Add ability to get an individual full error message + test for full_messages.

activemodel/lib/active_model/errors.rb

@@ -180,6 +180,7 @@ def empty?
       all? { |k, v| v && v.empty? }
     end
     alias_method :blank?, :empty?
+
     # Returns an xml formatted representation of the Errors hash.
     #
     #   p.errors.add(:name, "can't be blank")
@@ -254,20 +255,22 @@ def add_on_blank(attributes, options = {})
     #   company.errors.full_messages # =>
     #     ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Email can't be blank"]
     def full_messages
-      map { |attribute, message|
-        if attribute == :base
-          message
-        else
-          attr_name = attribute.to_s.gsub('.', '_').humanize
-          attr_name = @base.class.human_attribute_name(attribute, :default => attr_name)
-
-          I18n.t(:"errors.format", {
-            :default   => "%{attribute} %{message}",
-            :attribute => attr_name,
-            :message   => message
-          })
-        end
-      }
+      map { |attribute, message| full_message(attribute, message) }
+    end
+
+    # Returns a full message for a given attribute.
+    #
+    #   company.errors.full_message(:name, "is invalid")  # =>
+    #     "Name is invalid"
+    def full_message(attribute, message)
+      return message if attribute == :base
+      attr_name = attribute.to_s.gsub('.', '_').humanize
+      attr_name = @base.class.human_attribute_name(attribute, :default => attr_name)
+      I18n.t(:"errors.format", {
+        :default   => "%{attribute} %{message}",
+        :attribute => attr_name,
+        :message   => message
+      })
     end
 
     # Translates an error message in its default scope

activemodel/test/cases/errors_test.rb

@@ -52,7 +52,6 @@ def test_has_key?
     person.validate!
     assert_equal ["name can not be nil"], person.errors.full_messages
     assert_equal ["can not be nil"], person.errors[:name]
-
   end
 
   test 'should be able to assign error' do
@@ -78,7 +77,6 @@ def test_has_key?
     person.errors.add(:name, "can not be blank")
     person.errors.add(:name, "can not be nil")
     assert_equal ["name can not be blank", "name can not be nil"], person.errors.to_a
-
   end
 
   test 'to_hash should return an ordered hash' do
@@ -86,4 +84,22 @@ def test_has_key?
     person.errors.add(:name, "can not be blank")
     assert_instance_of ActiveSupport::OrderedHash, person.errors.to_hash
   end
+
+  test 'full_messages should return an array of error messages, with the attribute name included' do
+    person = Person.new
+    person.errors.add(:name, "can not be blank")
+    person.errors.add(:name, "can not be nil")
+    assert_equal ["name can not be blank", "name can not be nil"], person.errors.to_a
+  end
+
+  test 'full_message should return the given message if attribute equals :base' do
+    person = Person.new
+    assert_equal "press the button", person.errors.full_message(:base, "press the button")
+  end
+
+  test 'full_message should return the given message with the attribute name included' do
+    person = Person.new
+    assert_equal "name can not be blank", person.errors.full_message(:name, "can not be blank")
+  end
+
 end