Forum: Ruby-core Refinements and nested methods

Issue #4085 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


What I find inconsistent specifically (and we wouldn't be able to fix it 
later without breaking backward compatibility) is the "super" behavior 
described in your example above (which I'm duplicating below):

class Foo
  def foo; p :Foo; end
  def bar; p :Foo; end
end

class Bar < Foo
  def foo; p :Bar; super; end
end

module R
  refine Foo do
    def foo; p :R; super; end
    def bar; p :R; end
  end
end

using R

b = Bar.new
b.foo # not refined Bar -> Foo
b.bar # refined R (no super)


This is what I'd expect from the code above to find it consistent:

b.foo # p :Bar; p :R; p :Foo - this is what I'd expect something 
different than you, or maybe I misinterpreted you notation above?
b.bar # p :R - I think this is the same you expect reading your example 
above, just wanted to confirm

I can't understand how anything other than the above would be consistent 
from any perspective. Could you please explain the reason behind the 
behavior you want for "super" inside refinements definitions?
----------------------------------------
Feature #4085: Refinements and nested methods
https://bugs.ruby-lang.org/issues/4085#change-34486

Author: shugo (Shugo Maeda)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 2.0.0


=begin
 As I said at RubyConf 2010, I'd like to propose a new features called
 "Refinements."

 Refinements are similar to Classboxes.  However, Refinements doesn't
 support local rebinding as mentioned later.  In this sense,
 Refinements might be more similar to selector namespaces, but I'm not
 sure because I have never seen any implementation of selector
 namespaces.

 In Refinements, a Ruby module is used as a namespace (or classbox) for
 class extensions.  Such class extensions are called refinements.  For
 example, the following module refines Fixnum.

   module MathN
     refine Fixnum do
       def /(other) quo(other) end
     end
   end

 Module#refine(klass) takes one argument, which is a class to be
 extended.  Module#refine also takes a block, where additional or
 overriding methods of klass can be defined.  In this example, MathN
 refines Fixnum so that 1 / 2 returns a rational number (1/2) instead
 of an integer 0.

 This refinement can be enabled by the method using.

   class Foo
     using MathN

     def foo
       p 1 / 2
     end
   end

   f = Foo.new
   f.foo #=> (1/2)
   p 1 / 2

 In this example, the refinement in MathN is enabled in the definition
 of Foo.  The effective scope of the refinement is the innermost class,
 module, or method where using is called; however the refinement is not
 enabled before the call of using.  If there is no such class, module,
 or method, then the effective scope is the file where using is called.
 Note that refinements are pseudo-lexically scoped.  For example,
 foo.baz prints not "FooExt#bar" but "Foo#bar" in the following code:

   class Foo
     def bar
       puts "Foo#bar"
     end

     def baz
       bar
     end
   end

   module FooExt
     refine Foo do
       def bar
         puts "FooExt#bar"
       end
     end
   end

   module Quux
     using FooExt

     foo = Foo.new
     foo.bar  # => FooExt#bar
     foo.baz  # => Foo#bar
   end

 Refinements are also enabled in reopened definitions of classes using
 refinements and definitions of their subclasses, so they are
 *pseudo*-lexically scoped.

   class Foo
     using MathN
   end

   class Foo
     # MathN is enabled in a reopened definition.
     p 1 / 2  #=> (1/2)
   end

   class Bar < Foo
     # MathN is enabled in a subclass definition.
     p 1 / 2  #=> (1/2)
   end

 If a module or class is using refinements, they are enabled in
 module_eval, class_eval, and instance_eval if the receiver is the
 class or module, or an instance of the class.

   module A
     using MathN
   end
   class B
     using MathN
   end
   MathN.module_eval do
     p 1 / 2  #=> (1/2)
   end
   A.module_eval do
     p 1 / 2  #=> (1/2)
   end
   B.class_eval do
     p 1 / 2  #=> (1/2)
   end
   B.new.instance_eval do
     p 1 / 2  #=> (1/2)
   end

 Besides refinements, I'd like to propose new behavior of nested 
methods.
 Currently, the scope of a nested method is not closed in the outer 
method.

   def foo
     def bar
       puts "bar"
     end
     bar
   end
   foo  #=> bar
   bar  #=> bar

 In Ruby, there are no functions, but only methods.  So there are no
 right places where nested methods are defined.  However, if
 refinements are introduced, a refinement enabled only in the outer
 method would be the right place.  For example, the above code is
 almost equivalent to the following code:

   def foo
     klass = self.class
     m = Module.new {
       refine klass do
         def bar
           puts "bar"
         end
       end
     }
     using m
     bar
   end
   foo  #=> bar
   bar  #=> NoMethodError

 The attached patch is based on SVN trunk r29837.
=end

In message "Re: [ruby-core:50641] [ruby-trunk - Feature #4085] 
Refinements and nested methods"
    on Fri, 7 Dec 2012 01:57:55 +0900, "rosenfeld (Rodrigo Rosenfeld 
Rosas)" <rr.rosas@gmail.com> writes:

|This is what I'd expect from the code above to find it consistent:
|
|b.foo # p :Bar; p :R; p :Foo - this is what I'd expect something different than 
you, or maybe I misinterpreted you notation above?
|b.bar # p :R - I think this is the same you expect reading your example above, 
just wanted to confirm

The point is we do not have local rebinding, that means refined method
is only available in lexical scope.  In the example above, super in
Bar#foo is not in the refinement scope.  That's the reason refined
method never called.

This is an artificial example, but in real use-case refinement should
be defined for subclasses as well, when a method is redefined in the
subclasses.  That was original motivation for (abandoned) around
method-like refinement, but I decided it should be covered by
convention.

              matz.