alias xxx_original_require require みたいなことをしても済むように作った

original.rb

class Module

  def original method

    original_methods = Hash.new do |original_methods, method|
      original_methods[method.to_sym] = original_method = []
      define_method :"original_#{method.to_sym}" do |*args, &blk|
        fail if original_method.empty?
        tmp = original_method.pop
        res = tmp.call *args, &blk
        original_method.push tmp
        res
      end
      original_method
    end

    define_method :original do |method|

      original_methods[method.to_sym].push self.method(method.to_sym)

    end

    original method

  end

  def override method, &definition

    original method
    define_method method, &definition

  end

end

module Test

  extend self 

  def hello
    puts "hello"
  end

  original :hello

  def hello
    original_hello
    puts "also"
  end

  original :hello

  def hello
    original_hello
    puts "oooooo"
  end

  override :hello do
    original_hello
    puts "aaaa"
  end

end

Test.hello
# stdout
# hello
# also
# oooooo
# aaaa


module Kernel

  original :require # => ただしこれがなぜかSystemStackErrorになる

  def require path
    puts "override require!"
    original_require path
  end

end