3 files changed, 9 insertions, 3 deletions
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helper.rb b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
index f6abea38ed..a32beb6100 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
@@ -516,7 +516,8 @@ module ActionView
         def compute_public_path(source, dir, ext = nil, include_host = true)
           has_request = @controller.respond_to?(:request)
 
-          if ext && (File.extname(source).blank? || File.exist?(File.join(ASSETS_DIR, dir, "#{source}.#{ext}")))
+          source_ext = File.extname(source)[1..-1]
+          if ext && (source_ext.blank? || (ext != source_ext && File.exist?(File.join(ASSETS_DIR, dir, "#{source}.#{ext}"))))
             source += ".#{ext}"
           end
 
diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index 2ac2427884..0651f75cfb 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -971,7 +971,8 @@ module ActionView
               @template.fields_for(child_name, child, *args, &block)
             end.join
           else
-            @template.fields_for(name, association, *args, &block)
+            object = args.first.respond_to?(:new_record?) ? args.first : association
+            @template.fields_for(name, object, *args, &block)
           end
         end
 
diff --git a/actionpack/lib/action_view/paths.rb b/actionpack/lib/action_view/paths.rb
index ee26542a07..c7d6fd696a 100644
--- a/actionpack/lib/action_view/paths.rb
+++ b/actionpack/lib/action_view/paths.rb
@@ -2,7 +2,11 @@ module ActionView #:nodoc:
   class PathSet < Array #:nodoc:
     def self.type_cast(obj)
       if obj.is_a?(String)
-        Template::EagerPath.new(obj)
+        if !Object.const_defined?(:Rails) || Rails.configuration.cache_classes
+          Template::EagerPath.new(obj)
+        else
+          Template::Path.new(obj)
+        end
       else
         obj
       end