Cleveref's \cpageref with range of labels

Question

cleveref's \cpageref seems to have an issue when it receives three or more labels spanning a range of pages. When this happens, \cpageref prints the first and the last labels (the arguments) instead of the pages it was supposed to print, and issues no warnings about it.

This problem has appeared here on the site, as far back as two years ago (see Incorrect \cpageref result with multiple (3+) references that span a page range and Multi-referencing with cleveref: is \cpageref compression bugged, or am I using it wrong?, there were no answers to either of them). Also, the problem has also been reported upstream, but so far hasn't been dealt with (the problem still affects "Version 0.21.5 (pre-release version)", available at https://www.dr-qubit.org/cleveref.html).

That given, I've also been affected by the issue, and took my own stab at it. And I think I understand the problem and have a fix for it. However, my TeX-fu is quite limited (to be kind), so I'm unsure about it. So, my question here is to ask for confirmation about this from more experienced users.

The issue itself can be reproduced by the following MWE:

\documentclass{article}
\usepackage{cleveref}
\begin{document}
See \cref{tab1,tab2,tab3,tab4} on \cpageref{tab1,tab2,tab3,tab4}.
\clearpage{}
\begin{table}
  \caption{Table 1}
  \label{tab1}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\begin{table}
  \caption{Table 2}
  \label{tab2}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\clearpage{}
\begin{table}
  \caption{Table 3}
  \label{tab3}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\begin{table}
  \caption{Table 4}
  \label{tab4}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\end{document}

Which compiles without errors or warnings, and produces:

Now, where I think the problem lies. In the definition of \@cref, at a certain point, cleveref does the following:

      \ifnum\count@consecutive=1\relax%
        \edef\@tempa{{\@beginref}{\@pos}}%
        \csname @set\cref@variant\expandafter\endcsname\@tempa%
      \else%
        \edef\@tempa{{\@beginref}{\@endref}{\@pos}}%
        \csname @set\cref@variant range\expandafter\endcsname\@tempa%
      \fi%

(I'm on a current TeXLive here, my cleveref.sty has date 2018/03/27 and version 0.21.4, and this occurs in lines 1021 to 1027).

At this point \@cref is looping over a subgroup consecutive labels. \cref@variant is the name of the user facing cleveref macro, which is received as the first argument of \@cref (e.g. cref, Cref, cpageref, etc). So, this is calling a set of macros with names either \@set<variant> or \@set<variant>range.

And we do find most of these explicitly defined in cleveref.sty: \@setcref, \@setCref and \@setlabelcref on lines 1044-1046; \@setcrefrange, \@setCrefrange and \@setlabelcrefrange on lines 1072-1074; \@setcpageref, \@setCpageref and \@setlabelcpageref on lines 1087-1089 (there are still others).

However, I cannot find \@setcpagerefrange, \@setCpagerefrange and \@setlabelcpagerefrange, and I think that's what's missing. Besides, though none of the linked questions mentioned \Cpageref and \labelcpageref, this observation would suggest they would fail in the same way as \cpageref does. And indeed, they do.

Providing them in the MWE above as:

\makeatletter
\newcommand*{\@setcpagerefrange}[3]{%
  \@@setcpagerefrange{#1}{#2}{cref}{#3}}
\newcommand*{\@setCpagerefrange}[3]{%
  \@@setcpagerefrange{#1}{#2}{Cref}{#3}}
\newcommand*{\@setlabelcpagerefrange}[3]{%
  \@@setcpagerefrange{#1}{#2}{labelcref}{#3}}
\makeatother

(Note that the order of the arguments in \@@setcpagerefrange is different from its siblings).

Will now give us expected results:

So, are this diagnostic and this fix correct?

Answer 1

Well, not to leave this one unanswered, to the best of my knowledge, the problem is indeed the one diagnosed in the OP. An attempt of contact with the maintainer with the suggested fix has been made.

\documentclass{article}
\usepackage{cleveref}
\makeatletter
\newcommand{@setcpagerefrange}[3]{%
  @@setcpagerefrange{#1}{#2}{cref}{#3}}
\newcommand{@setCpagerefrange}[3]{%
  @@setcpagerefrange{#1}{#2}{Cref}{#3}}
\newcommand*{@setlabelcpagerefrange}[3]{%
  @@setcpagerefrange{#1}{#2}{labelcref}{#3}}
\makeatother
\begin{document}
See \cref{tab1,tab2,tab3,tab4} on \cpageref{tab1,tab2,tab3,tab4}.
\clearpage{}
\begin{table}
  \caption{Table 1}
  \label{tab1}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\begin{table}
  \caption{Table 2}
  \label{tab2}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\clearpage{}
\begin{table}
  \caption{Table 3}
  \label{tab3}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\begin{table}
  \caption{Table 4}
  \label{tab4}
  \begin{tabular}{cc}
    1 & 2 \
    3 & 4 \
  \end{tabular}
\end{table}
\end{document}