From c7a420d29574c135e4b5d91d81af34bbdc23eade Mon Sep 17 00:00:00 2001
From: Michi Huber <michi.huber@gmail.com>
Date: Tue, 26 Feb 2013 11:17:28 +0100
Subject: [PATCH] Don't fail if object is nil, render null

---
 lib/active_model/serializer.rb |  1 +
 test/serializer_test.rb        | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index b070664c..5cec7187 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -267,6 +267,7 @@ module ActiveModel
     # Returns a hash representation of the serializable
     # object without the root.
     def serializable_hash
+      return nil if @object.nil?
       instrument(:serialize, :serializer => self.class.name) do
         @node = attributes
         instrument :associations do
diff --git a/test/serializer_test.rb b/test/serializer_test.rb
index 9fe10e64..04b3742f 100644
--- a/test/serializer_test.rb
+++ b/test/serializer_test.rb
@@ -254,6 +254,28 @@ class SerializerTest < ActiveModel::TestCase
     assert_equal({ :my_blog => { :author => nil } }, serializer.new(blog, :scope => user).as_json)
   end
 
+  def test_nil_root_object
+    user = User.new
+    blog = nil
+
+    serializer = Class.new(BlogSerializer) do
+      root false
+    end
+
+    assert_equal(nil, serializer.new(blog, :scope => user).as_json)
+  end
+
+  def test_custom_root_with_nil_root_object
+    user = User.new
+    blog = nil
+
+    serializer = Class.new(BlogSerializer) do
+      root :my_blog
+    end
+
+    assert_equal({ :my_blog => nil }, serializer.new(blog, :scope => user).as_json)
+  end
+
   def test_false_root
     user = User.new
     blog = Blog.new