Using quotation marks and exclamation marks

Question

I've got a problem with the combination of (German) quotation marks and exclamation marks in LaTeX. Consider this code:

\documentclass[12pt,twoside,a4paper]{book}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\begin{document}
\glq Nochmal!\grq
\end{document}

Result: 'Nochmal¡

Instead of: 'Nochmal!'

Basically the exclamation mark is upside down and the second quotation mark disappears. Another thing to mention: In some cases it works just fine, while in other cases I get the upside down exclamation mark.

How can I solve this problem?

Answer 1

Another reason why I prefer to use csquotes. This here works fine:

\documentclass[12pt,twoside,a4paper]{book}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage[autostyle]{csquotes}
\begin{document}
\enquote*{Nochmal!}
\end{document}

Edit: I opened an issue https://github.com/latex3/babel/issues/19

Answer 2

It seems that the exclamation mark and \grq form a ligature, because \grq expands to \textquoteleft, which forms this ligature. Same as inputting

!`

Putting anything in between the two, or around one of the two, that suppresses a ligature works, e.g., a \relax in between, an empty group in between, a \hbox around one of the two, etc.