Description
Copy from bug report at tex.stackexchange (not my report, but found it when I encountered the same issue):
\documentclass{article}
\usepackage[T5,T1]{fontenc}
\usepackage[vietnamese, british]{babel}
\usepackage{csquotes}
\usepackage{biblatex}
\begin{document}
\foreignlanguage{vietnamese}{Ngô Bảo Châu}
\end{document}
The above code compiles in PDFLaTeX, but I get two warnings:
Package babel Warning: No input encoding specified for Vietnamese on input line 146.
...
Package biblatex Warning: Language 'vietnamese' not supported.
(biblatex) Using dummy definitions on input line 8.
How can I avoid these two warnings?
The first can be removed with \usepackage[utf8]{inputenc}, but I feel like it isn't the correct way: this line should be nowadays obsolete, and there should be a more direct way to tell babel the correct encoding for Vietnamese.
asked Jul 13 at 9:56 by Gargantuar at https://tex.stackexchange.com/q/722463
Comment by David Carlisle:
as far as I can see your workaround for inputenc is what it needs to be (or patch internal commands) you should report it to babel as a bug the file should be updated to check that utf-8 is enabled not just check if inputenc is loaded. for biblatex I think you need to make a lbx file following these steps https://github.com/plk/biblatex/wiki/Checklist-for-submitting-a-new-localisation-file-(.lbx).