titlesec interferes with the part title in TOC

In this answer, I designed a simple TOC style. However, I find the TOC setting for part doesn’t work normally if the title format for part has been modified by titlesec.

Without titleformat{part}, the TOC looks like (which is the desired result):

However, with titleformat{part}, the TOC becomes:

How can I get the desired effect back?

Below is a MWE.

documentclass{book}

% usepackage{titlesec}
% titleclass{part}{top} % make part like a chapter
% titleformat{part}[display]
%     {filleft}
%     {MakeUppercase{partname}~thepart}
%     {1em}
%     {MakeUppercase}

usepackage{etoolbox}
makeatletter
patchcmd@part% change the part style
  {addcontentsline{toc}{part}{theparthspace{1em}#1}}
  {addcontentsline{toc}{part}{protectnumberline{texorpdfstring{-~thepart~-}{thepart~}}texorpdfstring{MakeUppercase{#1}}{#1}}}
  {}{FAIL}
makeatother

usepackage{titletoc}
titlecontents{part}
    [0em]
    {addvspace{1.5pc}filcenter}
    {thecontentslabel}
    {}
    {} % without page number
    [addvspace{.5pc}]

usepackage[hidelinks,linktoc=all]{hyperref}

begin{document}
ttfamily

tableofcontents

part{First part}

end{document}

documentclass{book}

usepackage[newparttoc]{titlesec}

titleclass{part}{top} % make part like a chapter
titleformat{part}[display]
    {filleft}
    {MakeUppercase{partname}~thepart}
    {1em}
    {MakeUppercase}

usepackage{titletoc}
titlecontents{part}
    [0em]
    {addvspace{1.5pc}filcenter}
    {- thecontentslabel - }
    {}
    {} % without page number
    [addvspace{.5pc}]

usepackage[hidelinks,linktoc=all]{hyperref}

begin{document}

ttfamily

tableofcontents

part{First part}

end{document}

titlecontents{part}
    [0em]
    {addvspace{1.5pc}filcenter}
    {formattocpart} % numbered
    {} % unnumbered
    {} % filler
    [addvspace{.5pc}]

newcommandformattocpart[1]{%
  colorbox{red!60!green}{%
    begin{tabular}{@{}c@{}}
    - thecontentslabel - 
    #1
    end{tabular}%
  }%
}