Refactor DownloadBehavior

Extract derivative_download_options so that it's easier to override

app/controllers/concerns/curation_concerns/download_behavior.rb

@@ -21,14 +21,20 @@ def show
         # For derivatives stored on the local file system
         response.headers['Accept-Ranges'] = 'bytes'
         response.headers['Content-Length'] = File.size(file).to_s
-        send_file file, type: mime_type_for(file), disposition: 'inline'
+        send_file file, derivative_download_options
       else
         render_404
       end
     end
 
     protected
 
+      # Override this method if you want to change the options sent when downloading
+      # a derivative file
+      def derivative_download_options
+        { type: mime_type_for(file), disposition: 'inline' }
+      end
+
       # Customize the :download ability in your Ability class, or override this method
       def authorize_download!
         # authorize! :download, file # can't use this because Hydra::Ability#download_permissions assumes that files are in Basic Container (and thus include the asset's uri)

spec/controllers/downloads_controller_spec.rb

@@ -73,4 +73,12 @@
       end
     end
   end
+
+  describe "derivative_download_options" do
+    before do
+      allow(controller).to receive(:default_file).and_return 'world.png'
+    end
+    subject { controller.send(:derivative_download_options) }
+    it { is_expected.to eq(disposition: 'inline', type: 'image/png') }
+  end
 end