Tcolorbox rule width with table inside

Question

Apparently, the boxrule command has not effect with an enhanced tcolorbox having a tabularx inside.

How can I specify the width of the frame arount the tabularx ?

Here is the MWE :

\documentclass{article}
\usepackage[skins]{tcolorbox}
\usepackage{array,tabularx}
\usepackage{colortbl}
\begin{document}

% \usepackage{array,tabularx}
% \usepackage{colortbl} - or - \usepackage[table]{xcolor}
\tcbset{enhanced,fonttitle=\bfseries\large,fontupper=\normalsize\sffamily,
    colback=yellow!10!white,colframe=red!50!black,colbacktitle=red!30!white,
    coltitle=black,center title,
    boxrule=10pt, % NO EFFECT
}
\begin{tcolorbox}[tabularx*={\arrayrulewidth0.5mm}{X|X|X},title=My table]
    One
    & Two
    & Three \\\hline\hline
    1000.00 & 2000.00 & 3000.00\\\hline
    2000.00 & 3000.00 & 4000.00
\end{tcolorbox}

% EDIT : with a multicolumn as 1st cell this does not compile anymore
\begin{tcolorbox}[boxrule=2pt,tabularx*={\arrayrulewidth2pt}{YY|YY|YY},
    title=My table
    ]
    \multicolumn{2}{c|}{title}
    &   \multicolumn{2}{c|}{title}
    &   \multicolumn{2}{c}{title} \\\hline
    2 & d & 3 & e & 4 & f \\\hline
    title & \multicolumn{3}{|l|}{h} & \multicolumn{1}{c|}{title} & j \\
\end{tcolorbox}

\end{document}

EDIT : the first answer is alright for the 1st table in the MWE, but I'm using a multicolumn as 1st cell and this brings an Misplaces \omit error. MWE has been modified with the problematic table.

Answer 1

The definition of the tabularx style has as setting for the boxrule to be 0.5mm. You can overwrite the setting by copying the style from the source and removing this part:

\documentclass{article}
\usepackage[skins]{tcolorbox}
\usepackage{array,tabularx}
\usepackage{colortbl}
\begin{document}

% \usepackage{array,tabularx}
% \usepackage{colortbl} - or - \usepackage[table]{xcolor}
\tcbset{enhanced,fonttitle=\bfseries\large,fontupper=\normalsize\sffamily,
    colback=yellow!10!white,colframe=red!50!black,colbacktitle=red!30!white,
    coltitle=black,center title,
    boxrule=10pt, % NO EFFECT
}
\makeatletter
\tcbset{tabularx*/.style 2 args={%
    boxsep=\z@,top=\z@,bottom=\z@,leftupper=\z@,rightupper=\z@,
    toptitle=1mm,bottomtitle=1mm,% boxrule setting here removed
    before upper={\arrayrulecolor{tcbcol@frame}\def\arraystretch{1.1}#1%
      \tcb@hack@currenvir\tabularx{\linewidth}{#2}},
    after upper=\endtabularx\arrayrulecolor{black}}}
\makeatother
\begin{tcolorbox}[tabularx*={\arrayrulewidth0.5mm}{X|X|X},title=My table]
    One
    & Two
    & Three \\\hline\hline
    1000.00 & 2000.00 & 3000.00\\\hline
    2000.00 & 3000.00 & 4000.00
\end{tcolorbox}
\end{document}

Result:

Edit: in more recent versions of tcolorbox the definition is slightly changed. In that case the new definition should be as follows:

\tcbset{tabularx*/.style 2 args={%
    boxsep=\z@,top=\z@,bottom=\z@,leftupper=\z@,rightupper=\z@,
    toptitle=1mm,bottomtitle=1mm,
    before upper*={%
      \let\tcb@CT@arc@save\CT@arc@%
      \arrayrulecolor{tcbcolframe}\def\arraystretch{1.1}#1%
      \tcb@hack@currenvir\tabularx{\linewidth}{#2}},
    after upper*={\endtabularx\global\let\CT@arc@\tcb@CT@arc@save}%
  }
}

Answer 2

If the need is to change value of boxrule specified by option tabularx*, then tabularx*/.append style={boxrule=<dimen>} is simpler, in which.append style is one of predefined pgfkeys handlers.

Full example:

\documentclass{article}
\usepackage[skins]{tcolorbox}
\usepackage{array,tabularx}
\usepackage{colortbl}

\tcbset{
    enhanced,
    fonttitle=\bfseries\large,
    fontupper=\normalsize\sffamily,
    colback=yellow!10!white,
    colframe=red!50!black,
    colbacktitle=red!30!white,
    coltitle=black,
    center title,
    % change boxrule set by "tabularx*", by default it's 0.5mm
    tabularx*/.append style={boxrule=10pt}
}

\begin{document}
\begin{tcolorbox}[tabularx*={\arrayrulewidth0.5mm}{X|X|X}, title=My table]
    One
    & Two
    & Three \\\hline\hline
    1000.00 & 2000.00 & 3000.00\\\hline
    2000.00 & 3000.00 & 4000.00
\end{tcolorbox}
\end{document}

Update

Just for fun. Here a new pgfkeys handler .patch code={<search>}{<replace>} which internally used \xpatchcmd from xpatch package, is defined.

