Expand conditional in the outer specification for a tabularray table

Question

I am trying to create a custom tblr environment for a schedule which I reuse often. I want to include an optional label for cross-referencing.

I'm using the xparse \NewDocumentEnvironment command together with tabularray, but I cannot get tabularray to expand the command \IfValueT{#1}{label={#1},} in the outer specification.

Everything works if I instead use \IfValueTF and duplicate the \begin{tblr}[, but that doesn't seem very robust.

Is there a way to make the "testa" option in the below MWE work?

MWE:

\documentclass{scrreprt}

\usepackage{tabularray}

\NewDocumentEnvironment{testa}{o m +b}{
\begin{tblr}[
    \IfValueT{#1}{label={#1},}
    caption={#2},
    long,
]{
    colspec = {ll},
}
    Column 1 & Column 2 \\
    #3
\end{tblr}
}{}


\NewDocumentEnvironment{testb}{o m +b}{
\IfValueTF{#1}{\begin{tblr}[label={#1},}{\begin{tblr}[}
    caption={#2},
    long,
]{
    colspec = {ll},
}
    Column 1 & Column 2 \\
    #3
\end{tblr}
}{}



\begin{document}

\begin{testa}[labela]{captiona}
    a & b
\end{testa}

\begin{testb}[labelb]{captionb}
    a & b
\end{testb}

Tables \ref{labela} and \ref{labelb} should be the same, but Table \ref{labela} is an undefined reference.

\end{document}

Answer 1

I would set the option outside of the table:

\documentclass{scrreprt}

\usepackage{tabularray}

\NewDocumentEnvironment{testa}{o m +b}{%
\IfValueT{#1}{\SetTblrOuter{label={#1}}}%
\begin{tblr}[
    caption={#2},
    long,
]{
    colspec = {ll},
}
    Column 1 & Column 2 \\
    #3
\end{tblr}
}{}




\begin{document}

\begin{testa}[labela]{captiona}
    a & b
\end{testa}


Tables \ref{labela} 

\end{document}

Answer 2

You could go with

\documentclass{scrreprt}

\usepackage{tabularray}

\NewDocumentEnvironment{testa}{o m +b}{%
  \expanded{\noexpand\begin{tblr}[
    \IfValueT{#1}{label={#1},}}
    caption={#2},
    long,
]{
    colspec = {ll},
}
    Column 1 & Column 2 \\
    #3
\end{tblr}%
}{}

\begin{document}

\begin{testa}[labela]{captiona}
    a & b
\end{testa}

\end{document}

A cleaner version:

\documentclass{scrreprt}

\usepackage{tabularray}

\ExplSyntaxOn
\NewDocumentCommand{\testastart}{mm}
 {
  \jw_testastart:en { \tl_if_novalue:nF { #1 } { label={#1} } } { #2 }
 }
\cs_new_protected:Nn \jw_testastart:nn
 {
  \begin{tblr}[#1, caption={#2},long]
 }
\cs_generate_variant:Nn \jw_testastart:nn { e }
\ExplSyntaxOff

\NewDocumentEnvironment{testa}{o m +b}{%
    \testastart{#1}{#2}{
    colspec = {ll},
}
    Column 1 & Column 2 \\
    #3
\end{tblr}%
}{}

\begin{document}

\begin{testa}[labela]{captiona}
    a & b
\end{testa}

\end{document}

The .aux file

\relax 
\providecommand*\new@tpo@label[2]{}
\newlabel{labela}{{1}{1}{}{}{}}
\@writefile{lot}{\contentsline {table}{\numberline {1}{captiona}}{1}{}\protected@file@percent }
\gdef \@abspage@last{1}