\begin{otherlanguage}{<lang>} loaded with [main=<lang>] no longer works

[PhelypeOleinik]

Until the previous babel release this would work:

\documentclass{article}
\usepackage[main=brazil]{babel}
% \usepackage[brazil]{babel} % works
\begin{document}
\begin{otherlanguage}{brazil}
\end{otherlanguage}
\end{document}

but after today's (2020-10-05) update, it errors with:

! Package babel Error: You haven't defined the language brazil yet.
(babel)                Perhaps you misspelled it or your installation
(babel)                is not complete.

[jbezos]

Hopefully, not many people is using babel in this way. Anyway I'll try to fix it asap.

[PhelypeOleinik]

Yes, it's a slightly unusual setup I have for a two-language document, but still, main=<lang> doesn't set the language for the body of the document (\languagename is nil). Thanks for looking into it!

[jbezos]

I'd say it's a severe bug because in many cases the language is silently ignored. Very likely I'll submit the fix to CTAN tomorrow.

[PhelypeOleinik]

Oh, that was fast :-) Thank you!