How to call one lua filter from another lua filter in a different file

[adamiturabi]

Description

I have one lua filter footnotesize.lua that encloses a span with {\footnotesize ...} for latex output:

function ftsize(el)
    if FORMAT:match 'latex' then
      contents = el.content
      table.insert(contents, 1, pandoc.RawInline('latex', '{\\raggedright {\\footnotesize '))
      table.insert(contents, pandoc.RawInline('latex', '}}'))
    end
    return contents
end
Span = function (el)
  if el.classes:includes 'ftsize' then
    return ftsize(el)
  end
end

For html output it does nothing but my styles.css handles the fontsize:

.ftsize {
  font-size: 0.8em;
}

I have another lua filter citex.lua in which I want to call the filter in footnotesize.lua:

Span = function (el)
  if el.classes:includes 'citex' then
    --return pandoc.Span({"["} .. el.content .. {"]"}, {class="ftsize"})
    return ftsize(pandoc.Span({"["} .. el.content .. {"]"}, {class="ftsize"}))
  end
end

I would like to call the ftsize filter from the citex filter.

I've tried calling the ftsize() function directly, and also tried to return a new Span with the ftsize class in the hopes that it woud call the ftsize filter. Neither works. If this is possible, how may I accomplish it?

Here is my test .qmd file:

---
title: "Quarto Basics"
keep-md: true
format:
  html:
    css: styles.css
  pdf:
    keep-tex: true

filters:
  - footnotesize.lua
  - citex.lua
---

Here is an example using ftsize:

[some ref]{.ftsize}

Here is an example using citex:

[some ref]{.citex}

Thank you

[mcanouil]

Make your function external to your filter and import the Lua module inside your filters.

local utils = require("relative/path-to/file.lua")

source: https://www.lua.org/pil/8.1.html

This being said, I'm not sure to understand why you would make two filters in the first place here while one seems to be enough to handle both cases.

[adamiturabi]

Thank you. I'll try this.

This being said, I'm not sure to understand why you would make two filters in the first place here while one seems to be enough to handle both cases.

You're right. The filters in my example are pretty trivial. But I have more complex filters that I would like to call in this way, e.g., those that deal with transliteration, and support for other languages.

Some of those are actually in an extension. (In an _extensions directory with an _extension.yml file.) So I would like to call the filters in the extension from other, external, filters.

Will your solution work in that case as well?

[mcanouil]

It should. That's how Lua works.

The main issue with "external filters", which beside meaning very different things, mainly means the path to the Lua files will change according to how the extension is installed.
So, if you really want to create a dependency tree of your extensions, then I highly suggest you do so using the extension embedding mechanism:

• https://quarto.org/docs/journals/formats.html#extension-embedding

[cderv]

A note that there is a Quarto Lua API to help resolve path for extension resources: quarto.utils.resolve_path(path)
From https://quarto.org/docs/extensions/lua-api.html#utility-functions

Compute the full path to a file that is installed alongside your extension’s Lua script. This is useful for internal resources that your filter needs but should not be visible to the user.

So this could be used to get the path to the lua filter.