Hide \thechapter for unnumbered Chapters

Question

I want to display my Chapter-Numbers on the right below the Title. I came to the following minimal working example:

\documentclass{article}
\usepackage{titlesec}
\usepackage{marginnote}
\usepackage{lipsum} % for dummy text only
\titleformat{\section}[block]{\LARGE\selectfont}{}{0em}{}[\marginnote{\Huge\thesection}]

\begin{document}
    \section{First section with\\linebreak}
        \lipsum[2]
    \section*{Unnumbered}
        \lipsum[12]
    \section{Three}
        \lipsum[5]
\end{document}

However the unnumbered section now gets numbered as 1. How can I suppress \thesection for unnumbered sections? When I move the \marginnote to the <label> field in \titleformat the Number 'ignores' that the Title contains linebreaks and is positioned relative to the first line.

Answer 1

You can test whether the * version is being used by

\makeatletter
\titleformat{\section}[block]{\LARGE\selectfont}{}{0em}{}[\if\ttl@key@numberless\marginnote{\Huge\thesection}\fi]
\makeatother

as \ttl@key@numberless is // for numbered form so the \if is true as the same character appears twice, and it is /* for the unnumbered section so the \if compares / and * which are false.