Fix word cloud modules not exporting correctly.

cms/djangoapps/contentstore/tests/test_contentstore.py

@@ -855,6 +855,34 @@ class ContentStoreToyCourseTest(ModuleStoreTestCase):
 
         shutil.rmtree(root_dir)
 
+    def test_export_course_with_metadata_only_word_cloud(self):
+        """
+        Similar to `test_export_course_with_metadata_only_video`.
+        """
+        module_store = modulestore('direct')
+        draft_store = modulestore('draft')
+        content_store = contentstore()
+
+        import_from_xml(module_store, 'common/test/data/', ['word_cloud'])
+        location = CourseDescriptor.id_to_location('HarvardX/ER22x/2013_Spring')
+
+        verticals = module_store.get_items(['i4x', 'HarvardX', 'ER22x', 'vertical', None, None])
+
+        self.assertGreater(len(verticals), 0)
+
+        parent = verticals[0]
+
+        ItemFactory.create(parent_location=parent.location, category="word_cloud", display_name="untitled")
+
+        root_dir = path(mkdtemp_clean())
+
+        print 'Exporting to tempdir = {0}'.format(root_dir)
+
+        # export out to a tempdir
+        export_to_xml(module_store, content_store, location, root_dir, 'test_export', draft_modulestore=draft_store)
+
+        shutil.rmtree(root_dir)
+
     def test_course_handouts_rewrites(self):
         module_store = modulestore('direct')
 

common/lib/xmodule/xmodule/word_cloud_module.py

@@ -9,6 +9,8 @@ If student have answered - words he entered and cloud.
 import json
 import logging
 
+from lxml import etree
+
 from pkg_resources import resource_string
 from xmodule.raw_module import RawDescriptor
 from xmodule.editing_module import MetadataOnlyEditingDescriptor
@@ -244,3 +246,9 @@ class WordCloudDescriptor(WordCloudFields, MetadataOnlyEditingDescriptor, RawDes
     """Descriptor for WordCloud Xmodule."""
     module_class = WordCloudModule
     template_dir_name = 'word_cloud'
+
+    def definition_to_xml(self, resource_fs):
+        """
+        Since there's no real data, just return an empty XML tag.
+        """
+        return etree.fromstring('<word_cloud />')