title: render_to_string partial format error in controller
body: <p>I get the below error when running the below code on a controller. Please note the <code>:formats=&gt;[:json]</code> in the error, even though <code>:formats=&gt;[:html]</code> is passed into render_to_string</p>
  
  <p>What am I doing wrong? Any ideas? 
  Actually, the code below worked fine before, not sure what changes influenced this error.
  Rails version: 3.2.8 </p>
  
  <p>btw the template is definitely in place: loc/_search_details.html.erb</p>
  
  <p>Bonus question: where can I find the api documentation showing what parameters can be passed to render_to_string and how it works?</p>
  
  <p>Error:
  <strong>ActionView::MissingTemplate (Missing partial loc/search_details with {:locale=>[:en], :formats=>[:json], :handlers=>[:erb, :builder, :coffee]}.</strong></p>
  
  <pre><code>  respond_to do |format|
      format.json { 
        @detail_str = render_to_string(:partial =&gt; 'loc/search_details', :layout =&gt; false, :formats=&gt;[:html], :locals =&gt; {:beer_results =&gt; @beer_results})
        @list_str = render_to_string(:partial =&gt; 'loc/search_list', :layout =&gt; false,:formats=&gt;[:html], :locals =&gt; {:beer_results =&gt; @beer_results})
        render :json =&gt; {:results =&gt; @results_hash, :result_details =&gt; @detail_str, :result_list =&gt; @list_str }
  
        }
    end
  </code></pre>