TeX：和文文字トークンの和文カテゴリコードの値を展開限定文脈で取得する

tckcatvalue.sty

%% package declaration
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{tckcatvalue}[2019/10/31 v0.1]
\def\xx@pkgname{tckcatvalue}

%% engine
\chardef\xx@uptex=\ifx\enablecjktoken\@undefined 0 \else 1 \fi

%% inspect the type and set it to \xx@type
% 1 = upTeX, old pTeX
% 0 = new pTeX
\begingroup
  \ifnum\xx@uptex=1 \forcecjktoken \fi
  \kcatcode`☆=16
  \let\xx@tok=☆
  \kcatcode`☆=18 \kcatcode`漢=16
  \global\chardef\xx@type=\ifcat 漢\xx@tok 1 \else 0 \fi
\endgroup

\PackageWarningNoLine\xx@pkgname
 {type = \number\xx@type}

%%<*> \kcatvalue{<ja-char>}
\newcommand*\kcatvalue[1]{%
  \number\xx@kcat@value#1\space}

\ifnum\xx@type=\@ne     %-----<*type=1>

  \begingroup
    \ifnum\xx@uptex=1 \forcecjktoken \fi
    \kcatcode`漢=16 \global\let\xx@A=漢
    \kcatcode`あ=17 \global\let\xx@B=あ
    \kcatcode`☆=18 \global\let\xx@C=☆
    \ifnum\xx@uptex=1
      \kcatcode`＃=19 \global\let\xx@D=＃ % hangul
    \else \global\let\xx@D\xx@A % never-matching
    \fi
    %% \xx@kcat@value{<ja-char>}
    \gdef\xx@kcat@value#1{%
      % comapre with prepared ja-char tokens
      \ifcat     \noexpand#1\xx@A 16%
      \else\ifcat\noexpand#1\xx@B 17%
      \else\ifcat\noexpand#1\xx@C 18%
      \else\ifcat\noexpand#1\xx@D 19%
      \else 0%
      \fi\fi\fi\fi}
  \endgroup

\else                   %-----<*type=0>

  \begingroup
    \escapechar\m@ne
    %% \xx@kcat@value{<ja-char>}
    \edef\xx@args{{\string\kanj}{\string\ter}}
    \def\xx@next#1#2{%
      \gdef\xx@kcat@value##1{%
        \ifcat\relax\noexpand##10% avoid complex things
        \else \expandafter\xx@kcat@value@a\meaning##1#1@%
        \fi}%
      % force the ja-char to be explicit through \meaning,
      % then inspect the \kcatcode parameter value for the ja-char
      \gdef\xx@kcat@value@a##1#1##2@{%
        \ifcat @##1@\xx@kcat@value@b##2@%
        \else 0\fi}%
      \gdef\xx@kcat@value@b##1#2 ##2##3@{%
        \kcatcode`##2\space}%
    }\expandafter\xx@next\xx@args
  \endgroup

\fi                     %-----</type>

%% done
\endinput

test-tckcatvalue.tex

\documentclass{article}
\usepackage{tckcatvalue}
\makeatletter %!!!!!!!!!!!!!!!!!!!!!!!!! TeX code BEGIN
\ifx\ucs\@undefined\else \enablecjktoken \fi
\kcatcode`◎=17
\kcatcode`Я=17
\let\◎=◎
\def\Я{Я}

\kcatcode`字=16
\kcatcode`ア=17
\kcatcode`◎=18
\kcatcode`Я=18
\kcatcode`あ=18 % wow!                            up new-p old-p
\tracingmacros=1 \tracingonline=1
\typeout{1:字:\kcatvalue 字.}                   %  16   16    16
\tracingmacros=0 \tracingonline=0
\typeout{2:ア:\kcatvalue ア.}                   %  17   17    17
\typeout{3:◎:\kcatvalue ◎.}                   %  18   18    18
\typeout{4:Я:\kcatvalue Я.}                     %  18   18    18
\typeout{5:\string\◎:\kcatvalue\◎.}           %  17   18    17
\typeout{6:\string\Я:\expandafter\kcatvalue\Я.} %  17   18    18

\stop