Merge pull request #3695 from tobiassvn/partial_path_error

Meaningful errors for unexpected partial arguments. Fixes #3573

actionpack/lib/action_view/renderer/partial_renderer.rb

@@ -366,8 +366,13 @@ module ActionView
       path = if object.respond_to?(:to_partial_path)
         object.to_partial_path
       else
-        ActiveSupport::Deprecation.warn "ActiveModel-compatible objects whose classes return a #model_name that responds to #partial_path are deprecated. Please respond to #to_partial_path directly instead."
-        object.class.model_name.partial_path
+        klass = object.class
+        if klass.respond_to?(:model_name)
+          ActiveSupport::Deprecation.warn "ActiveModel-compatible objects whose classes return a #model_name that responds to #partial_path are deprecated. Please respond to #to_partial_path directly instead."
+          klass.model_name.partial_path
+        else
+          raise ArgumentError.new("'#{object.inspect}' is not an ActiveModel-compatible object that returns a valid partial path.")
+        end
       end
 
       @partial_names[path] ||= path.dup.tap do |object_path|

actionpack/test/template/render_test.rb

@@ -142,6 +142,13 @@ module RenderTestCases
                                 "and is followed by any combinations of letters, numbers, or underscores.", e.message
   end
 
+  def test_render_partial_with_incompatible_object
+    @view.render(:partial => nil)
+    flunk "Render did not raise ArgumentError"
+  rescue ArgumentError => e
+    assert_equal "'#{nil.inspect}' is not an ActiveModel-compatible object that returns a valid partial path.", e.message
+  end
+
   def test_render_partial_with_errors
     @view.render(:partial => "test/raise")
     flunk "Render did not raise Template::Error"