Forum: Ruby-core [ruby-trunk - Feature #5582][Open] Allow clone of singleton methods on a BasicObject

Issue #5582 has been reported by Simon Chiang.

----------------------------------------
Feature #5582: Allow clone of singleton methods on a BasicObject
http://redmine.ruby-lang.org/issues/5582

Author: Simon Chiang
Status: Open
Priority: Normal
Assignee:
Category:
Target version: 1.9.2


Currently I do not know of a way to implement something like 'clone' on 
a BasicObject subclass.  This is as close as I've gotten but as you can 
see the singleton methods are not propagated to the clone.

    require 'test/unit'

    class Context < BasicObject
      def _singleton_class_
        class << self
          SINGLETON_CLASS = self
          def _singleton_class_
            SINGLETON_CLASS
          end
        end
        _singleton_class_
      end

      def _class_
        _singleton_class_.superclass
      end

      def _extend_(mod)
        mod.__send__(:extend_object, self)
      end

      def _initialize_clone_(orig)
        # set variables as needed
      end

      def _clone_
        clone = _class_.allocate
        clone._initialize_clone_(self)
        _singleton_class_.included_modules.each {|mod| clone._extend_ 
mod }
        clone
      end
    end

    class ContextTest < Test::Unit::TestCase
      module A
        def a
          :a
        end
      end

      def test__clone__inherits_modules
        context = Context.new
        context._extend_ A
        clone = context._clone_
        assert_equal :a, clone.a
      end

      def test__clone__inherits_singleton_methods
        context = Context.new

        def context.a
          :a
        end

        clone = context._clone_
        assert_equal :a, clone.a  # fails
      end
    end

Is there a way to do this that I don't see? If not, then I request that 
a way be added - perhaps by allowing the singleton_class to be set 
somehow.

In my case I am using Context as the context for a dsl where methods 
write to a target (an instance variable).  I want to be able to clone a 
context such that I can have multiple contexts with the same methods, 
including extensions and singletons, that write to different targets.

Thank you.

Issue #5582 has been updated by George Koehler.


=begin
My first attempt:

 module Clone
   include Kernel
   (instance_methods - [:clone, :initialize_clone]).each {|m| 
undef_method m}
 end

 b = BasicObject.new
 class << b
   include ::Clone
   def single; "Quack!"; end
 end

 c = b.clone
 puts c.single

Output:

 scratch.rb:3: warning: undefining `object_id' may cause serious 
problems
 Quack!

Clone inherits from Kernel, but undefines all its instance methods 
except Clone#clone and Clone#initialize_clone. This technique has some 
awful side effects: Kernel === b and Kernel === c become true. Clone 
might inherit metamethods from Kernel (because I only undefined instance 
methods, not metamethods).
=end

----------------------------------------
Feature #5582: Allow clone of singleton methods on a BasicObject
http://redmine.ruby-lang.org/issues/5582

Author: Simon Chiang
Status: Open
Priority: Normal
Assignee:
Category:
Target version: 1.9.2


Currently I do not know of a way to implement something like 'clone' on 
a BasicObject subclass.  This is as close as I've gotten but as you can 
see the singleton methods are not propagated to the clone.

    require 'test/unit'

    class Context < BasicObject
      def _singleton_class_
        class << self
          SINGLETON_CLASS = self
          def _singleton_class_
            SINGLETON_CLASS
          end
        end
        _singleton_class_
      end

      def _class_
        _singleton_class_.superclass
      end

      def _extend_(mod)
        mod.__send__(:extend_object, self)
      end

      def _initialize_clone_(orig)
        # set variables as needed
      end

      def _clone_
        clone = _class_.allocate
        clone._initialize_clone_(self)
        _singleton_class_.included_modules.each {|mod| clone._extend_ 
mod }
        clone
      end
    end

    class ContextTest < Test::Unit::TestCase
      module A
        def a
          :a
        end
      end

      def test__clone__inherits_modules
        context = Context.new
        context._extend_ A
        clone = context._clone_
        assert_equal :a, clone.a
      end

      def test__clone__inherits_singleton_methods
        context = Context.new

        def context.a
          :a
        end

        clone = context._clone_
        assert_equal :a, clone.a  # fails
      end
    end

Is there a way to do this that I don't see? If not, then I request that 
a way be added - perhaps by allowing the singleton_class to be set 
somehow.

In my case I am using Context as the context for a dsl where methods 
write to a target (an instance variable).  I want to be able to clone a 
context such that I can have multiple contexts with the same methods, 
including extensions and singletons, that write to different targets.

Thank you.

Issue #5582 has been updated by mame (Yusuke Endoh).

