From: "trans (Thomas Sawyer)" <transfire@...>
Date: 2012-06-23T00:42:26+09:00
Subject: [ruby-core:45784] [ruby-trunk - Feature #6609] Toplevel as self extended module


Issue #6609 has been updated by trans (Thomas Sawyer).


@nikolai You are correct in part. I'm a big-time supporter of your previous proposal as well. The two don't completely overlap though. Using a self-extended module as top-level object also gives the top-level all the capabilities you would expect from any namespace.

For example, try defining a #method_added callback on top-level.

Or try simply seeing if a constant is defined:

  > Foo = 10
  > const_defined?(:Foo)
  NoMethodError: undefined method `const_defined?' for main:Object

Or removing a method:

  def x; end
  remove_method(:x)
  NoMethodError: undefined method `remove_method' for main:Object

etc.
----------------------------------------
Feature #6609: Toplevel as self extended module
https://bugs.ruby-lang.org/issues/6609#change-27363

Author: trans (Thomas Sawyer)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0


As promised sometime back here is my proposal that Toplevel object become a self-extended module instead of the current partial Object class proxy.

I have written about it in a blog post: http://trans.github.com/2012/06/17/kill-the-proxy-and-save-toplevel.html

In summary the basic idea is to have a special toplevel namespace that is self-extended, e.g.

  module Toplevel
    extend self
  end

in which all toplevel code is evaluated. 

Definitions at the toplevel would no longer inject into Object class. This frees up the toplevel to be used for general purpose DSL "batch" scripting. What I mean by that is that one can create a DSL, load it in to toplevel and then evaluate scripts based on it simply by load/require and without fret that the code loaded in will infect Object if it defines it's own methods.

Conceptually the idea of self-extended module is much simpler than current proxy object --there is really nothing special to understand about it since it is just a module like any other module.

With regard to backward compatibility, the only programs that would be effected are any that defined a toplevel method fully expecting it to add a method to Object. But those will be very rare since it is generally considered bad form to do that. (And of course the simple fix is to wrap the method in the proper `class Object private ... end` code.



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