How do I do conditional YAML frontmatter, e.g. based on profile?

[pchr8]

Description

Use-case: better multilingual support is my current problem, but I think would be useful in many cases.

Currently, one can do per-language alternates, as shown in the documentation:

---
title: "My Document"
author: "Norah Jones"
date: 5/22/2022
lang: fr
language:
  en:
    title-block-published: "Updated"
  fr:
    title-block-published: "Mis à jour"
---

Then one can set the language in _quarto-en.yml profile files, and it magically works. (I'm doing an approach similar to https://marioangst.com/de/blog/posts/multi-language-quarto/)

It would be really nice if one could also

---
title: "My Document"
author: "Norah Jones"
date: 5/22/2022
lang: it
language:
  en:
    title: "My post number one"
  it:
    title: "Il mio post numero uno"
---

Or are there other ways to achive something similar? I found no way to use variables inside shortcodes, basically something like {{< meta titles[{{< env QUARTO_PROFILE >}}] >}} won't work (and setting a separate meta variable for the language, and then in another front-matter variable referring to that value won't work as well).

I'm thinking about just having the three titles in the front-matter, and using a lua filter to pick one and set the "main" title based on it, but before I start reading into this — are there any easy solutions I'm missing?

[mcanouil]

If you are using profile, then you can set the title in it.
language is for variables used for translations, so there is not reason for title to be under language.

This being said, this has been extensively discussed already:

• current limitations on profile: Conditional metada for different profiles on a website #4516
• conditional content on format and meta: https://quarto.org/docs/authoring/conditional.html#matching-against-metadata
• multi lingual support: Multilingual websites / books #275
• babelquarto: R package to render multilingual Quarto books #5262
• a duplicate or really close to your discussion: Conditional metada for different profiles on a website #4455

I believe all these issues/discussions summarised various proof of concept and what is currently possible.

[pchr8]

Sorry, I spent hours researching this but somehow missed your first and last link which do answer my question, thank you!

I'll solve this with a Lua filter, checked it out and it's easier than it sounded initially.

Thank you!

[pchr8]

This does what I want, basically, I'll swap prints for real logging etc. but otherwise I have a solution to the problem

---
title: "Publications and Awards"
titles:
  en: "Publications and Awards"
  de: "Veröffentlichungen"
filters: [./filters/conditional-metadata.lua]

function Meta(m)
  local profiles = quarto.project.profile
  if not profiles then
    -- TODO: missing YAML key? Empty YAML key?..
    -- TODO even more later: filter multiple profiles to use the language one
    return m
  end

  local profile = profiles[1]
  -- If we have a named profile, save it, otherwise return
  if profile then
    print("Profile: " .. profile)
    m.active_profile = profile
  else
    return m
  end

  if m.titles then
    local titles = m.titles
    if titles[profile] then
      newtitle = pandoc.utils.stringify(titles[profile])
      oldtitle = pandoc.utils.stringify(m.title)
      -- log both if they differ
      if newtitle ~= oldtitle then
        m.title = newtitle
        -- print("Old title:" .. oldtitle)
        -- print("New title:" .. newtitle)
        print(oldtitle .. " => " .. newtitle)
      end
    else
      print("Title for profile " .. profile .. " not found among ")
      for lang, title in pairs(titles) do -- Table iteration.
        print("    " .. lang .. ": " .. pandoc.utils.stringify(title))
      end
    end
  end

  return m
end

[mcanouil]

Thanks for sharing what works for you!