KOMA-Script have parskip=full- but no spacing between section title and content

Question

When using KOMA-Script, one has \RedeclareSectionCommand available to adjust the spacing before/after section titles, as described in this question.

I want the content of the section to appear on the immediate next line under the section title, without any extra vertical space. The following mwe shows the content as I want it:

\documentclass{scrartcl} 
\begin{document}

\RedeclareSectionCommand[afterskip=1pt]{section} %the magic happens here

\section{Foo}
    This is some text to show off
\section{Bar}
    This is some text to show off
\section{Baz}
    This is some text to show off  
\end{document}

In my actual document however, I use parskip=full- as argument to \documentclass. This has the effect, that there will be an empty line between the section title and the section content, which I don't want. The mwe also shows this behaviour. Every allowed value for parskip with starts with full or half shows this behaviour.

I think this is the normal and expected behaviour, as the german documentation explicitly states that the whitespace preceedes the paragraph.

Because time is an issue right now, I hacked it by putting \vspace*{-\baselineskip} after every \section{}, but this is of course unacceptable for long term use.

How do I get the behaviour of parskip=full- and \RedeclareSectionCommand[afterskip=1pt]{section}, with the exception that I don't want any vertical space between the section title and the corresponsing content?

Answer 1

Update

It is still not recommanded but now possible without patching a command because KOMA-Script version 3.26 introduces two new keys to \RedeclareSectionCommand and \RedeclareSectionCommands: runin and afterindent. Possible values for both keys are bysign, true and false. For more information see the KOMA-Script documentation or eg Adjusting spacing around section/subsection titles with koma-script.

Using the new key runin with value false¹ it is possible to remove the \parskip between the heading and the following text by afterskip=-\parskip.

Example:

\documentclass[parskip=full-]{scrartcl}[2015/10/03]
\RedeclareSectionCommand[
  runin=false,
  afterskip=-\parskip
]{section}

\begin{document}
\section{Foo}
    This is some text to show off

    This is some text to show off
\section{Bar}
    This is some text to show off

    This is some text to show off
\section{Baz}
    This is some text to show off

    This is some text to show off
\end{document}

The (ugly) result is the same as in the original answer below.

¹ Default setting is runin=bysign which results in the same behavior as in the original answer.

---

Original answer

It is not recommended - see tex.stackexchange.com/a/300541/43317 and komascript.de/node/2039 (German) - but possible with KOMA-Script version 3.19 or newer:

\documentclass[parskip=full-]{scrartcl}[2015/10/03]
\RedeclareSectionCommand[afterskip=1sp]{section} %the magic happens here
\usepackage{xpatch}
\xapptocmd\sectionlinesformat{\vspace*{-\parskip}}{}{\PatchFailed}

\begin{document}
\section{Foo}
    This is some text to show off

    This is some text to show off
\section{Bar}
    This is some text to show off

    This is some text to show off
\section{Baz}
    This is some text to show off

    This is some text to show off
\end{document}

As you can see the result looks weird: