[luatex] Duplicated textdir's

[Javier Bezos]

Consider the following document:

\documentclass{article}
\begin{document}
one {{\textdir TRT two} three} four
\end{document}

I get "one owt three four", as expected. Now consider:

\documentclass{article}
\begin{document}
one {{\textdir TRT \textdir TRT two} three} four
\end{document}

The result is "one rouf eerht owt" (ie, the textdir
is set globally).

Is this the intended behaviour? I don't find the logic
behind it. (Tested with TL15 and TL16.)

Javier