[greek]babel + cleveref + Roman pagenumbering + label = ☇

Question

Feeding

\documentclass{article}
\usepackage[greek]{babel}%%% greek should not necessarily be the main language; e.g., [greek, ngerman] would also expose the bug.
\usepackage{cleveref}%%% option [ngerman] would not change the outcome.
\begin{document}
\pagenumbering{Roman}
\label{someLabel}
\end{document}

as mwe.tex to pdflatex leads to

! Incomplete \iffalse; all text was ignored after line 6. \fi <*> mwe

?

Versions:

• pdfTeX, Version 3.141592653-2.6-1.40.22 (TeX Live 2022/dev/Debian)
• LaTeX2e <2021-06-01> patch level 1
• cleveref 0.21.4 or 0.21.5 (both expose the bug)
• greek.ldf 2020/11/10 v1.10
• babel 2021/07/22 3.63

The bug occurs in current Debian testing "bookworm": https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=997024

The maintainers of cleveref, greek.ldf, and babel have been informed. Meanwhile, any workaround?

Answer 1

The problem is in the \ensureascii macro. You can make it \protected.

\documentclass{article}
\usepackage[greek]{babel}
\usepackage{etoolbox}
\usepackage{cleveref}

\AtBeginDocument{\robustify\ensureascii}

\begin{document}

\pagenumbering{Roman}
\label{someLabel}

\end{document}

Answer 2

You can restore the original Roman counter formatting:

\documentclass{article}

\makeatletter
\let\@RomanSaved\@Roman
\usepackage[greek]{babel}%%% greek should not necessarily be the main language; e.g., [greek, ngerman] would also expose the bug.
\usepackage{cleveref}%%% option [ngerman] would not change the outcome.
\let\@Roman\@RomanSaved
\makeatother

\begin{document}
\pagenumbering{Roman}

\setcounter{page}{5}

\label{someLabel}
{\fontencoding{T1}\selectfont\pageref{someLabel}}
\end{document}