Be sure to convert namespaced names to we have 'Parrots name' instead of 'Parrots.name' in error messages.

activemodel/lib/active_model/errors.rb

@@ -97,13 +97,14 @@ module ActiveModel
       full_messages = []
 
       each do |attribute, messages|
-        messages = Array.wrap(messages)
+        messages = Array(messages)
         next if messages.empty?
 
         if attribute == :base
           messages.each {|m| full_messages << m }
         else
-          attr_name = @base.class.human_attribute_name(attribute)
+          attr_name = attribute.to_s.gsub('.', '_').humanize
+          attr_name = @base.class.human_attribute_name(attribute, :default => attr_name)
           options = { :default => ' ', :scope => @base.class.i18n_scope }
           prefix = attr_name + I18n.t(:"errors.format.separator", options)
 

activemodel/test/cases/validations/i18n_validation_test.rb

@@ -57,7 +57,7 @@ class I18nValidationTest < ActiveModel::TestCase
 
   def test_errors_full_messages_translates_human_attribute_name_for_model_attributes
     @person.errors.add('name', 'empty')
-    I18n.expects(:translate).with(:"person.name", :default => ['Name'], :scope => [:activemodel, :attributes], :count => 1).returns('Name')
+    I18n.expects(:translate).with(:"person.name", :default => ['Name', 'Name'], :scope => [:activemodel, :attributes], :count => 1).returns('Name')
     @person.errors.full_messages
   end
 

activemodel/test/cases/validations_test.rb

@@ -71,6 +71,12 @@ class ValidationsTest < ActiveModel::TestCase
     assert_equal 2, r.errors.count
   end
 
+  def test_errors_on_nested_attributes_expands_name
+    t = Topic.new
+    t.errors["replies.name"] << "can't be blank"
+    assert_equal ["Replies name can't be blank"], t.errors.full_messages
+  end
+
   def test_errors_on_base
     r = Reply.new
     r.content = "Mismatch"

activerecord/test/cases/autosave_association_test.rb

@@ -982,6 +982,7 @@ module AutosaveAssociationOnACollectionAssociationTests
 
     assert !@pirate.valid?
     assert_equal ["cannot be blank"], @pirate.errors["#{@association_name}.name"]
+    assert_equal ["#{@association_name.to_s.titleize} name cannot be blank"], @pirate.errors.full_messages
     assert @pirate.errors[@association_name].empty?
   ensure
     I18n.backend.store_translations(:en, :activerecord => { :errors => { :models =>