Get students experiments, groups, and cohorts

TNL-498

openedx/core/djangoapps/course_groups/cohorts.py

@@ -196,7 +196,7 @@ def get_cohorted_commentables(course_key):
     return ans
 
 
-def get_cohort(user, course_key):
+def get_cohort(user, course_key, assign=True):
     """
     Given a Django user and a CourseKey, return the user's cohort in that
     cohort.
@@ -204,6 +204,7 @@ def get_cohort(user, course_key):
     Arguments:
         user: a Django User object.
         course_key: CourseKey
+        assign (bool): if False then we don't assign a group to user
 
     Returns:
         A CourseUserGroup object if the course is cohorted and the User has a
@@ -230,7 +231,8 @@ def get_cohort(user, course_key):
         )
     except CourseUserGroup.DoesNotExist:
         # Didn't find the group.  We'll go on to create one if needed.
-        pass
+        if not assign:
+            return None
 
     choices = course.auto_cohort_groups
     if len(choices) > 0:

openedx/core/djangoapps/course_groups/tests/test_cohorts.py

@@ -207,6 +207,31 @@ class TestCohorts(TestCase):
             "other_user should be assigned to the default cohort"
         )
 
+    def test_get_cohort_with_assign(self):
+        """
+        Make sure cohorts.get_cohort() returns None if no group is already
+        assigned to a user instead of assigning/creating a group automatically
+        """
+        course = modulestore().get_course(self.toy_course_key)
+        self.assertFalse(course.is_cohorted)
+
+        user = UserFactory(username="test", email="a@b.com")
+
+        # Add an auto_cohort_group to the course...
+        config_course_cohorts(
+            course,
+            discussions=[],
+            cohorted=True,
+            auto_cohort_groups=["AutoGroup"]
+        )
+
+        # get_cohort should return None as no group is assigned to user
+        self.assertIsNone(cohorts.get_cohort(user, course.id, assign=False))
+
+        # get_cohort should return a group for user
+        self.assertEquals(cohorts.get_cohort(user, course.id).name, "AutoGroup")
+
+
     def test_auto_cohorting(self):
         """
         Make sure cohorts.get_cohort() does the right thing with auto_cohort_groups

openedx/core/djangoapps/user_api/partition_schemes.py

@@ -15,15 +15,16 @@ class RandomUserPartitionScheme(object):
     RANDOM = random.Random()
 
     @classmethod
-    def get_group_for_user(cls, course_id, user, user_partition, track_function=None):
+    def get_group_for_user(cls, course_id, user, user_partition, assign=True, track_function=None):
         """
         Returns the group from the specified user position to which the user is assigned.
-        If the user has not yet been assigned, a group will be randomly chosen for them.
+        If the user has not yet been assigned, a group will be randomly chosen for them if assign flag is True.
         """
         partition_key = cls._key_for_partition(user_partition)
         group_id = course_tag_api.get_course_tag(user, course_id, partition_key)
         group = user_partition.get_group(int(group_id)) if not group_id is None else None
-        if group is None:
+
+        if group is None and assign:
             if not user_partition.groups:
                 raise UserPartitionError('Cannot assign user to an empty user partition')
 

openedx/core/djangoapps/user_api/tests/test_partition_schemes.py

@@ -58,6 +58,24 @@ class TestRandomUserPartitionScheme(PartitionTestCase):
             group2_id = RandomUserPartitionScheme.get_group_for_user(self.MOCK_COURSE_ID, self.user, self.user_partition)
             self.assertEqual(group1_id, group2_id)
 
+    def test_get_group_for_user_with_assign(self):
+        """
+        Make sure get_group_for_user returns None if no group is already
+        assigned to a user instead of assigning/creating a group automatically
+        """
+        # We should not get any group because assign is False which will
+        # protect us from automatically creating a group for user
+        group = RandomUserPartitionScheme.get_group_for_user(
+            self.MOCK_COURSE_ID, self.user, self.user_partition, assign=False
+        )
+
+        self.assertIsNone(group)
+
+        # We should get a group automatically assigned to user
+        group = RandomUserPartitionScheme.get_group_for_user(self.MOCK_COURSE_ID, self.user, self.user_partition)
+
+        self.assertIsNotNone(group)
+
     def test_empty_partition(self):
         empty_partition = UserPartition(
             self.TEST_ID,