Fix visibility of some methods when using DelegateClass

Public instance methods added to a delegated class after the
creation of the delegate class were not returned by the
public_instance_methods class method of the delegate class.

Protected instance methods in the delegated class when the
delegate class is created were returned by the public_methods
instance method of the delegate class.

Patch mostly from Kenichi Kamiya <kachick1@gmail.com> in
GitHub pull request 926.  Minor changes to get it to apply,
and to fix tests after applying by me.

Fixes [Bug #11512]

lib/delegate.rb

@@ -393,9 +393,11 @@ end
 #
 def DelegateClass(superclass, &block)
   klass = Class.new(Delegator)
-  methods = superclass.instance_methods
-  methods -= ::Delegator.public_api
-  methods -= [:to_s, :inspect, :=~, :!~, :===]
+  ignores = [*::Delegator.public_api, :to_s, :inspect, :=~, :!~, :===]
+  protected_instance_methods = superclass.protected_instance_methods
+  protected_instance_methods -= ignores
+  public_instance_methods = superclass.public_instance_methods
+  public_instance_methods -= ignores
   klass.module_eval do
     def __getobj__ # :nodoc:
       unless defined?(@delegate_dc_obj)
@@ -408,12 +410,16 @@ def DelegateClass(superclass, &block)
       __raise__ ::ArgumentError, "cannot delegate to self" if self.equal?(obj)
       @delegate_dc_obj = obj
     end
-    methods.each do |method|
+    protected_instance_methods.each do |method|
+      define_method(method, Delegator.delegating_block(method))
+      protected method
+    end
+    public_instance_methods.each do |method|
       define_method(method, Delegator.delegating_block(method))
     end
   end
   klass.define_singleton_method :public_instance_methods do |all=true|
-    super(all) - superclass.protected_instance_methods
+    super(all) | superclass.public_instance_methods
   end
   klass.define_singleton_method :protected_instance_methods do |all=true|
     super(all) | superclass.protected_instance_methods

test/test_delegate.rb

@@ -85,6 +85,37 @@ class TestDelegateClass < Test::Unit::TestCase
     assert_equal(:m, bar.send(:delegate_test_m), bug)
   end
 
+  class Parent
+    def parent_public; end
+
+    protected
+
+    def parent_protected; end
+  end
+
+  class Child < DelegateClass(Parent)
+  end
+
+  class Parent
+    def parent_public_added; end
+
+    protected
+
+    def parent_protected_added; end
+  end
+
+  def test_public_instance_methods
+    ignores = Object.public_instance_methods | Delegator.public_instance_methods
+    assert_equal([:parent_public, :parent_public_added], (Child.public_instance_methods - ignores).sort)
+    assert_equal([:parent_public, :parent_public_added], (Child.new(Parent.new).public_methods - ignores).sort)
+  end
+
+  def test_protected_instance_methods
+    ignores = Object.protected_instance_methods | Delegator.protected_instance_methods
+    assert_equal([:parent_protected, :parent_protected_added], (Child.protected_instance_methods - ignores).sort)
+    assert_equal([:parent_protected, :parent_protected_added], (Child.new(Parent.new).protected_methods - ignores).sort)
+  end
+
   class IV < DelegateClass(Integer)
     attr_accessor :var