Custom Package: Combine Options

Question

Suppose I have the following custom package where I have my various titlesec setups defined:

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mytitles}[2018/06/01 Custom Titles Package]
\RequirePackage{titlesec}

\DeclareOption{titlesone}{
\titleformat{\chapter}%
  [display]{}{\itshape\huge\thechapter}{0pt}{}[]

\titleformat{\section}%
  [hang]{\Large\itshape}{\thesection}{1em}{}[]
}

\DeclareOption{titlestwo}{
\titleformat{\chapter}%
  [display]{}{\bfseries\huge\thechapter}{0pt}{}[]

\titleformat{\section}%
  [hang]{\Large\itshape}{\thesection}{1em}{}[]
}

\DeclareOption{titlesthree}{
\titleformat{\chapter}%
  [display]{}{\itshape\huge\thechapter}{0pt}{}[]

\titleformat{\section}%
  [hang]{\Large\bfseries}{\thesection}{1em}{}[]
}

\DeclareOption{titlesfour}{
\titleformat{\chapter}%
  [display]{}{\bfseries\huge\thechapter}{0pt}{}[]

\titleformat{\section}%
  [hang]{\Large\bfseries}{\thesection}{1em}{}[]
}

\ExecuteOptions{titlesone}
\ProcessOptions\relax
\endinput

And then:

\documentclass[12pt, a4paper]{book}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[american]{babel}
\usepackage{microtype}
\usepackage{libertine}
\usepackage{lipsum}
\usepackage[titlestwo]{mytitles}


\begin{document}
\chapter{Test Chapter}
\section{Test Section}
\subsection{Test Subsection}
\lipsum
\end{document}

The problem: Suppose I have five different chapter definitions, and five different section definitions. Further suppose that I am like to use any combination. With my extremely limited knowledge, the way I do is to \DeclareOption for each combination. (In this case, twenty five.) Would it be possible to declare options for chapter and section separately, and load them with something like: \usepackage[chapteroptionthree, sectionoptionfour]{mytitles}?

Answer 1

Edited: If you have way too many options, I suggest using the key value syntax. Without the key value syntax, you would write

\usepackage[chapteroptionthree, sectionoptionfour]{mytitles}

But with the key value syntax, you would write

\usepackage[chapteroption=3, sectionoption=4]{mytitles}

Solution with key value syntax

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mytitles}[2018/06/30 Custom Titles Package]

\RequirePackage{kvoptions}% https://ctan.org/pkg/kvoptions

\SetupKeyvalOptions{
  family=mytitles,
  prefix=mytitles@
}

\DeclareStringOption[1]{chapteroption}[1]
\DeclareStringOption[1]{sectionoption}[1]

\ProcessKeyvalOptions*

\RequirePackage{titlesec}

\ifnum\mytitles@chapteroption=1
  \titleformat{\chapter}%
    [display]{}{\itshape\huge\thechapter}{0pt}{}[]
\else
  \ifnum\mytitles@chapteroption=2
    \titleformat{\chapter}%
      [display]{}{\bfseries\huge\thechapter}{0pt}{}[]
  \else
    \ifnum\mytitles@chapteroption=3
      \titleformat{\chapter}%
        [display]{}{\itshape\huge\thechapter}{0pt}{}[]
    \else
      \ifnum\mytitles@chapteroption=4
        \titleformat{\chapter}%
          [display]{}{\bfseries\huge\thechapter}{0pt}{}[]
      \else
        \PackageWarningNoLine{mytitles}{%
          Key value `chapteroption=\mytitles@chapteroption'\MessageBreak
          does not exist!%
        }%
      \fi
    \fi
  \fi
\fi

\ifnum\mytitles@sectionoption=1
  \titleformat{\section}%
    [hang]{\Large\itshape}{\thesection}{1em}{}[]
\else
  \ifnum\mytitles@sectionoption=2
    \titleformat{\section}%
      [hang]{\Large\itshape}{\thesection}{1em}{}[]
  \else
    \ifnum\mytitles@sectionoption=3
      \titleformat{\section}%
        [hang]{\Large\bfseries}{\thesection}{1em}{}[]
    \else
      \ifnum\mytitles@sectionoption=4
        \titleformat{\section}%
          [hang]{\Large\bfseries}{\thesection}{1em}{}[]
      \else
        \PackageWarningNoLine{mytitles}{%
          Key value `sectionoption=\mytitles@sectionoption'\MessageBreak
          does not exist!%
        }%
      \fi
    \fi
  \fi
\fi

\endinput

Solution without key value syntax

Simply write 8 options (your example contains only 4) for chapter and section formatting, and then you have access to all 4*4=16 combinations.

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{mytitles}[2018/06/30 Custom Titles Package]
\RequirePackage{titlesec}

\DeclareOption{chapteroptionone}{
\titleformat{\chapter}%
  [display]{}{\itshape\huge\thechapter}{0pt}{}[]}
\DeclareOption{sectionoptionone}{
\titleformat{\section}%
  [hang]{\Large\itshape}{\thesection}{1em}{}[]}

\DeclareOption{chapteroptiontwo}{
\titleformat{\chapter}%
  [display]{}{\bfseries\huge\thechapter}{0pt}{}[]}
\DeclareOption{sectionoptiontwo}{
\titleformat{\section}%
  [hang]{\Large\itshape}{\thesection}{1em}{}[]}

\DeclareOption{chapteroptionthree}{
\titleformat{\chapter}%
  [display]{}{\itshape\huge\thechapter}{0pt}{}[]}
\DeclareOption{sectionoptionthree}{
\titleformat{\section}%
  [hang]{\Large\bfseries}{\thesection}{1em}{}[]}

\DeclareOption{chapteroptionfour}{
\titleformat{\chapter}%
  [display]{}{\bfseries\huge\thechapter}{0pt}{}[]}
\DeclareOption{sectionoptionfour}{
\titleformat{\section}%
  [hang]{\Large\bfseries}{\thesection}{1em}{}[]}

\ExecuteOptions{chapteroptionone}
\ExecuteOptions{sectionoptionone}
\ProcessOptions\relax
\endinput