fucked_up_inheritance.rb

module V1A
  def mpla
    "#{foo} from mpla"
  end

  def foo
    return 'from V1'
  end
end

module V2A
  include V1A

  def foo
    return 'from V2'
  end
end

module V1
  class A
    include V1A
  end

  class B < A
    def bar
      "B #{mpla}"
    end
  end

  class C < A
    def bar
      "C #{mpla}"
    end
  end
end

module V2
  include V1

  class A
    include V2A
  end

  class B < A
    def bar
      "B ~ #{mpla}"
    end
  end

  class C < V1::C
    include V2A
  end
end

puts V1::B.new.bar #=> B from V1 from mpla
puts V2::B.new.bar #=> B ~ from V2 from mpla
puts V1::C.new.bar #=> C from V1 from mpla
puts V2::C.new.bar #=> C from V2 from mpla

p V1::B.ancestors #=> [V1::B, V1::A, V1A, Object, Kernel, BasicObject]
p V2::B.ancestors #=> [V2::B, V2::A, V2A, V1A, Object, Kernel, BasicObject]
p V1::C.ancestors #=> [V1::C, V1::A, V1A, Object, Kernel, BasicObject]
p V2::C.ancestors #=> [V2::C, V2A, V1::C, V1::A, V1A, Object, Kernel, BasicObject]