\documentclass{article}
\usepackage{tcolorbox}
\usepackage{xpatch}

\usepackage{array,tabularx}
\usepackage{colortbl}

\makeatletter
% usage:
%   <key>/.patch code={search}{replace}
% similar to def of /handlers/.add code/.code 2 args={...}
\pgfkeys{/handlers/.patch/.code 2 args=%
  % Find out, whether with args or not.
  \pgfkeysifdefined{\pgfkeyscurrentpath/.@args}%
  {% Yes, so add to body and reuse args
    \pgfkeyspatchvalue{\pgfkeyscurrentpath/.@body}{#1}{#2}%
    % Redefine code
    {%
      \pgfkeysgetvalue{\pgfkeyscurrentpath/.@args}{\pgfkeys@tempargs}%
      \pgfkeysgetvalue{\pgfkeyscurrentpath/.@body}{\pgfkeys@tempbody}%
      \def\pgfkeys@marshal{\expandafter\gdef\expandafter\pgfkeys@global@temp\pgfkeys@tempargs}%
      \expandafter\pgfkeys@marshal\expandafter{\pgfkeys@tempbody}%
    }%
    \pgfkeysifdefined{\pgfkeyscurrentpath/.@@body}{%
      % support for \pgfkeysndefargs:
      \pgfkeyslet{\pgfkeyscurrentpath/.@@body}{\pgfkeys@global@temp}%
    }{%
      % support for \pgfkeysdefargs:
      \pgfkeyslet{\pgfkeyscurrentpath/.@cmd}{\pgfkeys@global@temp}%
    }%
  }{% No, so single argument (simple \pgfkeysdef). Redefine accordingly.
    \edef\pgf@expanded@path{\pgfkeyscurrentpath}%
    {%
      \pgfkeysifdefined{\pgf@expanded@path/.@cmd}{%
        \expandafter\expandafter\expandafter\pgfkeys@temptoks
        \expandafter\expandafter\expandafter{%
        \csname pgfk@\pgf@expanded@path/.@body\endcsname}%
      }{%
        \expandafter\pgfkeys@temptoks\expandafter{%
        \expandafter\pgfkeyssetvalue\expandafter{\pgf@expanded@path}{##1}}%
      }%
      \edef\pgfkeys@temp{\the\pgfkeys@temptoks}%
      \pgfkeyspatchvalue\pgfkeys@temp{#1}{#2}%
      \global\let\pgfkeys@global@temp\pgfkeys@temp
    }%
    \def\pgf@temp{\pgfkeyssetvalue{\pgf@expanded@path/.@body}}%
    \expandafter\pgf@temp\expandafter{\pgfkeys@global@temp}%
    \expandafter\long\expandafter\def\expandafter\pgfkeys@temp\expandafter##\expandafter1\expandafter\pgfeov\expandafter{\pgfkeys@global@temp}%
    \pgfkeyslet{\pgf@expanded@path/.@cmd}\pgfkeys@temp
  }%  
}

% usage:
%   \pgfkeyspatchvalue{<key>}{<search>}{<replace>}
% similar to \pgfkeysaddvalue
\long\def\pgfkeyspatchvalue#1#2#3{%
  \pgfkeysifdefined{#1}{%
    \expandafter\xpatchcmd\csname pgfk@#1\endcsname{#2}{#3}{}
      {\PackageError{pgfkeys}{Patching for key #1 fails}}%
  }{}%
}
\makeatother


\begin{document}

\tcbset{
  colframe=black!25,
  colbacktitle=black!75
}

\begin{tcolorbox}[boxrule=5pt, tabularx*={\arrayrulewidth0.5mm}{X|X|X}, title=Before patching]
  One     & Two     & Three   \\ \hline\hline
  1000.00 & 2000.00 & 3000.00 \\ \hline
  2000.00 & 3000.00 & 4000.00
\end{tcolorbox}

% patch option "tabularx*", remove "boxrule=0.5mm"
\tcbset{
  tabularx*/.patch={boxrule=0.5mm}{}
}

\begin{tcolorbox}[boxrule=5pt, tabularx*={\arrayrulewidth0.5mm}{X|X|X}, title=After patching]
  One     & Two     & Three   \\ \hline\hline
  1000.00 & 2000.00 & 3000.00 \\ \hline
  2000.00 & 3000.00 & 4000.00
\end{tcolorbox}

\end{document}