Issue #6609 has been updated by drbrain (Eric Hodel).


trans (Thomas Sawyer) wrote:
> As promised sometime back here is my proposal that Toplevel object become a self-extended module instead of the current partial Object class proxy.

What is a "partial Object class proxy"? It does not seem to exist. The top-level object (rb_vm_top_self) is an instance of Object where to_s is overridden to return "main" (see Init_top_self in vm.c).

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

This post has the misconception that the top-level object is somehow special.

Of course you cannot call define_method at top-level.  self is not a Module subclass, it's an Object instance:

  $ ruby -e 'p self.class.ancestors'
  [Object, Kernel, BasicObject]

Of course methods defined at the top-level affect every other object. That's exactly how it works everywhere else:

  $ cat t.rb 
  class C
    def initialize name
      @name = name
    end
  
    def make
      def name
        @name
      end
    end
  end
  
  c1 = C.new :c1
  c2 = C.new :c2
  
  c2.name rescue puts "c2.name not defined"
  
  c1.make
  
  p c1.name
  p c2.name
  
  $ ruby t.rb
  c2.name not defined
  :c1
  :c2

> 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.

Since you are adding more things it seems more complicated.  There are no extra things in the current top-level object.  It's so simple it can be literally described as "the top-level object".

> 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.

Such a change would break this:

https://github.com/xml4r/libxml-ruby/blob/REL_1_1_3/ext/libxml/extconf.rb#L5-12

While this is a thing you should probably not write it does exist in the wild.
----------------------------------------
Feature #6609: Toplevel as self extended module
https://bugs.ruby-lang.org/issues/6609#change-27308

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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