Fail informatively in #respond_with when no appropriate #api_behavior renderer is available.

Currently if a user calls #respond_with(csvable), but has not csv
renderer available, Responder will just run through the default render
behavior twice, raising ActionView::MissingTemplate both times.

This changes ActionController::Metal::Responder#api_behavior to check
in advance whether there is a renderer available, and raise
ActionController::MissingRenderer if not.

1 files changed, 31 insertions, 0 deletions

diff --git a/actionpack/test/controller/mime/respond_with_test.rb b/actionpack/test/controller/mime/respond_with_test.rb
index 582050b78c..29ddbff8d4 100644
--- a/actionpack/test/controller/mime/respond_with_test.rb
+++ b/actionpack/test/controller/mime/respond_with_test.rb
@@ -107,6 +107,20 @@ class RenderJsonRespondWithController < RespondWithController
   end
 end
 
+class CsvRespondWithController < ActionController::Base
+  respond_to :csv
+
+  class RespondWithCsv
+    def to_csv
+      "c,s,v"
+    end
+  end
+
+  def index
+    respond_with(RespondWithCsv.new)
+  end
+end
+
 class EmptyRespondWithController < ActionController::Base
   def index
     respond_with(Customer.new("david", 13))
@@ -607,6 +621,23 @@ class RespondWithControllerTest < ActionController::TestCase
     RespondWithController.responder = ActionController::Responder
   end
 
+  def test_uses_renderer_if_an_api_behavior
+    ActionController::Renderers.add :csv do |obj, options|
+      send_data obj.to_csv, type: Mime::CSV
+    end
+    @controller = CsvRespondWithController.new
+    get :index, format: 'csv'
+    assert_equal Mime::CSV, @response.content_type
+    assert_equal "c,s,v", @response.body
+  end
+
+  def test_raises_missing_renderer_if_an_api_behavior_with_no_renderer
+    @controller = CsvRespondWithController.new
+    assert_raise ActionController::MissingRenderer do
+      get :index, format: 'csv'
+    end
+  end
+
   def test_error_is_raised_if_no_respond_to_is_declared_and_respond_with_is_called
     @controller = EmptyRespondWithController.new
     @request.accept = "*/*"