How to remove part number in TOC with \DeclareTOCStyleEntry

Question

The part title in my case does not need a part number. I use already an \DeclareTOCStyleEntryand would like to remove the part number. using\nullfont` does the trick, but the result is indented. To counteract with a negative indent seems not a good solution. What is better?

p.s. why does \gobble not work?

\documentclass{scrbook}
\KOMAoptions{paper=      
    128.5mm:198.4mm, %(5,06" x 7,91")  %ziel
    DIV=9,  %ziel kleines buch 
    fontsize=12pt,
}

%%%% Sprache
\usepackage[german]{babel}  %scheint 

%%%%% table of content
\setcounter{tocdepth}{0} %   1 gibt parts und chapter und sections

\DeclareTOCStyleEntry[
    indent=-2em,
    entryformat=\mdseries\Large,
    entrynumberformat=\nullfont, % \gobble,
    pagenumberformat=\normalfont\normalsize, 
    onstarthigherlevel=\vskip   ]{tocline}{part}
\DeclareTOCStyleEntry[
    indent=2em,
    pagenumberformat=\normalfont,
    beforeskip=1pt plus .2pt,
    entryformat=\normalfont
    ]{tocline}{chapter}

\begin{document}
    \frontmatter
        \tableofcontents
    \mainmatter
        \part{ Philosophie}
        \chapter{  \textit{Vom Schreiben}}
        \chapter{Zwei}
\end{document}

Answer 1

If you don't want to have parts without numbers but with an entry in the toc you should use the \addpart directive instead of \part or \part*.

Indenting the toc entries is indeed bad typography.

Ragarding gobble. gobble is the name of a specific style of toc entries. In your example you choose the tocline style. But there are even more styles available as the reference manual of koma will tell you. Keep in mind that not all options that are set with DeclareTOCStyleEntry are available for every style. This is also described in the manual.

In the following example a few settings are combined to get a clean looking table of contents.

\documentclass[10pt]{scrbook}

\KOMAoptions{paper=      
    128.5mm:198.4mm, %(5,06" x 7,91")  %ziel
    DIV=9,  %ziel kleines buch 
    fontsize=11pt,
}

%%%% Sprache
\usepackage[german]{babel}  %scheint 
\usepackage{eqparbox}

\setkomafont{chapterentry}{\small}

%%%%% table of content
\setcounter{tocdepth}{0} %   1 gibt parts und chapter und sections

\DeclareTOCStyleEntry[
    % bad typography
    % indent           = -2em,
    entryformat       = {\sffamily\bfseries Part\hskip 2.5ex},
    beforeskip        = 2.25em plus 1pt,
    %entrynumberformat = \nullfont,
    %pagenumberformat  = \normalfont,
    pagenumberbox     = \phantom,
    %
    % onstartentry and onstarthigherlevel are not defined for
    % for 'tocline'
    %
    %onstarthigherlevel = \vskip,
    %onstartentry = Teil
]{tocline}{part}

\DeclareTOCStyleEntry[
    % bad typography
    % indent          = 2em,
    % pagenumberformat = \normalfont,
    beforeskip       = 1em plus 1pt,
    %entryformat      = \normalfont,
    linefill         = \dotfill
]{tocline}{chapter}

\renewcommand*\partpagestyle{empty}

\begin{document}

\frontmatter
\begingroup
    \setkomafont{chapter}{\large\bfseries\sffamily}
    \setkomafont{chapterentry}{\sffamily}
    %\setkomafont{disposition}{\sffamily\itshape}
    \tableofcontents
\endgroup
\mainmatter
\addpart{Philosophie}
\chapter{Vom Schreiben}
\chapter{Zwei}
\addpart{Kilosophie}
\chapter{Vom Schreiben}
\chapter{Zwei}

\end{document}

Answer 2

KOMA-Script does not provide \gobble - so it is undefined in your MWE.

Do you really want to remove the part number only in TOC, but not in the document? Then you can define a new command that takes one argument and does nothing:

\newcommand*\hideentrynumber[1]{}

Use this macro as value for option entrynumberformat

entrynumberformat=\hideentrynumber.

To remove the space reserved for the part number, you have to set the number width to 0pt:

numwidth=0pt

Example:

\documentclass{scrbook}
\KOMAoptions{
  paper=128.5mm:198.4mm,
  fontsize=12pt,
  DIV=9% last option -> recalculates typearea
}
\usepackage[german]{babel}% wirklich die alte Rechtschreibung?

\setcounter{tocdepth}{\chaptertocdepth}% only parts and chapters in ToC

\newcommand*\hideentrynumber[1]{}
\DeclareTOCStyleEntry[
    entryformat=\mdseries\Large,
    entrynumberformat=\hideentrynumber,
    numwidth=0pt,
    pagenumberformat=\normalfont\normalsize
  ]{tocline}{part}
\DeclareTOCStyleEntry[
    indent=1em,% decreased to 1em, but: do you really want to indent chapter entries?
    pagenumberformat=\normalfont,
    beforeskip=1pt plus .2pt,
    entryformat=\normalfont
    ]{tocline}{chapter}

\begin{document}
\layout
\frontmatter
\tableofcontents
\mainmatter
\part{Philosophie}
\chapter{\textit{Vom Schreiben}}
\chapter{Next Chapter}
\part{Next Part}
\chapter{Foo}
\chapter{Bar}
\end{document}

Additional remark: I have removed onstarthigherlevel=\vskip because there was no dimension given for the skip. But even if there would be something like onstarthigherlevel=\vskip 1em, if would do nothing: KOMA-Script does not provide a lower level than part, ie the level of part is -1 and there are no ToC levels ≤-2. Maybe you want to change the beforeskip for the part entry? Default is 2.25em plus 1pt.