catoptions causes option clash with xcolor

Question

Look at the following example:

\documentclass{scrartcl}

\usepackage{filecontents}
\begin{filecontents}{my1.sty}
   \RequirePackage{xcolor}
   \RequirePackage{catoptions}
\end{filecontents}
\begin{filecontents}{my2.sty}
   \RequirePackage{xcolor}
\end{filecontents}


\usepackage[cmyk]{xcolor}
\usepackage{my1}
\usepackage{my2}

\begin{document}
   \rule{2cm}{2cm}
\end{document}

catoptions seems to cause an option clash if there is a \RequirePackage{xcolor} somewhere after it. Everything works fine if I load my2 before my1 but I can’t ensure that this won’t happen.

my1 is a place holder for my menukeys package, my2 is a place holder for any other package requiring xcolor.

Answer 1

There is indeed an option clash for xcolor package in your code. It is easy to see that in your two (actually three) loading rounds of xcolor. Here is the error help:

? h
The package 'xcolor' has already been loaded with options:
  [cmyk].
There has now been an attempt to load it with no options. 
Adding the global options:
  'cmyk'
to your \documentclass declaration may fix this.

The catoptions redefines the LaTeX command \@onefilewithoptions to catch this type of situation. If you don't want it, then I would have to send you a patch. I will then create an option in catoptions to make strick option checking optional. However, I will be reluctant to do that. This is because the following definition by LaTeX isn't robust: when #2 is empty, nothing happens (LaTeX's \@for cannot process empty list).

\def\@if@pti@ns#1#2{%
  \let\reserved@a\@firstoftwo
  \@for\reserved@b:=#2\do{%
    \expandafter\in@\expandafter{\expandafter,\reserved@b,}{,#1,}%
    \ifin@\else\let\reserved@a\@secondoftwo\fi}%
  \reserved@a
}

Answer 2

It is possible to delay the loading of catoptions with etoolbox’ \AtEndPreamble but this doesn’t wokr in the real world since I need some functions of catoptions in my1 (i.e. menukeys)

\documentclass{scrartcl}

\usepackage{filecontents}
\begin{filecontents}{my1.sty}
   \RequirePackage{etoolbox}
   \RequirePackage{xcolor}
   \AtEndPreamble{\RequirePackage{catoptions}}
\end{filecontents}
\begin{filecontents}{my2.sty}
   \RequirePackage{xcolor}
\end{filecontents}


\usepackage[cmyk]{xcolor}
%\usepackage{my2}
\usepackage{my1}
\usepackage{my2}

\begin{document}
   \rule{2cm}{2cm}
\end{document}