Pandoc Lua filter to replace specific English words to Chinese words in citations

Question

When writing a Chinese paper, both Chinese and English papers could be cited. However, styles are slightly differently. The example is as follows:

Cite an English article (Smith et al. 2022), and cite a Chinese article (张三 等 2018).

In other words, for papers with multiple authors, et al. is used for English papers, while 等 is applied for Chinese papers. Considering that Citation Style Language cannot handle multiple languages, I’d ask help for Lua filter.

A Markdown file named test.md as an example:

Cite an English article [@makarchev2022], and cite a Chinese article [@luohongyun2018].

Then run the command below:

pandoc -C -t native test.md

And the output of the main body:

[ Para
    [ Str "Cite"
    , Space
    , Str "an"
    , Space
    , Str "English"
    , Space
    , Str "article"
    , Space
    , Cite
        [ Citation
            { citationId = "makarchev2022"
            , citationPrefix = []
            , citationSuffix = []
            , citationMode = NormalCitation
            , citationNoteNum = 1
            , citationHash = 0
            }
        ]
        [ Str "(Makarchev"
        , Space
        , Str "et"
        , Space
        , Str "al."
        , Space
        , Str "2022)"
        ]
    , Str ","
    , Space
    , Str "and"
    , Space
    , Str "cite"
    , Space
    , Str "a"
    , Space
    , Str "Chinese"
    , Space
    , Str "article"
    , Space
    , Cite
        [ Citation
            { citationId = "luohongyun2018"
            , citationPrefix = []
            , citationSuffix = []
            , citationMode = NormalCitation
            , citationNoteNum = 2
            , citationHash = 0
            }
        ]
        [ Str "(\32599\32418\20113"
        , Space
        , Str "et"
        , Space
        , Str "al."
        , Space
        , Str "2018)"
        ]
    , Str "."
    ]

Because @luohongyun2018 is a Chinese bibliography, I want to replace the last English et al. followed it, i.e.:

, Str "et"
, Space
, Str "al."

to an Chinese word 等:

, Str "\31561"

Is it possible to make it via Lua filter? Following the example in the Lua filter page, I have tried but didn’t make it by myself.

Any suggestions would be appreciated. Thanks in advance.

Answer 1

The filter below does two things: it checks if the citation text contains Chinese characters and, if so, then continues to to replace the et al..

The test for Chinese characters is a bit fragile; it could be made more robust by using the utf8.codepoint function from standard Lua library instead.

function Cite (cite)
  return cite:walk{
    Inlines = function (inlines)
      local has_cjk = false
      inlines:walk {
        Str = function (s)
          has_cjk = has_cjk or
            pandoc.layout.real_length(s.text) > pandoc.text.len(s.text)
        end
      }
      -- do nothing if this does not contain wide chars.
      if not has_cjk then
        return nil
      end

      local i = 1
      local result = pandoc.Inlines{}
      while i <= #inlines do
        if i + 2 <= #inlines and
          inlines[i].text == 'et' and
          inlines[i+1].t == 'Space' and
          inlines[i+2].text == 'al.' then
          result:insert(pandoc.Str '等')
          i = i + 3
        else
          result:insert(inlines[i])
          i = i + 1
        end
      end
      return result
    end
  }
end