Hot to use empty item in description environment?

Question

I am using the description environment to give some extra reasons for the items. However, some items are obvious and don't need reasons. Leaving them empty puts a large blank line, because I have set the descriptions to go on the next line

\documentclass[12pt]{report}

\usepackage{enumitem} % configure labels of items in enumerations i.e. i), ii)
\setlist[description]{style=nextline,font=\normalfont\textbullet\space,labelindent=\parindent}

\begin{document}
\begin{description}
    \item[Obvious item]
    \item[Not so obvious] So we need a small reason, which can span multiple lines lines lines lines lines lines lines lines lines lines lines lines
    \item[Also obvious]
\end{description}
\end{document}

If I'm doing this wrong, any advice is welcome ! :) .

Edit: The ugliest hack so far is to use \item[Obvious item\vspace{-1.5em}] which seems right to my eye™️.

To add: I'm using description with nextline because this kind of respects the logical formatting and I'm thinking of improving the style later (e.g. make the term bold). This would be (I think) more difficult if I used a replacement such as itemize with manual line breaks

Maybe I could patch description to detect empty item description ?

Answer 1

Massage the body so you transform your description into itemize (and get alignment right).

\documentclass[12pt]{report}
\usepackage{environ,xparse}

\ExplSyntaxOn
\NewEnviron{ctdescription}
 {
  % remove possible \par generated by blank lines before \item
  \tl_replace_all:Nnn \BODY { \par\item } { \item }
  % add a trailing delimiter
  \tl_put_right:Nn \BODY { \ct_item_end: }
  % replace \item by \ct_item_end: \ct_item:w
  \tl_replace_all:Nnn \BODY { \item } { \ct_item_end: \ct_item:w }
  % remove the spurious leading \ct_item:w
  \tl_set:Nx \BODY { \tl_tail:N \BODY }
  % produce the environment
  \begin{itemize}\BODY\end{itemize}
 }
\cs_new_protected:Npn \ct_item:w [#1] #2 \ct_item_end:
 {
  \item #1 \tl_if_blank:nF { #2 } { \mbox{} \\ \tl_trim_spaces:n { #2 } }
 }
\ExplSyntaxOff

\begin{document}

\begin{ctdescription}
\item[Obvious item]
\item[Not so obvious] No we need a small reason, which can 
  span multiple lines lines lines lines lines lines lines 
  lines lines lines lines lines
\item[Also obvious]
\end{ctdescription}

\end{document}

Note that a trailing blank line is not allowed, but they're allowed before \item.

Answer 2

An even more ad-hoc proposal: why not forget about description altogether?

\documentclass[12pt]{report}

\begin{document}

\begin{itemize} 
    \item Obvious item
    \item Not so obvious \\
          So we need a small reason, which can span multiple lines lines lines lines lines lines lines lines lines lines lines lines
    \item Also obvious
\end{itemize}

\end{document}

This should produce the displayed output.

Answer 3

A very ad hoc proposal: forget about nextline.

\documentclass[12pt]{report}

\usepackage{enumitem} % configure labels of items in enumerations i.e. i), ii)
\setlist[description]{font=\normalfont\textbullet\space,labelindent=\parindent}

\begin{document}
\begin{description}
    \item[Obvious item]
    \item[Not so obvious]~\\ So we need a small reason, which can span multiple lines lines lines lines lines lines lines lines lines lines lines lines
    \item[Also obvious]
\end{description}
\end{document}