Fix a bug in the pretty_error_messages helper.

* Fixes an issue where matchers would fail on models
with an autosaved belongs_to association.

NEWS.md

@@ -1,5 +1,7 @@
 # HEAD
 
+* Fix a bug in validations with autosaved models.
+
 * Fix maximum value detection for the `ensure_inclusion_of` and
 `ensure_exclusion_of` matchers.
 

lib/shoulda/matchers/active_model/helpers.rb

@@ -5,7 +5,10 @@ module Shoulda # :nodoc:
         def pretty_error_messages(obj) # :nodoc:
           obj.errors.map do |attribute, model|
             msg = "#{attribute} #{model}"
-            msg << " (#{obj.send(attribute).inspect})" unless attribute.to_sym == :base
+            if attribute.to_sym != :base && obj.respond_to?(attribute)
+              msg << " (#{obj.send(attribute).inspect})"
+            end
+            msg
           end
         end
 

spec/shoulda/matchers/active_model/validation_message_finder_spec.rb

@@ -70,6 +70,19 @@ describe Shoulda::Matchers::ActiveModel::ValidationMessageFinder do
 
       description.should == 'no errors'
     end
+
+    it 'should not fetch attribute values for errors that were copied from an autosaved belongs_to association' do
+      instance = define_model(:example) do
+        validate do |record|
+          record.errors.add('association.association_attribute', 'is invalid')
+        end
+      end.new
+      finder = Shoulda::Matchers::ActiveModel::ValidationMessageFinder.new(instance, :attribute)
+
+      expected_messages = ['association.association_attribute is invalid']
+      finder.messages_description.should == "errors: #{expected_messages}"
+    end
+
   end
 
   context '#source_description' do