From 09bb41fbdb8bb7d4cf414d90f43e324908fac801 Mon Sep 17 00:00:00 2001
From: adman65 <me@broadcastingadam.com>
Date: Tue, 3 Jan 2012 13:37:39 +0200
Subject: [PATCH] Add test cases for nil polymorphic associations

---
 lib/active_model/serializer.rb |  4 +++-
 test/serializer_test.rb        | 39 ++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index d59abc58..fbbfe9da 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -131,10 +131,12 @@ module ActiveModel
 
 
         def serialize_ids(object, scope)
-          if polymorphic?
+          if polymorphic? && object
             { 
               polymorphic_key(object) => object.read_attribute_for_serialization(:id),
             }
+          elsif polymorphic? && !object
+            { }
           elsif object
             { key => object.read_attribute_for_serialization(:id) }
           else
diff --git a/test/serializer_test.rb b/test/serializer_test.rb
index d502b226..f8ef7d1a 100644
--- a/test/serializer_test.rb
+++ b/test/serializer_test.rb
@@ -667,6 +667,25 @@ class SerializerTest < ActiveModel::TestCase
     }, serializer.as_json)
   end
 
+  def test_polymorphic_has_one_with_nil
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new
+    blog = polymorphic_blog.new
+    blog.writer = nil
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+    }, serializer.as_json)
+  end
+
   def test_polymorphic_has_one_with_ids
     polymorphic_blog = Class.new do
       attr_accessor :writer
@@ -688,6 +707,26 @@ class SerializerTest < ActiveModel::TestCase
     }, serializer.as_json)
   end
 
+  def test_polymorphic_has_one_id_with_nil
+    polymorphic_blog = Class.new do
+      attr_accessor :writer
+    end
+
+    polymorphic_serializer = Class.new(ActiveModel::Serializer) do
+      embed :ids
+      has_one :writer, :polymorphic => true
+    end
+
+    user = PolymorphicUser.new
+    blog = polymorphic_blog.new
+    blog.writer = nil
+
+    serializer = polymorphic_serializer.new(blog, user)
+
+    assert_equal({
+    }, serializer.as_json)
+  end
+
   def test_root_provided_in_options
     author_serializer = Class.new(ActiveModel::Serializer) do
       attributes :id, :name