Common behavior with adding formats to lookup_context for TemplateRenderer and PartialRenderer

4 files changed, 16 insertions, 4 deletions

diff --git a/actionpack/lib/action_view/lookup_context.rb b/actionpack/lib/action_view/lookup_context.rb
index 9f617a9a53..1a656ed37f 100644
--- a/actionpack/lib/action_view/lookup_context.rb
+++ b/actionpack/lib/action_view/lookup_context.rb
@@ -103,7 +103,7 @@ module ActionView
 
     # Helpers related to template lookup using the lookup context information.
     module ViewPaths
-      attr_reader :view_paths
+      attr_reader :view_paths, :html_fallback_for_js
 
       # Whenever setting view paths, makes a copy so we can manipulate then in
       # instance objects as we wish.
@@ -200,7 +200,10 @@ module ActionView
     def formats=(values)
       if values
         values.concat(default_formats) if values.delete "*/*"
-        values << :html if values == [:js]
+        if values == [:js]
+          values << :html
+          @html_fallback_for_js = true
+        end
       end
       super(values)
     end
diff --git a/actionpack/lib/action_view/renderer/abstract_renderer.rb b/actionpack/lib/action_view/renderer/abstract_renderer.rb
index 0b5d3785d4..b79b89e142 100644
--- a/actionpack/lib/action_view/renderer/abstract_renderer.rb
+++ b/actionpack/lib/action_view/renderer/abstract_renderer.rb
@@ -37,5 +37,11 @@ module ActionView
     def instrument(name, options={})
       ActiveSupport::Notifications.instrument("render_#{name}.action_view", options){ yield }
     end
+
+    def prepend_formats(formats)
+      formats = Array(formats)
+      return if formats.empty? || @lookup_context.html_fallback_for_js
+      @lookup_context.formats = formats | @lookup_context.formats
+    end
   end
 end
diff --git a/actionpack/lib/action_view/renderer/partial_renderer.rb b/actionpack/lib/action_view/renderer/partial_renderer.rb
index 71fa05ab3e..f3300e470b 100644
--- a/actionpack/lib/action_view/renderer/partial_renderer.rb
+++ b/actionpack/lib/action_view/renderer/partial_renderer.rb
@@ -281,6 +281,8 @@ module ActionView
       @block   = block
       @details = extract_details(options)
 
+      prepend_formats(options[:formats])
+
       if String === partial
         @object     = options[:object]
         @path       = partial
diff --git a/actionpack/lib/action_view/renderer/template_renderer.rb b/actionpack/lib/action_view/renderer/template_renderer.rb
index a27d5dd1b1..d15e75637a 100644
--- a/actionpack/lib/action_view/renderer/template_renderer.rb
+++ b/actionpack/lib/action_view/renderer/template_renderer.rb
@@ -10,9 +10,10 @@ module ActionView
       template = determine_template(options)
       context  = @lookup_context
 
+      prepend_formats(template.formats)
+
       unless context.rendered_format
-        context.formats = template.formats unless template.formats.empty?
-        context.rendered_format = context.formats.first
+        context.rendered_format = template.formats.first || formats.last
       end
 
       render_template(template, options[:layout], options[:locals])