in_rendering_context

# File actionview/lib/action_view/base.rb, line 278
    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