Re-define empty? for errors to check if the values inside the OrderedHash are...

Re-define empty? for errors to check if the values inside the OrderedHash are empty rather than the OrderedHash itself. [#4356 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

activemodel/lib/active_model/errors.rb

@@ -142,6 +142,11 @@ def count
       to_a.size
     end
 
+    # Returns true if there are any errors, false if not.
+    def empty?
+      all? { |k, v| v && v.empty? }
+    end
+
     # Returns an xml formatted representation of the Errors hash.
     # 
     #   p.errors.add(:name, "can't be blank")

activemodel/test/cases/validations_test.rb

@@ -97,6 +97,12 @@ def test_errors_on_base
     assert_equal 2, r.errors.count
   end
 
+  def test_errors_empty_after_errors_on_check
+    t = Topic.new
+    assert t.errors[:id].empty?
+    assert t.errors.empty?
+  end
+
   def test_validates_each
     hits = 0
     Topic.validates_each(:title, :content, [:title, :content]) do |record, attr|