it seems that this is not implemented for Meta elements. Feel free to raise a bug.

My approach would be to place the filter in a table, and then use walk to apply the filter on the document body:

local my_filter = {
  traverse = 'topdown',
  Str = function (s)
    -- ...
  end
}

function Pandoc(doc)
  doc.blocks = doc.blocks:walk(my_filter)
  return doc
end

[kopeckyf]

Nice idea, thank you! Will be opening an issue later

[kopeckyf]

Issue number for future reference: #9381