From: "dbussink (Dirkjan Bussink)" Date: 2012-11-24T18:10:41+09:00 Subject: [ruby-core:50029] [ruby-trunk - Feature #4085] Refinements and nested methods Issue #4085 has been updated by dbussink (Dirkjan Bussink). Here are few points I'd like to make as to why I think the feature should not be part of 2.0. First of all, there is currently not a single idea / design that describes what refinements are. In this issue different approaches and ideas are explored. This is of course a good thing, but it also means that we haven't come to a conclusion. This means that if refinements were to be part of Ruby 2.0, they would be an implementation that hasn't been fleshed out, is still being debated and can change in the future. I think doing this would be a great disservice to the Ruby community. This is because we would release a feature that people cannot depend on. It may change in the future, break people's code and cause heavy debates on whether we can actually change it in the future. As a reference, originally in 1.9, Hash being insertion ordered was defined as an implementation detail of CRuby. The position of CRuby in the community however, means that this also turned into spec since people depend on it. This was basically a decision made for us by the community, neither JRuby or Rubinius could say, for us it's not insertion ordered. This means that if some things are released, what is and what is not defined behavior is not always just up to the implementers. The Ruby community will come to expect certain behavior of certain features and depend on it. If Ruby 2.0 is released without a properly defined way of how refinements work and that they will be supported in that way well into the future, we very well may end up with an implementation that no one really likes but has to be supported indefinitely. Ruby is not an experimental language anymore, so asking of the community to accept that this all can change in the future is not the right thing to do. What is part of Ruby the language is something that we should be able to stand behind and say of "we will support this and provide a stable platform for you for the future". If that can't be said of a feature, it should not be added to a released Ruby version. Even if removing the feature for now is a hard decision, I feel it is the correct. We should not fall into a sunk cost fallacy, where the amount of development on it results in feeling like it could not be removed. Please realize that nowhere in the argument I've discussed my personal preferences on the feature itself. The thing is that I don't think that should be even necessary at this point, because of all the unclarity about the feature and how it should work. All in all, I think the Ruby community would be done a great disservice by adding a feature that is still being debated so short before a 2.0 release, does not have clear semantics (looking at the alternatives discussed here) and therefore isn't mature enough to be put out there in the wild. ---------------------------------------- Feature #4085: Refinements and nested methods https://bugs.ruby-lang.org/issues/4085#change-33803 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 -- http://bugs.ruby-lang.org/