Status changed from Open to Assigned
Assignee set to matz (Yukihiro Matsumoto)


----------------------------------------
Feature #5582: Allow clone of singleton methods on a BasicObject
https://bugs.ruby-lang.org/issues/5582#change-25250

Author: thinkerbot (Simon Chiang)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category:
Target version: 1.9.2


Currently I do not know of a way to implement something like 'clone' on 
a BasicObject subclass.  This is as close as I've gotten but as you can 
see the singleton methods are not propagated to the clone.

    require 'test/unit'

    class Context < BasicObject
      def _singleton_class_
        class << self
          SINGLETON_CLASS = self
          def _singleton_class_
            SINGLETON_CLASS
          end
        end
        _singleton_class_
      end

      def _class_
        _singleton_class_.superclass
      end

      def _extend_(mod)
        mod.__send__(:extend_object, self)
      end

      def _initialize_clone_(orig)
        # set variables as needed
      end

      def _clone_
        clone = _class_.allocate
        clone._initialize_clone_(self)
        _singleton_class_.included_modules.each {|mod| clone._extend_ 
mod }
        clone
      end
    end

    class ContextTest < Test::Unit::TestCase
      module A
        def a
          :a
        end
      end

      def test__clone__inherits_modules
        context = Context.new
        context._extend_ A
        clone = context._clone_
        assert_equal :a, clone.a
      end

      def test__clone__inherits_singleton_methods
        context = Context.new

        def context.a
          :a
        end

        clone = context._clone_
        assert_equal :a, clone.a  # fails
      end
    end

Is there a way to do this that I don't see? If not, then I request that 
a way be added - perhaps by allowing the singleton_class to be set 
somehow.

In my case I am using Context as the context for a dsl where methods 
write to a target (an instance variable).  I want to be able to clone a 
context such that I can have multiple contexts with the same methods, 
including extensions and singletons, that write to different targets.

Thank you.

Issue #5582 has been updated by mame (Yusuke Endoh).

Target version changed from 1.9.2 to next minor


----------------------------------------
Feature #5582: Allow clone of singleton methods on a BasicObject
https://bugs.ruby-lang.org/issues/5582#change-33788

Author: thinkerbot (Simon Chiang)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category:
Target version: next minor


Currently I do not know of a way to implement something like 'clone' on 
a BasicObject subclass.  This is as close as I've gotten but as you can 
see the singleton methods are not propagated to the clone.

    require 'test/unit'

    class Context < BasicObject
      def _singleton_class_
        class << self
          SINGLETON_CLASS = self
          def _singleton_class_
            SINGLETON_CLASS
          end
        end
        _singleton_class_
      end

      def _class_
        _singleton_class_.superclass
      end

      def _extend_(mod)
        mod.__send__(:extend_object, self)
      end

      def _initialize_clone_(orig)
        # set variables as needed
      end

      def _clone_
        clone = _class_.allocate
        clone._initialize_clone_(self)
        _singleton_class_.included_modules.each {|mod| clone._extend_ 
mod }
        clone
      end
    end

    class ContextTest < Test::Unit::TestCase
      module A
        def a
          :a
        end
      end

      def test__clone__inherits_modules
        context = Context.new
        context._extend_ A
        clone = context._clone_
        assert_equal :a, clone.a
      end

      def test__clone__inherits_singleton_methods
        context = Context.new

        def context.a
          :a
        end

        clone = context._clone_
        assert_equal :a, clone.a  # fails
      end
    end

Is there a way to do this that I don't see? If not, then I request that 
a way be added - perhaps by allowing the singleton_class to be set 
somehow.

In my case I am using Context as the context for a dsl where methods 
write to a target (an instance variable).  I want to be able to clone a 
context such that I can have multiple contexts with the same methods, 
including extensions and singletons, that write to different targets.

Thank you.

Issue #5582 has been updated by nobu (Nobuyoshi Nakada).


=begin
2.0 allows `method transplanting'.

  module Clone
    %i[clone initialize_copy initialize_dup initialize_clone].each do 
|m|
      define_method(m, Kernel.instance_method(m))
    end
  end
=end

----------------------------------------
Feature #5582: Allow clone of singleton methods on a BasicObject
https://bugs.ruby-lang.org/issues/5582#change-34663

Author: thinkerbot (Simon Chiang)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category:
Target version: next minor


Currently I do not know of a way to implement something like 'clone' on 
a BasicObject subclass.  This is as close as I've gotten but as you can 
see the singleton methods are not propagated to the clone.

    require 'test/unit'

    class Context < BasicObject
      def _singleton_class_
        class << self
          SINGLETON_CLASS = self
          def _singleton_class_
            SINGLETON_CLASS
          end
        end
        _singleton_class_
      end

      def _class_
        _singleton_class_.superclass
      end

      def _extend_(mod)
        mod.__send__(:extend_object, self)
      end

      def _initialize_clone_(orig)
        # set variables as needed
      end

      def _clone_
        clone = _class_.allocate
        clone._initialize_clone_(self)
        _singleton_class_.included_modules.each {|mod| clone._extend_ 
mod }
        clone
      end
    end

    class ContextTest < Test::Unit::TestCase
      module A
        def a
          :a
        end
      end

      def test__clone__inherits_modules
        context = Context.new
        context._extend_ A
        clone = context._clone_
        assert_equal :a, clone.a
      end

      def test__clone__inherits_singleton_methods
        context = Context.new

        def context.a
          :a
        end

        clone = context._clone_
        assert_equal :a, clone.a  # fails
      end
    end

Is there a way to do this that I don't see? If not, then I request that 
a way be added - perhaps by allowing the singleton_class to be set 
somehow.

In my case I am using Context as the context for a dsl where methods 
write to a target (an instance variable).  I want to be able to clone a 
context such that I can have multiple contexts with the same methods, 
including extensions and singletons, that write to different targets.

Thank you.