Special characters in kvoptions (like \\)

Question

I try to write a little package for my personal use. For this I use kvoptions. Now I have to give a string to one of the options which contains \\ but this fails with: undefined control sequence. \let \reserved@e.

My texfile looks like this:

\documentclass{scrlttr2}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[myoption={Street\\City}]{mypackage}

\begin{document}
\begin{letter}{some name}
\opening{Dear ...}
\closing{Regards ...}
\end{letter}
\end{document}

And the content of the .sty-file:

\ProvidesPackage{mypackage}
\RequirePackage{kvoptions}
\SetupKeyvalOptions{
    family=mypackage
    ,prefix=mypackage@
}
\DeclareStringOption[]{myoption}[]
\ProcessLocalKeyvalOptions*\relax
\setkomavar{fromaddress}{\mypackage@myoption} %just for example

In reality I do more than just that with myoption but I need it to accept \\ in the string. This is the only problem. As long as I don't use \\ in the strings everything works fine. I can use a default for the option like this:

\DeclareStringOption[Other street\\Other city]{myoption}

Inside of the .sty but the moment I want to enter another value for myoption containing \\ it fails. How is it possible to allow such characters in the options?

EDIT: added the \ProcessLocalKeyvalOptions

Your package misses \ProcessLocalKeyvalOptions*, but that's not the solution — , Jan 07 '17 at 19:02
Oh, just forget that in the MWE... But thanks, I'll edit it :) — Skillmon, Jan 07 '17 at 19:04
really latex doesn't support this (\\ dies in the package loading code before kvoptions can see it.) You'd have to load a package that redefined \usepackage before you used an option in this way — David Carlisle, Jan 07 '17 at 19:07
@DavidCarlisle that's too bad. But thanks for the clarification. Do you by any chance know any package that does that or can pinpoint me in the right direction? — Skillmon, Jan 07 '17 at 19:11
kvoptions ought to but I just tried loading it earlier with no effect, there are other packages that define key=value package option handling (I forget which:-) or just put \let\\\relax before the package load (and put it back afterwards) — David Carlisle, Jan 07 '17 at 19:12
Should have thought of the \let\\\relax myself. Thanks a lot, it works now! You might put this as an answer so I can accept it as one. — Skillmon, Jan 07 '17 at 19:16

score 2 · Accepted Answer · answered Jan 08 '17 at 10:10

You would need to load a package that redefines \usepackage to make this safe before the \usepackage call that uses the option. Unfortunately just loadingkvoptions` earlier doesn't seem to work. There are other packages that define key=value package option handling (I forget which:-) or just put

\let\savednl=\\
\let\\=\relax

before the package load and put it back afterwards with

\let\\=\savednl

then it will be safe during the package option handling, but back to normal by the time you use the option value.

Special characters in kvoptions (like \\)

1 Answers1