alias_method_chain_resilient.rb

module AliasMethodChainResilient
  # Give us a module which will intercept attempts to alias methods named in
  # the keys of method_aliases, and instead alias the methods named in the
  # values of method_aliases.
  def self.alias_intercepting_module(method_aliases)
    Module.new do
      define_method :alias_method do |new_name, old_name|
        if method_aliases.key?(old_name.to_sym)
          super new_name, method_aliases[old_name.to_sym]
        else
          super new_name, old_name
        end
      end
    end
  end

  def prepend_features(base)
    method_aliases = instance_methods.each_with_object({}) do |method_name, aliases|
      aliases[method_name] = :"__#{method_name}_before_#{self.name}"
      base.send :alias_method, aliases[method_name], method_name
    end

    base.singleton_class.send :prepend, AliasMethodChainResilient.alias_intercepting_module(method_aliases)
    super
  end
end


module M
  # Without this, we'll get a NoMethodError in Ruby 2.0, and a SystemStackError
  # in 2.1. With it, things work as expected.
  extend AliasMethodChainResilient

  def do_it
    puts "M"
    super
  end
end

class C
  def do_it
    puts 'C'
  end

  prepend M

  def do_it_with_amc
    puts 'amc'
    do_it_without_amc
  end

  alias_method :do_it_without_amc, :do_it
  alias_method :do_it, :do_it_with_amc
end

C.new.do_it

# Output, with AliasMethodChainResilient
# M
# amc
# C