[xr-hyper] decouple \externaldocument from hyperref loading state

[mrpiggi]

As I did not find anything on the issue tracker here, I am wondering, if I do anything wrong... Using this MWE, I get warnings both with pdflatex pdfTeX warning (dest): name{section.1} has been referenced but does not exist, replaced by a fixed one as well as lualatex warning (pdf backend): unreferenced destination with name 'section.1' regardless if a prefix with \externaldocument is used or not.

\begin{filecontents}{external.tex}
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{A\label{extlbl}}
\end{document}
\end{filecontents}

\documentclass{article}
\usepackage{xr-hyper}
\externaldocument[ext-]{external}
\usepackage{hyperref}
\begin{document}
\ref{ext-extlbl}
\end{document}

[u-fischer]

Move \externaldocument[ext-]{external} behind hyperref. hyperref redefines some commands of xr-hyper so that it now stores the file name:

\begin{filecontents}{externalA.tex}
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{A\label{extlbl}}
\end{document}
\end{filecontents}
\begin{filecontents}{externalB.tex}
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{A\label{extlbl}}
\end{document}
\end{filecontents}

\documentclass{article}
\usepackage{xr-hyper}
\externaldocument[extA-]{externalA}

\usepackage{hyperref}

\externaldocument[extB-]{externalB}
\ExplSyntaxOn
\tl_show:c{r@extA-extlbl}
\tl_show:c{r@extB-extlbl}
\ExplSyntaxOff

\begin{document}

\ref{extA-extlbl}
\quad
\ref{extB-extlbl}

\end{document}

gives

> \r@extA-extlbl={1}{1}{A}{section.1}{}.

> \r@extB-extlbl={1}{1}{A}{section.1}{externalB.pdf}.

[mrpiggi]

Thanks for the immediate reply and the suggested solution. Would it make sense to use a hook within \XR@@ in order to execute it again after hyperref was loaded or delay it's execution at all after hyperref. This would improve usability a lot.

\begin{filecontents}{externalA.tex}
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{A\label{extlbl}}
\end{document}
\end{filecontents}
\begin{filecontents}{externalB.tex}
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{A\label{extlbl}}
\end{document}
\end{filecontents}

\documentclass{article}
\usepackage{xr-hyper}
\makeatletter
\def\XR@@#1#2#3[#4]{%
  \@ifpackageloaded{hyperref}{}%
    {\AddToHook{package/hyperref/after}{\XR@@{#1}{#2}{#3}[#4]}}%
  {%
  \makeatletter
  \def\XR@prefix{#1}%
   \def\XR@nocite{#2}%
   \ifx\XR@nocite\XR@@nocite
     \let\XR@bibcite\vadjust
   \else
     \let\XR@bibcite\bibcite
   \fi
  \def\XR@URL{#4}%
  \filename@parse{#3}%
  \XR@next#3.aux\relax\\}}
\makeatother
\externaldocument[extA-]{externalA}

\usepackage{hyperref}

\externaldocument[extB-]{externalB}
\ExplSyntaxOn
\tl_show:c{r@extA-extlbl}
\tl_show:c{r@extB-extlbl}
\ExplSyntaxOff

\begin{document}

\ref{extA-extlbl}
\quad
\ref{extB-extlbl}

\end{document}

[u-fischer]

I don't think that this is the right solution. Imho the method used currently by hyperref / xr-hyper to decide if an internal or an external link should be created is flawed. hyperref tests if the fifth argument is empty and this means that external.tex can not simply fill this argument as it would harm its own internal links and xr-hyper has to postprocess the label definitions to smuggle the data in. It would be better if xr-hyper would create some command, e.g. XR@gotor@\XR@prefix<label> with the url info. Then hyperref could test for that, and users would have better options to configure the links. And if would free the fifth argument for better uses.

[mrpiggi]

Well, then this is probably another item on your already well-filled to-do list. Anyway, from a user's point of view, it should not matter whether \externaldocument is used before or after loading the hyperref package.

[u-fischer]

This should now work. The file name is always stored, regardless if and when hyperref is loaded.

[muzimuzhi]

Corresponding commit is c50689b (xr-hyper: always store url/file name, 2023-11-26).