class ActionView::Base

def in_rendering_context(options)
  old_view_renderer  = @view_renderer
  old_lookup_context = @lookup_context
  if !lookup_context.html_fallback_for_js && options[:formats]
    formats = Array(options[:formats])
    if formats == [:js]
      formats << :html
    end
    @lookup_context = lookup_context.with_prepended_formats(formats)
    @view_renderer = ActionView::Renderer.new @lookup_context
  end
  yield @view_renderer
ensure
  @view_renderer = old_view_renderer
  @lookup_context = old_lookup_context
end