How to set multiple languages with babel?

[fredguth]

It is very common to have academic documents with more than one language. In latex we would add:

\usepackage[american, brazil]{babel}

But this is hardcoded! I want the possibility of setting different languages with metadata.
How can I create a metadata field in my book project and pass them as options to babel?

#...
babeloptions:
    - american
    - brazil

[cscheid]

If you control the Pandoc template (that is, you're creating new ones), then your template can get information directly from the metadata, like we describe here: https://quarto.org/docs/journals/templates.html#template-partials. That's probably the best option if you're going to use custom LaTeX packages anyway.

[fredguth]

@cscheid Is the default template.tex this one: https://github.com/quarto-dev/quarto-cli/blob/main/src/resources/formats/pdf/pandoc/template.tex#L249??

This template.tex has (L249):

$if(babel-lang)$
\babelprovide[main,import]{$babel-lang$}
$endif$
$for(babel-otherlangs)$
\babelprovide[import]{$babel-otherlangs$}
$endfor$

I tried adding in my _quarto.yml

...
format:
    pdf:
            babel-lang: brazil
            babel-otherlangs: american

but it didn't add babel to my generated bookfilename.tex file.

I also tried adding to my in-header.tex

$if(abnt.linguas)$
\PassOptionsToPackage{unicode$for(abnt.linguas)$$abnt.linguas$$sep$,$endfor$}{babel}
$endif$
\usepackage[brazil]{babel}

and in _quarto.yml

...
abnt:
    linguas: american

which yields an error: LaTeX Error: Missing \begin{document}.

Strangely, if I change in-header.tex to:

% $if(abnt.linguas)$
% \PassOptionsToPackage{unicode$for(abnt.linguas)$$abnt.linguas$$sep$,$endfor$}{babel}
% $endif$
\usepackage[american,brazil]{babel}

it generates a bookfilename.tex with the \usepackage[american,brazil]{babel} line in it.

[cderv]

@fredguth Just to give some context on how Pandoc is handling multiple langue by default - interesting as we are based on Pandoc's template and leveraging such features.

lang in YAML is used to defined main language to use, and any other language needed for other content in a document is to be set on block or inline basis using lang attributes on Divs or Spans created. This is explain in https://pandoc.org/MANUAL.html#language-variables and here is an example

---
format: pdf
lang: en
keep-tex: true
---

This is in English

::: {lang=fr}
Mais cela est écrit en Français
:::

And another [ejemplo]{lang=es}

In the generated TeX, we get

\ifLuaTeX
\usepackage[bidi=basic]{babel}
\else
\usepackage[bidi=default]{babel}
\fi
\babelprovide[main,import]{english}
\babelprovide[import]{french}
\babelprovide[import]{spanish}

You see that mutliple languages are correctly defined for babel using \babelprovide mechanism (see babel doc)

The specific syntax with Divs or Spans will also make sure that correct LaTeX command is used

This is in English

\begin{otherlanguage}{french}

Mais cela est écrit en Français

\end{otherlanguage}

And another \foreignlanguage{spanish}{ejemplo}

I believe this mechanism work in Quarto, including Books.

Anyway, this is how Pandoc supports mutliple languages with babel.

Did you try this already ?

Hope it helps

[fredguth]

Using pdf.lang: pt-BR generates:

....
\ifLuaTeX
\usepackage[bidi=basic]{babel}
\else
\usepackage[bidi=default]{babel}
\fi
\babelprovide[main,import]{brazilian}
% get rid of language-specific shorthands (see #6817):
\let\LanguageShortHands\languageshorthands
\def\languageshorthands#1{}

But if I add pdf.otherlangs: [en-US, es-MX] these other languages are discarded. I will still try creating a div, but I was looking for a way to set it globally.

[cderv]

But if I add pdf.otherlangs: [en-US, es-MX] these other languages are discarded.

How did you set that ? Is this something Pandoc supports ? are you trying to set globally in YAML ?

If so, I would say the Pandoc variable used internally when you create Divs is babel-otherlangs but that is not documented as mainly for internal usage - so use at your own risk. Setting different language like this globally will not make the LaTeX contains \begin{otherlanguage} or \foreignlanguage though - that is what the div and Spans are for I think

[fredguth]

I included in format.pdf.babel-otherlangs, but I will stop doing that and do your way.

[mcanouil]

For reference:

• How to manage languages in a PDF Quarto book that has chapters with different languages? #13013