delegate.rb: ignore unset target

* lib/delegate.rb (Delegator#method_missing): ignore the target if not
  set, and delegate to global methods.  [ruby-core:58572] [Bug #9155]
* lib/delegate.rb (Delegator#respond_to_missing): ditto.
* lib/delegate.rb (SimpleDelegator#__getobj__): yield and return if
  not delegated but a block is given, like as Hash#fetch.
* lib/delegate.rb (DelegateClass#__getobj__): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43984 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 15 insertions, 6 deletions

diff --git a/lib/delegate.rb b/lib/delegate.rb
index 0eaf37122b..c33f7e40df 100644
--- a/lib/delegate.rb
+++ b/lib/delegate.rb
@@ -74,9 +74,10 @@ class Delegator < BasicObject
   # Handles the magic of delegation through \_\_getobj\_\_.
   #
   def method_missing(m, *args, &block)
-    target = self.__getobj__
+    r = true
+    target = self.__getobj__ {r = false}
     begin
-      if target.respond_to?(m)
+      if r && target.respond_to?(m)
         target.__send__(m, *args, &block)
       elsif ::Kernel.respond_to?(m, true)
         ::Kernel.instance_method(m).bind(self).(*args, &block)
@@ -93,8 +94,10 @@ class Delegator < BasicObject
   # call through \_\_getobj\_\_.
   #
   def respond_to_missing?(m, include_private)
-    r = self.__getobj__.respond_to?(m, include_private)
-    if r && include_private && !self.__getobj__.respond_to?(m, false)
+    r = true
+    target = self.__getobj__ {r = false}
+    r &&= target.respond_to?(m, include_private)
+    if r && include_private && !target.respond_to?(m, false)
       warn "#{caller(3)[0]}: delegator does not forward private method \##{m}"
       return false
     end
@@ -306,7 +309,10 @@ end
 class SimpleDelegator<Delegator
   # Returns the current object method calls are being delegated to.
   def __getobj__
-    __raise__ ::ArgumentError, "not delegated" unless defined?(@delegate_sd_obj)
+    unless defined?(@delegate_sd_obj)
+      return yield if block_given?
+      __raise__ ::ArgumentError, "not delegated"
+    end
     @delegate_sd_obj
   end
 
@@ -381,7 +387,10 @@ def DelegateClass(superclass)
   methods -= [:to_s,:inspect,:=~,:!~,:===]
   klass.module_eval do
     def __getobj__  # :nodoc:
-      __raise__ ::ArgumentError, "not delegated" unless defined?(@delegate_dc_obj)
+      unless defined?(@delegate_dc_obj)
+        return yield if block_given?
+        __raise__ ::ArgumentError, "not delegated"
+      end
       @delegate_dc_obj
     end
     def __setobj__(obj)  # :nodoc: