From: "eLobato (Daniel Lobato Garcia)" <elobatocs@...>
Date: 2013-05-12T17:41:34+09:00
Subject: [ruby-core:54927] [ruby-trunk - Feature #8393] A class who's parent class is in a module can go wrong if files are required in the wrong order


Issue #8393 has been updated by eLobato (Daniel Lobato Garcia).


jeremyevans0: That's what I did when I found a problem caused by this on production code. Nonetheless you have to take into account that sometimes the order of the requires is not something you control. 

nobu: In order to get these results, create the files, open IRB and run:

> require 'animal.rb'
> require 'dog.rb'
> require 'bark.rb'

> Bark::Dog.new.bark
fuck.        <--- This should be woof because Bark::Dog should inherit from Bark::Animal.

Let me know if I am missing anything.
----------------------------------------
Feature #8393: A class who's parent class is in a module can go wrong if files are required in the wrong order
https://bugs.ruby-lang.org/issues/8393#change-39268

Author: eLobato (Daniel Lobato Garcia)
Status: Feedback
Priority: Normal
Assignee: 
Category: 
Target version: 


Hi,

I have found that inheritance is not done properly in a certain case. Let's say we have the following files:

--------------
animal.rb -

class Animal
  def bark
    puts 'fuck.'
  end
end
 

dog.rb -

module Bark
  class Dog < Animal
  end
end


bark.rb - 

module Bark
  class Animal
    def bark
      puts 'woof'
    end
  end
end
------------

If these files are required in that order (or any order where Bark::Animal is not required before Animal), Bark::Dog.new.bark will output "fuck.", showing the inheritance was done wrong, because in the case that there are two classes from which it can inherit (Animal and Bark::Animal), it should inherit from the class inside its module (Bark).

A workaround for this is defining Dog as Dog < Bark::Animal, that forces Dog to use the correct Animal class. 

I found this on the latest 1.8.7, 1.9.2, 1.9.3 and 2.0.0dev, both using rvm and without using it. I could not find information about this on the issue tracker or on Google.

In my opinion a way to fix this is to check when a file is required if any of our current files could inherit from something in a module of the file that is imported, but that looks like it can be complicated with nested modules, etc.. so I'm all ears for better design decisions. 

I would like to fix this myself as my first Ruby core contribution, but I was unsure if this is an actual bug. To me it looks like this behavior is totally unexpected, let me know if anything is wrong here.

Thanks!



-- 
http://bugs.ruby-lang.org/