Merge pull request #11384 from edx/douglashall/PHX-246/gating_multi_problem_prereq

PHX-246 Multiple problems in a prerequisite sequence causes grading to fail

lms/djangoapps/courseware/grades.py

@@ -842,7 +842,9 @@ def _calculate_score_for_modules(user_id, course, modules):
         if module.category not in ignore_categories and (module.graded or module.has_score):
             module_score = scores_client.get(locations[index])
             if module_score:
-                module_percentages.append(module_score.correct / module_score.total)
+                correct = module_score.correct or 0
+                total = module_score.total or 1
+                module_percentages.append(correct / total)
 
     return sum(module_percentages) / float(len(module_percentages)) if module_percentages else 0
 

lms/djangoapps/courseware/tests/test_grades.py

@@ -19,7 +19,7 @@ from courseware.grades import (
     get_module_score
 )
 from courseware.module_render import get_module
-from courseware.model_data import FieldDataCache
+from courseware.model_data import FieldDataCache, set_score
 from courseware.tests.helpers import (
     LoginEnrollmentTestCase,
     get_request_for_user
@@ -432,6 +432,29 @@ class TestGetModuleScore(LoginEnrollmentTestCase, ModuleStoreTestCase):
             score = get_module_score(self.request.user, self.course, self.seq1)
         self.assertEqual(score, .5)
 
+    def test_get_module_score_with_empty_score(self):
+        """
+        Test test_get_module_score_with_empty_score
+        """
+        set_score(self.request.user.id, self.problem1.location, None, None)  # pylint: disable=no-member
+        set_score(self.request.user.id, self.problem2.location, None, None)  # pylint: disable=no-member
+
+        with self.assertNumQueries(1):
+            score = get_module_score(self.request.user, self.course, self.seq1)
+        self.assertEqual(score, 0)
+
+        answer_problem(self.course, self.request, self.problem1)
+
+        with self.assertNumQueries(1):
+            score = get_module_score(self.request.user, self.course, self.seq1)
+        self.assertEqual(score, 0.5)
+
+        answer_problem(self.course, self.request, self.problem2)
+
+        with self.assertNumQueries(1):
+            score = get_module_score(self.request.user, self.course, self.seq1)
+        self.assertEqual(score, 1.0)
+
     def test_get_module_score_with_randomize(self):
         """
         Test test_get_module_score_with_randomize