Output for bibliography translator using biblatex and polyglossia

Question

I get some strange behavior when trying to display a translator in my biblography. The german "Übers. v." is set to a a "V" with two dots above it.

I think it happens due to the latin language which is loaded by polyglossia ans which is later needed in the document. If I remove \setotherlanguage[variant=classic]{latin} all is fine. But I don't really understand why biblatex doesn't simply use the mainlanguage? Has anyone an idea how this could be solved?

Here's my MWE and my Bibliography file:

\documentclass[11pt, pagesize=false]{scrbook}
\usepackage{fontspec}

\usepackage{polyglossia}
    \setdefaultlanguage{german}
    \setotherlanguage[variant=classic]{latin}
    \setotherlanguage[variant=ancient]{greek}

\setmainfont[Numbers=OldStyle]{TeX Gyre Pagella}

%Bibliographie und Abbildungen
\usepackage[style=authoryear,backend=biber, isbn=false]{biblatex}
\bibliography{test-Biblio}

%BEGIN DOCUMENT
\begin{document}
\nocite{bruni_interpretatione_2008}
\printbibliography

\end{document}

And the bib file:

@book{bruni_interpretatione_2008,
    Address = {Ottawa},
    Author = {Bruni, Leonardo},
    Date-Added = {2018-08-27 12:05:41 +0200},
    Date-Modified = {2018-08-27 12:05:41 +0200},
    File = {Katalog plus - Universit{\"a}tsbibliothek Freiburg:/Users/moritzheffter/Library/Application Support/Zotero/Profiles/yc5solgb.default/zotero/storage/U95MWV98/Results.html:text/html},
    Isbn = {978-2-7603-3037-5},
    Keywords = {Quelle},
    Langid = {german},
    Publisher = {Les Presses de l'Univ. d'Ottawa},
    Series = {Collection {Regards} sur la traduction},
    Title = {De interpretatione recta -- {De} la traduction parfaite},
    Translator = {Le Blanc, Charles},
    Year = {2008}}

Answer 1

This is caused by a bug in polyglossia reported in January 2017: https://github.com/reutenauer/polyglossia/issues/172 The bug only occurs with XeLaTeX, LuaLaTeX is not affected.

latin.ldf erroneously sets \classicuclccodes (defined as \def\classicuclccodes{\lccode`\V=`\u \uccode`\u=`\V}) in the current scope whenever the language is loaded with variant=classic or variant=medieval. But the \uccode and \lccode should only be redefined within the language extras and should be cleaned up afterwards (like in gloss-classiclatin.ldf) so that they only apply to Latin text and not to other languages as well.

Here the problem was that biblatex needs \uppercase/\MakeUppercase for automatic capitalisation of "übers. von" with the wrong settings active the "ü" is converted to a "V" with two dots above.

If you don't need the "U/V" feature of polyglossia you can turn it off after you load latin with an explicit variant option (and indeed every time you explicitly request a Latin variant) with \noclassicuclccodes.

\documentclass[11pt, pagesize=false]{scrbook}
\usepackage{fontspec}

\usepackage{polyglossia}
    \setdefaultlanguage{german}
    \setotherlanguage[variant=classic]{latin}
    \noclassicuclccodes % work around https://github.com/reutenauer/polyglossia/issues/172
    \setotherlanguage[variant=ancient]{greek}

\setmainfont[Numbers=OldStyle]{TeX Gyre Pagella}

\usepackage[style=authoryear,backend=biber, isbn=false]{biblatex}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{bruni_interpretatione_2008,
    Address = {Ottawa},
    Author = {Bruni, Leonardo},
    Isbn = {978-2-7603-3037-5},
    Keywords = {Quelle},
    Langid = {german},
    Publisher = {Les Presses de l'Univ. d'Ottawa},
    Series = {Collection {Regards} sur la traduction},
    Title = {De interpretatione recta -- {De} la traduction parfaite},
    Translator = {Le Blanc, Charles},
    Year = {2008}}
\end{filecontents}

\addbibresource{\jobname.bib}

\begin{document}
\nocite{bruni_interpretatione_2008}
\printbibliography
\end{document}