don't fail zipping empty folders. fixes #5002

Change-Id: I510facebfc85fd617013741d862d3417b66ce341
Reviewed-on: https://gerrit.instructure.com/4949
Reviewed-by: Brian Palmer <brianp@instructure.com>
Tested-by: Hudson <hudson@instructure.com>

lib/content_zipper.rb

@@ -225,7 +225,7 @@ class ContentZipper
   end
   
   def zip_base_folder(zip_attachment, folder)
-    @files_added = false
+    @files_added = true
     @logger.debug("zipping into attachment: #{zip_attachment.id}")
     zip_attachment.workflow_state = 'zipping' #!(:workflow_state => 'zipping')
     zip_attachment.scribd_attempts += 1
@@ -285,9 +285,7 @@ class ContentZipper
       @context = folder.context
       @logger.debug("  found attachment: #{attachment.unencoded_filename}")
       path = folder_names.empty? ? attachment.filename : File.join(folder_names, attachment.unencoded_filename)
-      if add_attachment_to_zip(attachment, zipfile, path)
-        @files_added = true
-      end
+      @files_added = false unless add_attachment_to_zip(attachment, zipfile, path)
     end
     folder.active_sub_folders.select{|f| !@user || f.grants_right?(@user, nil, :read_contents)}.each do |sub_folder|
       new_names = Array.new(folder_names) << sub_folder.name

spec/lib/content_zipper_spec.rb

@@ -47,5 +47,17 @@ describe ContentZipper do
       end
       names.sort.should == ['visible.png', 'visible/sub-vis.png']
     end
+
+    it "should not error on empty folders" do
+      course_with_student(:active_all => true)
+      folder = Folder.root_folders(@course).first
+      attachment = Attachment.new(:display_name => 'my_download.zip')
+      attachment.user_id = @user.id
+      attachment.workflow_state = 'to_be_zipped'
+      attachment.context = folder
+      attachment.save!
+      ContentZipper.process_attachment(attachment, @user)
+      attachment.workflow_state.should == 'zipped'
+    end
   end
 end