\input regression-test.tex
\documentclass{article}
% "load polyglossia" without a "map", for a selectable language that has no
% direct gloss-<code>.ldf shim in Polyglossia (so the derivation falls back
% to Babel's babel-<code>.ini, cs -> czech): langselect must still recompute
% the mapped target language for \setdefaultlanguage, not just for Babel's
% main= option.
\usepackage[
  languages={en,cs},
  targetlang=cs,
  load polyglossia
]{langselect}
\begin{document}
\START
\TYPE{target=\olsTargetLanguage}
\TYPE{active=\languagename}
\END
\end{document}