How to make colspec allow variables?

[note286]

My requirement is how to get colspec to receive variable values. Here is my exploration process.

\documentclass{article}
\usepackage{tabularray}
\begin{document}
\begin{tblr}{colspec={r|X}}
AAAAAA & Lorem\ ipsum\ dolor\ sit\ amet,\ consectetur\ adipisicing\ elit,\ sed\ do\ eiusmod\ tempor \\
AAA & BBB \\
\end{tblr}
\end{document}

As shown above, everything is normal.

I found the function \__tblr_parse_colrow_spec:nn { column } { } by reading the source code, and I tried to configure the column options by calling the function \__tblr_parse_colrow_spec:nn { column } { } directly.

\documentclass{article}
\usepackage{tabularray}
\begin{document}
\ExplSyntaxOn
\begin{tblr}{}
\__tblr_parse_colrow_spec:nn { column } { r|X }
AAAAAA & Lorem\ ipsum\ dolor\ sit\ amet,\ consectetur\ adipisicing\ elit,\ sed\ do\ eiusmod\ tempor \\
AAA & BBB \\
\end{tblr}
\ExplSyntaxOff
\end{document}

But I got the following results. The vertical bar is not displayed correctly. What causes this?

Then, I directly modify the tabularray.sty file to generate variant function to the function \__tblr_parse_colrow_spec:nn so as to receive variables.

\cs_generate_variant:Nn \__tblr_parse_colrow_spec:nn { nV }

And modified the function corresponding to colspec parameter.

% colspec .code:n = \__tblr_parse_colrow_spec:nn { column } {#1},
colspec .code:n = \__tblr_parse_colrow_spec:nV { column } {#1},

Then we run the following example:

\documentclass{article}
\usepackage{tabularray}
\begin{document}
\ExplSyntaxOn
\tl_new:N \l_tmp_colspec_tl
\tl_set:Nn \l_tmp_colspec_tl { r|X }
\begin{tblr}{colspec=\l_tmp_colspec_tl}
AAAAAA & Lorem\ ipsum\ dolor\ sit\ amet,\ consectetur\ adipisicing\ elit,\ sed\ do\ eiusmod\ tempor \\
AAA & BBB \\
\end{tblr}
\ExplSyntaxOff
\end{document}

We got the expected result.

In conclusion, my purpose is to use variables to configure column options. If the first example works correctly, then I can pass the variable to the variant function without modifying the .sty file. At present, I can't find a suitable way to meet my needs.

[lvjr]

It is better to define a new environment, because you can do anything you want without modifying private functions in the package:

\documentclass{article}
\usepackage{tabularray}
\begin{document}
\ExplSyntaxOn

\tl_new:N \l__mytest_keyval_tl

\keys_define:nn {mytest}
  {
    colspec .code:n = \__mytest_store_keyval:no { colspec } {#1},
    unknown .code:n = \__mytest_store_keyval:Vn \l_keys_key_str {#1},
  }
\cs_new_protected:Npn \__mytest_store_keyval:nn #1 #2
  {
    \tl_if_empty:nTF {#2}
      { \tl_put_right:Nn \l__mytest_keyval_tl {#1,} }
      { \tl_put_right:Nn \l__mytest_keyval_tl {#1 = {#2},} }      
  }
\cs_generate_variant:Nn \__mytest_store_keyval:nn {no,Vn}

\NewDocumentEnvironment {mytblr} {O{} m +b}
  {
    \tl_clear:N \l__mytest_keyval_tl
    \keys_set:nn {mytest} {#2}
    \tl_set:Nx \l_tmpa_tl
      {
        \exp_not:n {\begin{tblr}[#1]} {\exp_not:V \l__mytest_keyval_tl}
          \exp_not:n {#3}
        \exp_not:n {\end{tblr}}
      }
    \tl_use:N \l_tmpa_tl
  } {}

\tl_new:N \l_tmp_colspec_tl
\tl_set:Nn \l_tmp_colspec_tl { r|X }

\begin{mytblr}{colspec=\l_tmp_colspec_tl,hlines,rowsep=1pt}
AAAAAA & Lorem\ ipsum\ dolor\ sit\ amet,\ consectetur\ adipisicing\ elit,\ sed\ do\ eiusmod\ tempor \\
AAA & BBB \\
\end{mytblr}

\ExplSyntaxOff
\end{document}

[note286]

Thank you very much for your answer, which completely solved my problem.
In addition, I would like to ask why direct use of \__tblr_parse_colrow_spec:nn { column } { r|X } can't get the expected effect? As shown in the second example in the question.

[lvjr]

From the manual: "All commands which change the specifications of tables must be defined with \NewTableCommand.

\documentclass{article}
\usepackage{tabularray}
\begin{document}
\ExplSyntaxOn
\NewTableCommand \mycolspec [1] {\__tblr_parse_colrow_spec:nn { column } { #1 } }
\begin{tblr}{}
\mycolspec{ r|X }
AAAAAA & Lorem\ ipsum\ dolor\ sit\ amet,\ consectetur\ adipisicing\ elit,\ sed\ do\ eiusmod\ tempor \\
AAA & BBB \\
\end{tblr}
\ExplSyntaxOff
\end{document}

But it is always dangerous to use private functions such as \__tblr_parse_colrow_spec:nn in your package. If you use them the documents of your users may break down in the future. Therefore it is better to keep your package away from them.

[note286]

Thank you very much for your answer.