From 6875fe118c251d435021b5e77a036816b6cf873b Mon Sep 17 00:00:00 2001
From: David Yip <yipdw@northwestern.edu>
Date: Sun, 8 Mar 2009 05:35:31 -0500
Subject: [PATCH] Render a form with all empty values if a nested association evaluates to nil.

---
 actionpack/lib/action_view/helpers/form_helper.rb |    2 ++
 actionpack/test/template/form_helper_test.rb      |   18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index a589bcb..d4cd4b6 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -1009,6 +1009,8 @@ module ActionView
             children.map do |child|
               fields_for_nested_model("#{name}[#{explicit_child_index || nested_child_index}]", child, args, block)
             end.join
+          elsif association.nil?
+            @template.fields_for(name, *args, &block)
           else
             fields_for_nested_model(name, explicit_object || association, args, block)
           end
diff --git a/actionpack/test/template/form_helper_test.rb b/actionpack/test/template/form_helper_test.rb
index 654eee4..fc14acf 100644
--- a/actionpack/test/template/form_helper_test.rb
+++ b/actionpack/test/template/form_helper_test.rb
@@ -473,6 +473,24 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, output_buffer
   end
 
+  def test_nested_fields_for_with_nil_association
+    @post.author = nil
+
+    form_for('post', @post) do |f|
+      concat f.text_field(:title)
+      f.fields_for :author do |c|
+        concat c.text_field(:name)
+      end
+    end
+
+    expected = '<form action="http://www.example.com" method="post">' +
+               '<input name="post[title]" size="30" type="text" id="post_title" value="Hello World" />' +
+               '<input id="post_author_attributes_name" name="post[author_attributes][name]" size="30" type="text" />' +
+               '</form>'
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_nested_fields_for_with_index_and_parent_fields
     form_for('post', @post, :index => 1) do |c|
       concat c.text_field(:title)
-- 
1.6.1