Use \protected@edef to expand \thepage at cleveref firstaid

[Sophanatprime]

Brief Outline of the Enhancement

If the user redefines \thepage with a \protect macro, an issue arises with \label. Below is a minimal example that demonstrates the problem:

\RequirePackage{latexbug}
\documentclass{book}
\usepackage{cleveref}

\renewcommand{\thepage}{\textbf{\arabic{page}}}

\begin{document}

Text\label{error}.

\end{document}

The LaTeX team has already patched \label@noarg and \label@optarg. Would it be possible to use \protected@edef to expand \thepage instead of \edef? This change could potentially resolve the issue.

Related issue: #1382

Relevant lines of code:

latex2e/required/firstaid/latex2e-first-aid-for-external-files.dtx

Lines 691 to 703 in b34260d

	\AddToHook{begindocument}[cleveref]{%
	\def\label@noarg#1{%
	\cref@old@label{#1}%
	\@bsphack%
	\edef\@tempa{{page}{\the\c@page}}%
	\setcounter{page}{1}%
	\edef\@tempb{\thepage}%
	\expandafter\setcounter\@tempa%
	\cref@constructprefix{page}{\cref@result}%
	\protected@write\@auxout{}%
	{\string\newlabel{#1@cref}{{\cref@currentlabel}%
	{[\@tempb][\arabic{page}][\cref@result]\thepage}{}{}{}}}% <----- five
	\@esphack}%

[FrankMittelbach]

This change could potentially resolve the issue.

could or does? Anyway, I agree with you that the firstaid should be a bit more careful as it is not known what is inside \thepage

[u-fischer]

The example errors already e.g. in texlive 2018 and the \edef is in the original code and this bug been reported more than once. I'm not quite sure if we should start package maintenance through the firstaid.

[FrankMittelbach]

We should not in general, but if we do some firstaid anyway, we might well do it in a way that it is less broken :-) after all, if somebody tried to fix that bug in his or her preamble our firstaid would overwrite that again, wouldn't it?