revert-multiple-cohorts: Add checks in code and a management command to ease the revert

common/djangoapps/course_groups/management/commands/revert_workgroup.py

+from django.core.management.base import BaseCommand, CommandError
+from django.core.exceptions import MultipleObjectsReturned
+from optparse import make_option
+
+from django.contrib.auth.models import User
+
+from xmodule.modulestore.django import modulestore
+from xmodule.course_module import CourseDescriptor
+from course_groups.models import CourseUserGroup
+from course_groups.cohorts import (
+    get_cohort,
+    get_cohort_by_name,
+    add_cohort,
+    add_user_to_cohort,
+    remove_user_from_cohort
+)
+from student.models import CourseEnrollment
+
+
+class Command(BaseCommand):
+    option_list = BaseCommand.option_list + (
+        make_option('--fix',
+            action='store_true',
+            dest='fix',
+            default=False,
+            help='Apply possible fixes automatically'),
+    )
+    help = 'Revert the multiple cohorts feature.'
+
+    def handle(self, *args, **options):
+
+        self.stdout.write('### Checking CourseUserGroup group types\n')
+        error = False
+        for course_group in CourseUserGroup.objects.all():
+            if course_group.group_type != CourseUserGroup.COHORT:
+                if options['fix']:
+                    self.stdout.write(
+                        'Fixed: CourseUserGroup with an invalid group_type found: {} (type: {})\n'.format(
+                            course_group.name, course_group.group_type)
+                    )
+                    course_group.group_type = CourseUserGroup.COHORT
+                    course_group.save()
+                else:
+                    error = True
+                    self.stdout.write(
+                        'CourseUserGroup with an invalid group_type found: {} (type: {})\n'.format(
+                            course_group.name, course_group.group_type)
+                    )
+
+        if not error:
+            self.stdout.write('Ok.\n')
+
+        self.stdout.write('\n### Checking user cohorts\n')
+        error = False
+        users = User.objects.all()
+        _courses = modulestore().get_courses()
+        courses = [c for c in _courses if isinstance(c, CourseDescriptor)]
+        # for each course, check if users are in atleast and only 1 cohort
+        for course in courses:
+            for user in users:
+                if not CourseEnrollment.is_enrolled(user, course.id):
+                    continue
+                try:
+                    CourseUserGroup.objects.get(course_id=course.id,
+                                                users__id=user.id)
+                except CourseUserGroup.DoesNotExist:
+                    if options['fix']:
+                        # create a "default_cohort" is it doesn't already exist
+                        try:
+                            default_cohort = get_cohort_by_name(course.id, CourseUserGroup.default_cohort_name)
+                        except CourseUserGroup.DoesNotExist:
+                            default_cohort = add_cohort(course.id, CourseUserGroup.default_cohort_name)
+                            self.stdout.write('Default cohort "{}" created for course "{}"'.format(
+                                default_cohort.name, course.display_name)
+                            )
+                        add_user_to_cohort(default_cohort, user.username)
+                        self.stdout.write(
+                            'Fixed: User "{}" is not in a cohort in course "{}". Added in "{}" cohort\n'.format(
+                                user.username, course.display_name, default_cohort.name)
+                        )
+                    else:
+                        error = True
+                        self.stdout.write(
+                            'User "{}" is not in a cohort in course "{}".\n'.format(
+                                user.username, course.display_name)
+                        )
+                except MultipleObjectsReturned:
+                    self.stdout.write(
+                        'User "{}" is in multiple cohorts in course "{}".\n'.format(
+                            user.username, course.display_name)
+                    )
+                    if options['fix']:
+                        user_cohorts = CourseUserGroup.objects.filter(course_id=course.id,
+                                                                      users__id=user.id).all()
+                        user_cohort = user_cohorts[0]
+                        for cohort in user_cohorts[1:]:
+                            remove_user_from_cohort(cohort, user.username)
+                            self.stdout.write("User '{}' has been removed from cohort '{}' in course '{}'.\n".format(
+                                user.username, cohort.name, course.display_name)
+                            )
+
+                        self.stdout.write("User '{}' is now only in cohort '{}' in course '{}'.\n".format(
+                            user.username, cohort.name, course.display_name)
+                        )
+                    else:
+                        error = True
+
+        if not error:
+            self.stdout.write('Ok.\n')
+
+        self.stdout.write('\nTo fix issues, run the script with the "--fix" option.\n')

lms/djangoapps/api_manager/users/views.py

@@ -17,6 +17,12 @@ from rest_framework.response import Response
 
 from courseware import grades, module_render
 from courseware.model_data import FieldDataCache
+from openedx.core.djangoapps.course_groups.models import CourseUserGroup
+from openedx.core.djangoapps.course_groups.cohorts import (
+    get_cohort_by_name,
+    add_cohort,
+    add_user_to_cohort
+)
 from django_comment_common.models import Role, FORUM_ROLE_MODERATOR
 from gradebook.models import StudentGradebook
 from instructor.access import revoke_access, update_forum_role
@@ -715,6 +721,15 @@ class UsersCoursesList(SecureAPIView):
             return Response({}, status=status.HTTP_404_NOT_FOUND)
         base_uri = generate_base_uri(request)
         course_enrollment = CourseEnrollment.enroll(user, course_key)
+        # Ensure the user is in a cohort. Add it explicitly in the default_cohort
+        try:
+            default_cohort = get_cohort_by_name(course_id, CourseUserGroup.default_cohort_name)
+        except CourseUserGroup.DoesNotExist:
+            default_cohort = add_cohort(course_id, CourseUserGroup.default_cohort_name)
+        add_user_to_cohort(default_cohort, user.username)
+        log.debug('User "{}" has been automatically added in cohort "{}" for course "{}"'.format(
+            user.username, default_cohort.name, course_descriptor.display_name)
+        )
         response_data['uri'] = '{}/{}'.format(base_uri, course_id)
         response_data['id'] = unicode(course_key)
         response_data['name'] = course_descriptor.display_name

openedx/core/djangoapps/course_groups/models.py

@@ -18,6 +18,8 @@ class CourseUserGroup(models.Model):
     which may be treated specially.  For example, a user can be in at most one cohort per
     course, and cohorts are used to split up the forums by group.
     """
+    default_cohort_name = "default_cohort"
+
     class Meta:
         unique_together = (('name', 'course_id'), )