LaTeX: local class options

clsopts.sty

%%
%% This is file 'clsopts.sty'.
%%
%% Copyright 2019 Takuto ASAKURA (wtsnjp)
%%   GitHub:   https://github.com/wtsnjp
%%   Twitter:  @wtsnjp
%%
%% This package is distributed under the MIT License.
%%

%% package declaration
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{clsopts}[2019/12/12 v0.1.0]
\RequirePackage{etoolbox}

%% preparations
\def\clop@pkgname{clsopts}
\def\clop@warn{\PackageWarningNoLine\clop@pkgname}

%--------------------------------------- register local class options

\def\clop@list{}
\def\clop@register#1{\edef\clop@list{#1,\clop@list}}

\DeclareOption*{\clop@register{\CurrentOption}}
\ProcessOptions\relax

%--------------------------------------- patches

\newif\ifclop@clsopt

\patchcmd{\@fileswith@pti@ns}
  {%
    \ifx#1\@clsextension
      \ifx\@classoptionslist\relax
        \xdef\@classoptionslist{\zap@space#2 \@empty}%
        \def\reserved@a{%
          \@onefilewithoptions#3[{#2}][{#4}]#1%
          \@documentclasshook}%
      \else
        \def\reserved@a{%
          \@onefilewithoptions#3[{#2}][{#4}]#1}%
      \fi
    \else
  }
  {%
    \ifx#1\@clsextension
      \ifx\@classoptionslist\relax
        \edef\@classoptionslist{\zap@space#2 \@empty}%
        \def\clop@classoptionslist{}%
        \@for\clop@cur@opt:=\@classoptionslist\do{%
          \clop@clsoptfalse
          \@for\clop@lopt:=\clop@list\do{%
            \ifx\clop@cur@opt\clop@lopt
              \clop@clsopttrue
            \fi}
          \ifclop@clsopt\else
            \edef\clop@classoptionslist{\clop@cur@opt,\clop@classoptionslist}%
          \fi}%
        \global\let\@classoptionslist\clop@classoptionslist
        \def\reserved@a{%
          \@onefilewithoptions#3[{\clop@list#2}][{#4}]#1%
          \@documentclasshook}%
      \else
        \def\reserved@a{%
          \@onefilewithoptions#3[{\clop@list#2}][{#4}]#1}%
      \fi
    \else
  }
  {\relax}{\clop@warn{Failed to patch the LaTeX kernel}}

%--------------------------------------- all done
\endinput
%% EOF

test.tex

%#!pdflatex
\RequirePackage[draft,fleqn]{clsopts}  % draft,fleqn: only for the class
\documentclass[a4paper,12pt]{article}  % a4paper,12pt: for both the class and packages
\usepackage{hyperref}

\makeatletter
\parindent=0pt
\edef\clsopts{\ifx\@classoptionslist\relax EMPTY\else\@classoptionslist\fi}
\makeatother

\begin{document}

\hbox to\textwidth{\hskip\textwidth Hello!}

\[
E=mc^2
\]

\href{https://google.com}{Google}

Global options: \clsopts

\end{document}