Is it possible in some way to pass a file path as argument to pandoc.read() in Lua filters or do you have to first get a string using Lua's io.open() and file:read()? If no would it maybe be a good idea to allow passing a table `{ file = 'path/to/file'}` instead of a string to read from a file? This is assuming that the problems I am having opening files with Lua from inside filters (I think the files are not found) may not be present from Haskell.
Also is there some way to read a YAML file into a (meta)data structure without manually making sure that the string starts/ends with `---\n`/`\n...\n`? Using `yaml = yaml:gsub('^%s*%-%-%-%%s*', ''):gsub('^', '---\n')` and its EOS counterpart is a rather blunt method.