PLAT-520 Fix Asset store import of null values

cms/djangoapps/contentstore/views/tests/test_videos.py

@@ -289,12 +289,12 @@ class VideosHandlerTestCase(VideoUploadTestMixin, CourseTestCase):
                 headers={"Content-Type": file_info["content_type"]}
             )
 
-            # Ensure asset store was updated
-            self.assertIsNotNone(
-                modulestore().find_asset_metadata(
-                    self.course.id.make_asset_key(VIDEO_ASSET_TYPE, video_id)
-                )
+            # Ensure asset store was updated and the created_by field was set
+            asset_metadata = modulestore().find_asset_metadata(
+                self.course.id.make_asset_key(VIDEO_ASSET_TYPE, video_id)
             )
+            self.assertIsNotNone(asset_metadata)
+            self.assertEquals(asset_metadata.created_by, self.user.id)
 
             # Ensure VAL was updated
             val_info = get_video_info(video_id)

cms/djangoapps/contentstore/views/videos.py

@@ -334,8 +334,9 @@ def videos_post(course, request):
         )
 
         # persist edx_video_id as uploaded through this course
-        video_meta_data = AssetMetadata(course.id.make_asset_key(VIDEO_ASSET_TYPE, edx_video_id))
-        modulestore().save_asset_metadata(video_meta_data, request.user.id)
+        user_id = request.user.id
+        video_meta_data = AssetMetadata(course.id.make_asset_key(VIDEO_ASSET_TYPE, edx_video_id), created_by=user_id)
+        modulestore().save_asset_metadata(video_meta_data, user_id)
 
         # persist edx_video_id in VAL
         create_video({

common/lib/xmodule/xmodule/assetstore/__init__.py

@@ -195,6 +195,9 @@ class AssetMetadata(object):
                 elif tag == 'locked':
                     # Boolean.
                     value = True if value == "true" else False
+                elif value == 'None':
+                    # None.
+                    value = None
                 elif tag in ('created_on', 'edited_on'):
                     # ISO datetime.
                     value = dateutil.parser.parse(value)
@@ -204,9 +207,6 @@ class AssetMetadata(object):
                 elif tag == 'fields':
                     # Dictionary.
                     value = json.loads(value)
-                elif value == 'None':
-                    # None.
-                    value = None
                 setattr(self, tag, value)
 
     @contract(node='AssetElement')

common/lib/xmodule/xmodule/assetstore/tests/test_asset_xml.py

@@ -57,6 +57,18 @@ class TestAssetXml(unittest.TestCase):
             new_value = getattr(new_asset_md, attr)
             self.assertEqual(orig_value, new_value)
 
+    def test_export_with_None_value(self):
+        """
+        Export and import a single AssetMetadata to XML with a None created_by field, without causing an exception.
+        """
+        asset_md = AssetMetadata(
+            self.course_id.make_asset_key('asset', 'none_value'),
+            created_by=None,
+        )
+        asset = etree.Element("asset")
+        asset_md.to_xml(asset)
+        asset_md.from_xml(asset)
+
     def test_export_all_assets_to_xml(self):
         """
         Export all AssetMetadatas to XML and verify the structure and fields.