Have option conditionally require package

Question

I want to declare an option in my package that, if provided, will require another package. However, just doing

\DeclareOption{requiresomething}{
    \RequirePackage{somepackage}
}

does not work, as you can't mix package requiring with the Option Section. Is there any simple solution to this? Am I doing something wrong?

Answer 1

You can use a conditional:

\ProvidesPackage{aachh}
\newif\ifaachh@array
\DeclareOption{array}{\aachh@arraytrue}
\ProcessOptions\relax
\ifaachh@array
  \RequirePackage{array}
\fi
\endinput

or define a macro

\ProvidesPackage{aachh}
\DeclareOption{array}{\let\aachh@array@empty}
\ProcessOptions\relax
@ifundefined{aachh@array}{}{%
  \RequirePackage{array}%
}
\endinput

The latter method is less memory intensive, but nowadays it's not really important.