render_to_string must ensure that response_body

is nil

[ #5875 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

actionpack/lib/abstract_controller/rendering.rb

@@ -113,7 +113,7 @@ module AbstractController
     def render_to_string(*args, &block)
       options = _normalize_args(*args, &block)
       _normalize_options(options)
-      render_to_body(options)
+      render_to_body(options).tap { self.response_body = nil }
     end
 
     # Raw rendering of a template to a Rack-compatible body.

actionpack/test/controller/render_json_test.rb

@@ -26,6 +26,10 @@ class RenderJsonTest < ActionController::TestCase
       render :json => nil
     end
 
+    def render_json_render_to_string
+      render :text => render_to_string(:json => '[]')
+    end
+
     def render_json_hello_world
       render :json => ActiveSupport::JSON.encode(:hello => 'world')
     end
@@ -76,6 +80,12 @@ class RenderJsonTest < ActionController::TestCase
     assert_equal 'application/json', @response.content_type
   end
 
+  def test_render_json_render_to_string
+    get :render_json_render_to_string
+    assert_equal '[]', @response.body
+  end
+
+
   def test_render_json
     get :render_json_hello_world
     assert_equal '{"hello":"world"}', @response.body