Bug #4994: DelegateClass don't find extern global public method in 1.9.2

• Status: Rejected
• Assignee: -
• Target version: 1.9.2
• ruby -v: ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

[sylvain303 (Sylvain Viart)]

How to reproduce:

require 'delegate'
require 'pp'

def test_that?(str)
    str.size > 0
end

class String2 < DelegateClass(String)
    def initialize(*param)
        @s = String.new(*param)
        super(@s)
    end

    def dummy
        test_that?(@s)
    end
end

s2 = String2.new("pipo")

pp s2.dummy

The code above works under 1.9.1 and 1.8 but not under 1.9.2

• ruby1.9.1 -v => ruby 1.9.1p378 (2010-01-10 revision 26273) [x86_64-linux]
• ruby1.8 -v => ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
• ruby -v => ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

error message:

!ruby draft/tdelegate.rb
draft/tdelegate.rb:15:in `dummy': undefined method `test_that?' for "pipo":String2 (NoMethodError)
        from draft/tdelegate.rb:21:in `'

shell returned 1

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

It's a spec change for [ruby-dev:39154].

• Delegator now tries to forward all methods as possible,
• but not for private methods, and
• test_that? is a private method.

Probably, it would need a way to tell how the method is called in method_missing.

[sylvain303 (Sylvain Viart)]

Sorry, but links are in Japanese.
I can read the code, but not why the DelegateClass shouldn't search the toplevel method, any more?

Could you translate or post a link to an English doc?

For the correction you suggest, I've wrote this code:
I don't like this usage as a Delegation. May be I missed something.

Edited: Wrong solution, for this method_missing() see comment after

require 'delegate'
require 'pp'

def test_that?(str)
    str.size > 0
end

class String2 < DelegateClass(String)
    def initialize(*param)
        @s = String.new(*param)
        super(@s)
    end

    def dummy
        test_that?(@s)
        # this method is really missing
        bla()
    end

    def method_missing(m, *args, &block)
        begin
            Object.send(m, *args, &block)
        rescue NameError =>e
            # doesn't work with NoMethodError, it loops
            raise "no method found: '#{m}'"
        end
    end
end

s2 = String2.new("pipo")

# test Delegated method
pp s2.size

# call with method_missing()
pp s2.dummy

output (ruby -v ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux])

:!ruby draft/tdelegate.rb
4
draft/tdelegate.rb:24:in `rescue in method_missing': no method found: 'bla' (RuntimeError)
        from draft/tdelegate.rb:20:in `method_missing'
        from draft/tdelegate.rb:16:in `dummy'
        from draft/tdelegate.rb:32:in `'

[sylvain303 (Sylvain Viart)]

The Issue topic could be rewritten: "DelegateClass don't lookup toplevel method in 1.9.2"

Reading and patching the delegate.rb:http://redmine.ruby-lang.org/projects/ruby-19/repository/entry/lib/delegate.rb I've found that it's related to BasicObject's behavior. DelegateClass somewhat inherit from BasicObject, not Object.

This issue follow the same pattern as #3768.

The documentation should be updated how to fix that (toplevel method resolution).

But may be, I'm still miss something about the new Spec about DelegateClass.

[sylvain303 (Sylvain Viart)]

Fixed DelegateClass with method_missing(), somewhat ugly right?

require 'delegate'

def hello
    :hello
end

class MyInt < DelegateClass(Integer)
    def initialize(value)
        @i = value
        super(@i)
        # I want some toplevel here
        @hello = hello()
    end

    def method_missing(m, *args, &block)
        if __getobj__.respond_to?(m)
            __getobj__.__send__(m, *args, &block)
        else
            Object.send(m, *args, &block)
        end
    end
end

ii = MyInt.new(2)
puts p"should call Integer#to_si: #{ii}"
puts "ii.class=#{ii.class}"

output ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

should call Integer#to_si: 2
ii.class=MyInt