Recompiling on another newer iMac I obtain error: "./LibroOrange.tex:187: Package etoolbox Error: Toggle 'blx@lang@captions@latin' undefined."

Question

Recompiling on another newer iMac my big book, I obtain error:

./LibroOrange.tex:187: Package etoolbox Error: Toggle 'blx@lang@captions@latin'  undefined.

But pressing RETURN seems to solve: the compiler continues and the pdf is generated apparently in the right way.

Ideas?

Answer 1

Ulrike Fischer already linked to Cannot use polyglossia/babel with biblatex in LuaTeX: etoolbox Toggle undefined in the comments and that is indeed the same issue. The bug was fixed version 3.16 of biblatex.

Update you TeX system to get rid of this error.

---

Old answer with workaround in case you are stuck with an old version of biblatex.

Since there was some confusion about whether or not the answer applies only for polyglossia, here is an example using babel.

The core of the answer is to have the line

\providetoggle{blx@lang@captions@<language>}

if the main document language <language> has no biblatex localisation file (.lbx file). (That explains why there is an error with latin, for which there is no .lbx file, but not with ngerman, french, or english, all of which have an .lbx file.)

The following example compiles without error again

\documentclass[latin]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[style=authoryear, backend=biber]{biblatex}
\providetoggle{blx@lang@captions@latin}
\addbibresource{biblatex-examples.bib}
\begin{document}
Arma virumque cano \autocite{sigfridsson}
\printbibliography
\end{document}