[Bug] when `tabularray` is loaded, `\cellcolor` doesn't work as expected any more in `\tablenum` cells

[Mo-Gul]

Tell us about the system on which the bug was produced

• up-to-date MiKTeX
• LuaLaTeX

Please outline the bug as you have found it

Hopefully the title says it all. If not, the MWE will.

Share a minimum working example to reproduce the bug

\documentclass[border=1pt, varwidth]{standalone}
\usepackage[table]{xcolor}
\usepackage{booktabs}
\usepackage{tabularray}
\usepackage{siunitx}
\begin{document}

\begin{table}
        \newcommand*{\mc}[1]{\multicolumn{2}{c}{\cellcolor{black!10}#1}}
    \caption{Controlling complex alignment with the \texttt{tablenum} macro.}
        \label{tab:tablenum}
    \begin{tabular}{@{}lr@{}}
            \toprule
        This is a really long Heading & Heading \\
            \midrule
        Info & More info \\
        Info & More info \\
        \mc{12.3} \\
        \mc{333} \\
        \mc{4563} \\
            \bottomrule
    \end{tabular}
\end{table}

\begin{table}
        \newcommand*{\mc}[1]{\multicolumn{2}{c}{\cellcolor{black!10}\tablenum[table-format = 4.1]{#1}}}
    \caption{Controlling complex alignment with the \texttt{tablenum} macro.}
        \label{tab:tablenum}
    \begin{tabular}{@{}lr@{}}
            \toprule
        This is a really long Heading & Heading \\
            \midrule
        Info & More info \\
        Info & More info \\
        \mc{12.3} \\
        \mc{333} \\
        \mc{4563} \\
            \bottomrule
    \end{tabular}
\end{table}

\end{document}

which results in

Comment the tabularray package and it works as expected also for the bottom tabular.

Most likely that is why the same happens in a corresponding tblr environment as well.

[muzimuzhi]

It's a siunitx issue and I've reported to josephwright/siunitx#883.

Here is a modified example which doesn't actually load tabularray but still reproduces the problem:

\documentclass[border=10pt, varwidth]{standalone}
\usepackage[table]{xcolor}
\usepackage{booktabs}
%\usepackage{tabularray}
\usepackage{siunitx}

% pretend tabularray is loaded, to cheat siunitx
\ExplSyntaxOn
\IfPackageLoadedF{tabularray}
  {
    \tl_set:cn { ver@tabularray.sty } { 2025-11-27~... }
    \int_new:N \gTblrLevelInt
  }
\ExplSyntaxOff

\begin{document}

\begin{table}
        \newcommand*{\mc}[1]{\multicolumn{2}{c}{\cellcolor{black!10}#1}}
    \caption{Controlling complex alignment with the \texttt{tablenum} macro.}
        \label{tab:tablenum}
    \begin{tabular}{@{}lr@{}}
            \toprule
        This is a really long Heading & Heading \\
            \midrule
        Info & More info \\
        Info & More info \\
        \mc{12.3} \\
        \mc{333} \\
        \mc{4563} \\
            \bottomrule
    \end{tabular}
\end{table}

\begin{table}
        \newcommand*{\mc}[1]{\multicolumn{2}{c}{\cellcolor{black!10}\tablenum[table-format = 4.1]{#1}}}
    \caption{Controlling complex alignment with the \texttt{tablenum} macro.}
        \label{tab:tablenum}
    \begin{tabular}{@{}lr@{}}
            \toprule
        This is a really long Heading & Heading \\
            \midrule
        Info & More info \\
        Info & More info \\
        \mc{12.3} \\
        \mc{333} \\
        \mc{4563} \\
            \bottomrule
    \end{tabular}
\end{table}

\end{document}