2.3.partial_updates.patch

diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 65434fb..829299a 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -224,9 +224,9 @@ module ActiveRecord
       #   # creates avatar_attributes= and posts_attributes=
       #   accepts_nested_attributes_for :avatar, :posts, :allow_destroy => true
       def accepts_nested_attributes_for(*attr_names)
-        options = { :allow_destroy => false, :update_only => false }
+        options = { :allow_destroy => false, :update_only => false, :partial_updates => false }
         options.update(attr_names.extract_options!)
-        options.assert_valid_keys(:allow_destroy, :reject_if, :limit, :update_only)
+        options.assert_valid_keys(:allow_destroy, :reject_if, :limit, :update_only, :partial_updates)
         options[:reject_if] = REJECT_ALL_BLANK_PROC if options[:reject_if] == :all_blank
 
         attr_names.each do |association_name|
@@ -342,12 +342,16 @@ module ActiveRecord
 
       association = send(association_name)
 
-      existing_records = if association.loaded?
-        association.to_a
-      else
-        attribute_ids = attributes_collection.map {|a| a['id'] || a[:id] }.compact
-        attribute_ids.present? ? association.all(:conditions => {association.primary_key => attribute_ids}) : []
-      end
+      existing_records = if options[:partial_updates]
+                           if association.loaded?
+                             association.to_a
+                           else
+                             attribute_ids = attributes_collection.map {|a| a['id'] || a[:id] }.compact
+                             attribute_ids.present? ? association.all(:conditions => {association.primary_key => attribute_ids}) : []
+                           end
+                         else
+                           association
+                         end
 
       attributes_collection.each do |attributes|
         attributes = attributes.with_indifferent_access
@@ -357,7 +361,7 @@ module ActiveRecord
             association.build(attributes.except(*UNASSIGNABLE_KEYS))
           end
         elsif existing_record = existing_records.detect { |record| record.id.to_s == attributes['id'].to_s }
-          association.send(:add_record_to_target_with_callbacks, existing_record) unless association.loaded?
+          association.send(:add_record_to_target_with_callbacks, existing_record) if !association.loaded? && options[:partial_updates]
           assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
         else
           raise_nested_attributes_record_not_found(association_name, attributes['id'])
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index 3adcc88..b73f231 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -456,13 +456,16 @@ module NestedAttributesOnACollectionAssociationTests
   end
 
   def test_should_not_load_association_when_updating_existing_records
-    @pirate.reload
-    @pirate.send(association_setter, [{ :id => @child_1.id, :name => 'Grace OMalley' }])
-    assert ! @pirate.send(@association_name).loaded?
+    Man.accepts_nested_attributes_for(:interests, :partial_updates => true)
+    Man.create(:name => 'John',
+               :interests_attributes => [{:topic=>'Cars'}])
+    m = Man.last
+    m.interests_attributes = [{:id => m.interests.last.id, :topic=>'Trucks'}]
+    assert ! m.interests.loaded?
 
-    @pirate.save
-    assert ! @pirate.send(@association_name).loaded?
-    assert_equal 'Grace OMalley', @child_1.reload.name
+    m.save
+    assert ! m.interests.loaded?
+    assert_equal 'Trucks', m.interests.last.reload.topic
   end
 
   def test_should_not_overwrite_unsaved_updates_when_loading_association
@@ -652,6 +655,17 @@ module NestedAttributesOnACollectionAssociationTests
     Interest.reflect_on_association(:man).options[:inverse_of] = :interests
   end
 
+  def test_validate_presence_of_parent_fails_if_son_fails_without_reloading
+    Man.accepts_nested_attributes_for(:interests)
+    Interest.validates_presence_of(:topic)
+    Man.create(:name => 'John',
+               :interests_attributes => [{:topic=>'Cars'}])
+    m = Man.last
+    m.interests_attributes = [{:id => m.interests.last.id, :topic=>''}]
+    assert !m.interests.last.valid?
+    assert !m.valid?
+  end
+
   private
 
   def association_setter