adding a test for no method error

activerecord/lib/active_record/associations/association_proxy.rb

@@ -286,19 +286,13 @@ module ActiveRecord
       private
 
         # Forwards any missing method call to the \target.
-        def method_missing(method, *args)
+        def method_missing(method, *args, &block)
           if load_target
-            unless @target.respond_to?(method)
-              message = "undefined method `#{method.to_s}' for \"#{@target}\":#{@target.class.to_s}"
-              raise NoMethodError, message
-            end
-
-            if block_given?
-              @target.send(method, *args)  { |*block_args| yield(*block_args) }
-            else
-              @target.send(method, *args)
-            end
+            return super unless @target.respond_to?(method)
+            @target.send(method, *args, &block)
           end
+        rescue NoMethodError => e
+          raise e, e.message.sub(/ for #<.*$/, " via proxy for #{@target}")
         end
 
         # Should be true if there is a foreign key present on the @owner which

activerecord/test/cases/associations/association_proxy_test.rb

@@ -0,0 +1,52 @@
+require "cases/helper"
+
+module ActiveRecord
+  module Associations
+    class AsssociationProxyTest < ActiveRecord::TestCase
+      class FakeOwner
+        attr_accessor :new_record
+        alias :new_record? :new_record
+
+        def initialize
+          @new_record = false
+        end
+      end
+
+      class FakeReflection < Struct.new(:options, :klass)
+        def initialize options = {}, klass = nil
+          super
+        end
+
+        def check_validity!
+          true
+        end
+      end
+
+      class FakeTarget
+      end
+
+      class FakeTargetProxy < AssociationProxy
+        def association_scope
+          true
+        end
+
+        def find_target
+          FakeTarget.new
+        end
+      end
+
+      def test_method_missing_error
+        reflection = FakeReflection.new({}, Object.new)
+        owner      = FakeOwner.new
+        proxy      = FakeTargetProxy.new(owner, reflection)
+
+        exception = assert_raises(NoMethodError) do
+          proxy.omg
+        end
+
+        assert_match('omg', exception.message)
+        assert_match(FakeTarget.name, exception.message)
+      end
+    end
+  end
+end