It works wonderfully. I made some minor modifications to allow it to work more like a `citefield` filter in general, and to avoid an error due to invalid field names passed as args. I think we could call it ready unless anyone else has suggestions. For fields with names such as authors, editors and translators, it seemed enough to get the family name of the first name, but other could prefer it to behave differently, of course.


```
local function get_keys(t)
  local keys={}
  for key,_ in pairs(t) do
    table.insert(keys, key)
  end
  return keys
end

stringify = require 'pandoc.utils'.stringify

function Pandoc (doc)
  doc.meta.references = pandoc.utils.references(doc)
  doc.meta.bibliography = nil
  return doc:walk{
    Span = function (span)
      -- check that the span contains only a single cite object
      local cite = span.content[1]
      local citations = cite and cite.citations or nil
      if #span.content == 1 and cite.t == 'Cite' and #citations == 1 then
        local cite_id = citations[1].id
        local ref = doc.meta.references:find_if(
          function (r) return cite_id == r.id end
        )
        local the_arg = span.classes[1]
        local the_result = ""
        if ref and the_arg then
          if string.find(stringify(get_keys(ref)), the_arg) then
          -- replace the span with a specific citation field
            if the_arg == "author" or the_arg == "editor" or the_arg == "translator" then
              the_result = stringify(ref[the_arg][1]["family"])
            else if the_arg == "title" then
                the_result = pandoc.Emph{stringify(ref[the_arg])}
              else
                the_result = stringify(ref[the_arg])
              end
            end
          else
          -- return the span unchanged
          the_result = span
          end
          return the_result
        end
      end
    end
  }
end
```

Um abraço,
Bernardo

From: pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org <pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> on behalf of Bernardo C. D. A. Vasconcelos <bernardovasconcelos-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Date: Thursday, 9 March 2023 11:37
To: pandoc-discuss <pandoc-discuss-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>
Subject: Re: Lua Filter for citeauthor and citetitle in HTML
Albert,
that is vexingly short, but the syntax is perfectly clear. Thank you! Since I toiled at this for a while, your filter will provide me with some interesting learning opportunities. I will play around with it and see how it behaves with the other Lua filters.
Thanks again,
B.

On Thursday, March 9, 2023 at 9:44:30 AM UTC-3 Albert Krewinkel wrote:

"Bernardo C. D. A. Vasconcelos" <bernardov...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> A filter that seems close enough is the bibexport filter at https://
> raw.githubusercontent.com/pandoc/lua-filters/master/bibexport/<http://raw.githubusercontent.com/pandoc/lua-filters/master/bibexport/>
> bibexport.lua which I reproduce below:

Newer pandoc versions allow to shorten this to

```
function Pandoc (doc)
doc.meta.references = pandoc.utils.references(doc)
doc.meta.bibliography = nil
return doc
end
```

Here's a "quick n' dirty" filter that should make your `[@key]{.title}`
syntax work:

```
function Pandoc (doc)
doc.meta.references = pandoc.utils.references(doc)
doc.meta.bibliography = nil
return doc:walk{
Span = function (span)
-- check that the span contains only a single cite object
local cite = span.content[1]
local citations = cite and cite.citations or nil
if #span.content == 1 and cite.t == 'Cite' and #citations == 1 then
local cite_id = citations[1].id
local ref = doc.meta.references:find_if(
function (r) return cite_id == r.id<http://r.id> end
)
if ref and span.classes[1] then
-- replace the span with a specific citation field
return ref[span.classes[1]]
end
end
end
}
end
```

It's a bit condensed and not well documented, so let me know if you have
questions.


--
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe e836 388d c0b2 1f63 1124
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