added an alias for new to build to the AR collection proxy, this corrects an issue where the collection proxies were not consistent

activerecord/lib/active_record/associations/collection_proxy.rb

@@ -56,6 +56,8 @@ module ActiveRecord
         Array.wrap(association.options[:extend]).each { |ext| proxy_extend(ext) }
       end
 
+      alias_method :new, :build
+
       def respond_to?(*args)
         super ||
         (load_target && target.respond_to?(*args)) ||
@@ -115,14 +117,6 @@ module ActiveRecord
         @association.reload
         self
       end
-
-      def new(*args, &block)
-        if @association.is_a?(HasManyThroughAssociation)
-          @association.build(*args, &block)
-        else
-          method_missing(:new, *args, &block)
-        end
-      end
     end
   end
 end

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -6,8 +6,6 @@ module ActiveRecord
     class HasManyThroughAssociation < HasManyAssociation #:nodoc:
       include ThroughAssociation
 
-      alias_method :new, :build
-
       # Returns the size of the collection by executing a SELECT COUNT(*) query if the collection hasn't been
       # loaded and calling collection.size if it has. If it's more likely than not that the collection does
       # have a size larger than zero, and you need to fetch that collection afterwards, it'll take one fewer

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -245,6 +245,21 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
 
+  def test_new_aliased_to_build
+    devel = Developer.find(1)
+    proj = assert_no_queries { devel.projects.new("name" => "Projekt") }
+    assert !devel.projects.loaded?
+
+    assert_equal devel.projects.last, proj
+    assert devel.projects.loaded?
+
+    assert !proj.persisted?
+    devel.save
+    assert proj.persisted?
+    assert_equal devel.projects.last, proj
+    assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
+  end
+
   def test_build_by_new_record
     devel = Developer.new(:name => "Marcel", :salary => 75000)
     devel.projects.build(:name => "Make bed")

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -537,6 +537,16 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal 3, companies(:first_firm).clients_of_firm(true).size
   end
 
+  def test_new_aliased_to_build
+    company = companies(:first_firm)
+    new_client = assert_no_queries { company.clients_of_firm.new("name" => "Another Client") }
+    assert !company.clients_of_firm.loaded?
+
+    assert_equal "Another Client", new_client.name
+    assert !new_client.persisted?
+    assert_equal new_client, company.clients_of_firm.last
+  end
+
   def test_build
     company = companies(:first_firm)
     new_client = assert_no_queries { company.clients_of_firm.build("name" => "Another Client") }