\AtEndOfPackage{\RequirePackage{hoge}} の困ったエラーをなんとかするアレ

20160916-AtEndOfPackage-RequirePackage-test.tex

%%% Code updated (2016-09-16 19:02 GMT+09:00)

\begin{filecontents}{test.sty}
\DeclareOption{TEST}{\typeout{*** TEST OPTION ***}}
\ProcessOptions
\AtEndOfPackage{\RequirePackage{xspace}} % some package without \ProcessOptions
\end{filecontents}

% !!! TeX code BEGIN
\makeatletter
\def\@process@pti@ns{%
  \@for\CurrentOption:=\@curroptions\do{%
    \@ifundefined{ds@\CurrentOption}%
      {\@use@ption
       \default@ds}%
      \@use@ption}%
  \@for\CurrentOption:=\@declaredoptions\do{%
    \expandafter\let\csname ds@\CurrentOption\endcsname\relax}%
  \let\CurrentOption\@empty
  \let\@fileswith@pti@ns\@@fileswith@pti@ns
  \AtEndOfPackage{%
    \expandafter\let\csname @unprocessedoptions-\@currname.\@currext\endcsname % !!!
              \relax}}
\def\RequirePackageWithOptions{%
  \AtEndOfPackage{%
    \expandafter\let\csname @unprocessedoptions-\@currname.\@currext\endcsname % !!!
              \relax}%
  \@loadwithoptions\@pkgextension\RequirePackage}
\def\@onefilewithoptions#1[#2][#3]#4{%
  \@pushfilename
  \xdef\@currname{#1}%
  \global\let\@currext#4%
  \expandafter\let\csname\@currname.\@currext-h@@k\endcsname\@empty
  \let\CurrentOption\@empty
  \@reset@ptions
  \makeatletter
  \def\reserved@a{%
    \@ifl@aded\@currext{#1}%
      {\@if@ptions\@currext{#1}{#2}{}%
        {\@latex@error
            {Option clash for \@cls@pkg\space #1}%
            {The package #1 has already been loaded
             with options:\MessageBreak
             \space\space[\@ptionlist{#1.\@currext}]\MessageBreak
             There has now been an attempt to load it
              with options\MessageBreak
             \space\space[#2]\MessageBreak
             Adding the global options:\MessageBreak
             \space\space
                  \@ptionlist{#1.\@currext},#2\MessageBreak
             to your \noexpand\documentclass declaration may fix this.%
             \MessageBreak
             Try typing \space <return> \space to proceed.}}}%
      {\@pass@ptions\@currext{#2}{#1}%
       \global\expandafter
       \let\csname ver@\@currname.\@currext\endcsname\@empty
       \InputIfFileExists
         {\@currname.\@currext}%
         {}%
         {\@missingfileerror\@currname\@currext}%
    \expandafter\let\csname @unprocessedoptions-\@currname.\@currext\endcsname % !!!
              \@@unprocessedoptions
    \csname\@currname.\@currext-h@@k\endcsname
    \expandafter\let\csname\@currname.\@currext-h@@k\endcsname
              \@undefined
    \ifx\@unprocessedoptions\relax      %%% !!! If the package has redefined to \relax
      \let\@unprocessedoptions\@undefined % !!! then, no error should appear; re-initialization only
    \else                               %%% !!!
      \csname @unprocessedoptions-\@currname.\@currext\endcsname               % !!!
    \fi                                 %%% !!!
    \expandafter\let\csname @unprocessedoptions-\@currname.\@currext\endcsname % !!!
              \@undefined}                                                     % !!!
    \@ifl@ter\@currext{#1}{#3}{}%
      {\@latex@warning@no@line
         {You have requested,\on@line,
          version\MessageBreak
            `#3' of \@cls@pkg\space #1,\MessageBreak
          but only version\MessageBreak
           `\csname ver@#1.\@currext\endcsname'\MessageBreak
          is available}}%
    \ifx\@currext\@clsextension\let\LoadClass\@twoloadclasserror\fi
    \@popfilename
    \@reset@ptions}%
  \reserved@a}
\let\@unprocessedoptions\@undefined     %%% !!! Initially \@undefined; kernel won't use it
\makeatother
% !!! TeX code END

\documentclass{article}
\usepackage[TEST]{test}
\begin{document}
success!
\end{document}

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