Added :format option for form_for helper and spec for this [#5226 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

actionpack/lib/action_view/helpers/form_helper.rb

@@ -202,6 +202,12 @@ module ActionView
       #     ...
       #   <% end %>
       #
+      # You can also set the answer format, like this:
+      #
+      #   <%= form_for(@post, :format => :json) do |f| %>
+      #     ...
+      #   <% end %>
+      #
       # If you have an object that needs to be represented as a different
       # parameter, like a Client that acts as a Person:
       #
@@ -332,7 +338,9 @@ module ActionView
 
         options[:html] ||= {}
         options[:html].reverse_merge!(html_options)
-        options[:url] ||= polymorphic_path(object_or_array)
+        options[:url] ||= options[:format] ? \
+          polymorphic_path(object_or_array, :format => options.delete(:format)) : \
+          polymorphic_path(object_or_array)
       end
 
       # Creates a scope around a specific model object like form_for, but

actionpack/test/template/form_helper_test.rb

@@ -641,6 +641,18 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_for_with_format
+    form_for(@post, :format => :json, :html => { :id => "edit_post_123", :class => "edit_post" }) do |f|
+      concat f.label(:title)
+    end
+
+    expected = whole_form("/posts/123.json", "edit_post_123" , "edit_post", :method => "put") do
+      "<label for='post_title'>Title</label>"
+    end
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_form_for_with_symbol_object_name
     form_for(@post, :as => "other_name", :html => { :id => 'create-post' }) do |f|
       concat f.label(:title, :class => 'post_title')
@@ -1761,8 +1773,12 @@ class FormHelperTest < ActionView::TestCase
       "/posts"
     end
 
-    def post_path(post)
-      "/posts/#{post.id}"
+    def post_path(post, options = {})
+      if options[:format]
+        "/posts/#{post.id}.#{options[:format]}"
+      else
+        "/posts/#{post.id}"
+      end
     end
 
     def protect_against_forgery?