How to use commands or multiline values for package options/parameters?

Question

I would like to know if there's a way to use a command (including custom commands created with \newcommand) as parameter/option values). I would like to do something like this

\usepackage[someoption=\somecommand]{somepackage}
\usepackage[supporters={First line\\ Second Line}]{someotherpackage}

Answer 1

If you load the xkvltxp (or kvoptions-patch or catoptions) package before \documentclass, you will be fine: you can pass commands as values of options. To load a package before \documentclass, you should of course use \RequirePackage instead of \usepackage.

Answer 2

Two options

1. You can check to see if a csname is defined using \ifdef in the package, so that defining \csname as a macro before invoking \usepackage can be checked. This isn't exactly what you asked, but it should, I guess, do what you want;
2. You can pass the name of a command as a string without the backslash (say, to \input) in the options, and then bind the command using \edef\inputcs{\def\passname#1{\csname#1\endcsname}\expandafter\passname\input}.