Fix warning for submission in Studio preview

apps/openassessment/xblock/submission_mixin.py

@@ -61,7 +61,9 @@ class SubmissionMixin(object):
 
         # Short-circuit if no user is defined (as in Studio Preview mode)
         # Since students can't submit, they will never be able to progress in the workflow
-        if student_item_dict['student_id'] is None:
+        # Studio Preview provides an anonymous student ID, so we need to check the scope ids directly
+        # to check that we are in preview mode.
+        if self.scope_ids.user_id is None:
             return False, 'ENOPREVIEW', self.submit_errors['ENOPREVIEW']
 
         workflow = self.get_workflow_info()

apps/openassessment/xblock/test/test_submission.py

@@ -3,7 +3,7 @@ Test submission to the OpenAssessment XBlock.
 """
 
 import json
-from mock import patch
+from mock import patch, Mock
 from submissions import api as sub_api
 from submissions.api import SubmissionRequestError, SubmissionInternalError
 from openassessment.xblock.submission_mixin import SubmissionMixin
@@ -50,7 +50,16 @@ class SubmissionTest(XBlockHandlerTestCase):
     # In Studio preview mode, the runtime sets the user ID to None
     @scenario('data/basic_scenario.xml', user_id=None)
     def test_cannot_submit_in_preview_mode(self, xblock,):
+
+        # The Studio runtime apparently provides an anonymous student ID,
+        # even though we're running in Preview mode.  We should check the scope id
+        # to determine whether we're in Preview mode or not.
+        xblock.xmodule_runtime = Mock(
+            course_id='test_course',
+            anonymous_student_id='test_student'
+        )
+
         resp = self.request(xblock, 'submit', self.SUBMISSION, response_format='json')
         self.assertFalse(resp[0])
         self.assertEqual(resp[1], "ENOPREVIEW")
-        self.assertEqual(resp[2], "To submit a response, view this component in Preview or Live mode.")
\ No newline at end of file
+        self.assertEqual(resp[2], "To submit a response, view this component in Preview or Live mode.")