Add AssociationReflection#collection_association? which returns true …

…if it's for a has_many or has_and_belongs_to_many association.

activerecord/lib/active_record/reflection.rb

@@ -252,10 +252,17 @@ def polymorphic_inverse_of(associated_class)
         end
       end
 
+      # Returns whether or not this association reflection is for a collection
+      # association. Returns +true+ if the +macro+ is one of +has_many+ or
+      # +has_and_belongs_to_many+, +false+ otherwise.
+      def collection_association?
+        [:has_many, :has_and_belongs_to_many].include?(macro)
+      end
+
       private
         def derive_class_name
           class_name = name.to_s.camelize
-          class_name = class_name.singularize if [ :has_many, :has_and_belongs_to_many ].include?(macro)
+          class_name = class_name.singularize if collection_association?
           class_name
         end
 

activerecord/test/cases/reflection_test.rb

@@ -4,6 +4,7 @@
 require 'models/company'
 require 'models/company_in_module'
 require 'models/subscriber'
+require 'models/ship'
 require 'models/pirate'
 require 'models/price_estimate'
 
@@ -194,6 +195,14 @@ def test_has_many_through_reflection
     assert_kind_of ActiveRecord::Reflection::ThroughReflection, Subscriber.reflect_on_association(:books)
   end
 
+  def test_collection_association?
+    assert Pirate.reflect_on_association(:birds).collection_association?
+    assert Pirate.reflect_on_association(:parrots).collection_association?
+
+    assert !Pirate.reflect_on_association(:ship).collection_association?
+    assert !Ship.reflect_on_association(:pirate).collection_association?
+  end
+
   private
     def assert_reflection(klass, association, options)
       assert reflection = klass.reflect_on_association(association)