How to avoid "overfull" warnings with tcblistings and parskip package?

Question

Consider the following MWE:

\documentclass{article}
\usepackage{lipsum}
\usepackage{tcolorbox}
%%% this two following packages are used in the format I have to use
\usepackage[parfill]{parskip}

\begin{document}
\lipsum[1]

\begin{tcolorbox}
     checking content
\end{tcolorbox}

\lipsum[1]
\end{document}

it compiles well, with correctly aligned boxes, but it gives a

mwe-tcbox.tex|12 warning| Overfull \hbox (30.0pt too wide) in paragraph at lines 12--12

I tried the tcbset trick adapted from this answer, but it does not work; the line

\tcbset{before app=\parfillskip0pt}

(adding [hooks] to the tcolorbox package) is silent, but does not solve the warning.

If I remove the \usepackage[parfill]{parskip} from the code all is well --- but I really can't do that, because it is in the format I have to use for this document. I can hack it with something like width=0.9\linewidth in the options of the tcolorbox, but well --- It's a hack.

I also could manage to silence the warnings using the silence package --- but again, this will also shut off real warnings.

Can I avoid the warning and still using the full textwidth for the color boxes?

Answer 1

The parfill option to the parskip package sets \parfillskip to 30pt plus 1fil, in order to avoid the final line of a paragraph to end (almost) flush with the right margin: no wonder you get an overfull line by exactly 30pt.

Redefine the parskip style to issue \parfillskip=0pt:

\documentclass[draft]{article}
\usepackage{lipsum}
\usepackage{tcolorbox}

%%% this two following packages are used in the format I have to use
\usepackage[parfill]{parskip}

\tcbset{
  parskip/.style={
    before={\par\pagebreak[0]\parindent=0pt},
    after={\parfillskip=0pt\par},
  },
}

\begin{document}

\lipsum[1]

\begin{tcolorbox}
     checking content
\end{tcolorbox}

\lipsum[1]

\the\parfillskip

\end{document}

I added \the\parfillskip to show it's correctly reset and also the draft option to prove there's no overfull box.