Fix word cloud modules not exporting correctly.

cms/djangoapps/contentstore/tests/test_contentstore.py

@@ -855,6 +855,68 @@ def test_export_course_with_metadata_only_video(self):
 
         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_empty_data_roundtrip(self):
+        """
+        Test that an empty `data` field is preserved through
+        export/import.
+        """
+        module_store = modulestore('direct')
+        draft_store = modulestore('draft')
+        content_store = contentstore()
+
+        import_from_xml(module_store, 'common/test/data/', ['toy'])
+        location = CourseDescriptor.id_to_location('edX/toy/2012_Fall')
+
+        verticals = module_store.get_items(['i4x', 'edX', 'toy', 'vertical', None, None])
+
+        self.assertGreater(len(verticals), 0)
+
+        parent = verticals[0]
+
+        # Create a module, and ensure that its `data` field is empty
+        word_cloud = ItemFactory.create(parent_location=parent.location, category="word_cloud", display_name="untitled")
+        del word_cloud.data
+        self.assertEquals(word_cloud.data, '')
+
+        # Export the course
+        root_dir = path(mkdtemp_clean())
+        export_to_xml(module_store, content_store, location, root_dir, 'test_roundtrip', draft_modulestore=draft_store)
+
+        # Reimport and get the video back
+        import_from_xml(module_store, root_dir)
+        imported_word_cloud = module_store.get_item(Location(['i4x', 'edX', 'toy', 'word_cloud', 'untitled', None]))
+
+        # It should now contain empty data
+        self.assertEquals(imported_word_cloud.data, '')
+
     def test_course_handouts_rewrites(self):
         module_store = modulestore('direct')
 

common/lib/xmodule/xmodule/raw_module.py

@@ -32,3 +32,22 @@ def definition_to_xml(self, resource_fs):
                    context=lines[line - 1][offset - 40:offset + 40],
                    loc=self.location))
             raise Exception, msg, sys.exc_info()[2]
+
+
+class EmptyDataRawDescriptor(XmlDescriptor, XMLEditingDescriptor):
+    """
+    Version of RawDescriptor for modules which may have no XML data,
+    but use XMLEditingDescriptor for import/export handling.
+    """
+    data = String(default='', scope=Scope.content)
+
+    @classmethod
+    def definition_from_xml(cls, xml_object, system):
+        if len(xml_object) == 0 and len(xml_object.items()) == 0:
+            return {'data': ''}, []
+        return {'data': etree.tostring(xml_object, pretty_print=True, encoding='unicode')}, []
+
+    def definition_to_xml(self, resource_fs):
+        if self.data:
+            return etree.fromstring(self.data)
+        return etree.Element(self.category)

common/lib/xmodule/xmodule/video_module.py

@@ -12,7 +12,7 @@
 from django.http import Http404
 
 from xmodule.x_module import XModule
-from xmodule.raw_module import RawDescriptor
+from xmodule.raw_module import EmptyDataRawDescriptor
 from xmodule.editing_module import MetadataOnlyEditingDescriptor
 from xblock.core import Integer, Scope, String, Float, Boolean
 
@@ -97,7 +97,7 @@ def get_html(self):
 
 class VideoDescriptor(VideoFields,
                       MetadataOnlyEditingDescriptor,
-                      RawDescriptor):
+                      EmptyDataRawDescriptor):
     module_class = VideoModule
 
     def __init__(self, *args, **kwargs):
@@ -130,19 +130,15 @@ def from_xml(cls, xml_data, system, org=None, course=None):
         _parse_video_xml(video, video.data)
         return video
 
-    def definition_to_xml(self, resource_fs):
-        """
-        Override the base implementation. We don't actually have anything in the 'data' field
-        (it's an empty string), so we just return a simple XML element
-        """
-        return etree.Element('video')
-
 
 def _parse_video_xml(video, xml_data):
     """
     Parse video fields out of xml_data. The fields are set if they are
     present in the XML.
     """
+    if not xml_data:
+        return
+
     xml = etree.fromstring(xml_data)
 
     display_name = xml.get('display_name')

common/lib/xmodule/xmodule/word_cloud_module.py

@@ -10,7 +10,7 @@
 import logging
 
 from pkg_resources import resource_string
-from xmodule.raw_module import RawDescriptor
+from xmodule.raw_module import EmptyDataRawDescriptor
 from xmodule.editing_module import MetadataOnlyEditingDescriptor
 from xmodule.x_module import XModule
 
@@ -240,7 +240,7 @@ def get_html(self):
         return self.content
 
 
-class WordCloudDescriptor(WordCloudFields, MetadataOnlyEditingDescriptor, RawDescriptor):
+class WordCloudDescriptor(WordCloudFields, MetadataOnlyEditingDescriptor, EmptyDataRawDescriptor):
     """Descriptor for WordCloud Xmodule."""
     module_class = WordCloudModule
     template_dir_name = 'word_cloud'