[FR] How to manage languages in a PDF Quarto book that has chapters with different languages?

See the discussion at

• https://github.com/quarto-dev/quarto-cli/discussions/13013

^{the following is a sumup of what has been originally posted by KleinWurm July 1, 2025}

I am trying to write a Quarto book in French but some of its chapter are in English.

(...)

Using instruction from Document Language, I used the file _quarto.yml as follows:

project:
  type: book

book:
  title: "La marmotte"
  chapters:
    - index.qmd
    - en_chapter.qmd
    - fr_chapter.qmd
    - references.qmd

bibliography: references.bib
lang: fr-FR # main language (for references, lof and lot, etc.)

format:
  pdf:
    documentclass: scrreprt
    lof: true

editor: visual

For the chapters written in another language, I put the following at the top of the chapter file:

---
lang: en-GB # this chapter uses a different language than the main book.
---

A reproducible example is available here: https://github.com/KleinWurm/quarto-book-languages-test/

---

For this kind of usage, setting lang attribute is not working in single file book like PDF, as global lang will be override by chapter one.

Using Pandoc's lang solution with fenced div works (https://pandoc.org/MANUAL.html#language-variables)

::: {lang="en-EN"}
something in english in a french doc
:::

However, Quarto does not integrate with that and Cross reference won't be in English in this chapter : Our document language approach is only global (https://quarto.org/docs/authoring/language.html

IDEAS for Quarto to support this kind of multi language

Support lang in a chapter

Quarto could catch this YAML meta as it is doing for title or other, instead of passing it through. This way it could create the fenced div for the user for the whole chapter.

So a user would write

---
lang: en-GB 
---

Content of the chapter

instead of

::: {lang='en-GB'}
Content of the chapter
:::

more idiomatic to set attribute on the page with Quarto.

Though, how would this behave in multi file book.

Add support for document language change for Pandoc's block with language attributes

Depending on how our document language feature works, could we catch the Div with lang attribute and go use the other _language-<lang>.yml file information to use for the reference on the page. This would be limited to cross reference language and other in page translatation.

This issue is for storing this two ideas in case other usage or 👍 are coming for this.

Start with the linked discussion, the reproducible example, and the _quarto.yml configuration to understand the current chapter-language behavior. Compare the chapter lang metadata with Pandoc's fenced-div language solution and Quarto's document-language guidance. The scope and expected behavior for multi-file books, cross-references, and translated labels need to be decided before implementation.