Merge pull request #18657 from open-craft/jill/dont-delete-enrollments

Do not delete course enrollments

common/djangoapps/student/migrations/0016_coursenrollment_course_on_delete_do_nothing.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.14 on 2018-07-27 01:44
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('student', '0015_manualenrollmentaudit_add_role'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='courseenrollment',
+            name='course',
+            field=models.ForeignKey(db_constraint=False, on_delete=django.db.models.deletion.DO_NOTHING, to='course_overviews.CourseOverview'),
+        ),
+    ]

common/djangoapps/student/models.py

@@ -1162,7 +1162,7 @@ class CourseEnrollment(models.Model):
     course = models.ForeignKey(
         CourseOverview,
         db_constraint=False,
-        on_delete=models.CASCADE,
+        on_delete=models.DO_NOTHING,
     )
 
     @property

common/djangoapps/student/tests/test_models.py

@@ -207,6 +207,42 @@ class CourseEnrollmentTests(SharedModuleStoreTestCase):
         self.assertIsNotNone(enrollment.schedule)
         self.assertIsNone(enrollment.upgrade_deadline)
 
+    @skip_unless_lms
+    # NOTE: We mute the post_save signal to prevent Schedules from being created for new enrollments
+    @factory.django.mute_signals(signals.post_save)
+    def test_enrollments_not_deleted(self):
+        """ Recreating a CourseOverview with an outdated version should not delete the associated enrollment. """
+        course = CourseFactory(self_paced=True)
+        CourseModeFactory(
+            course_id=course.id,
+            mode_slug=CourseMode.VERIFIED,
+            # This must be in the future to ensure it is returned by downstream code.
+            expiration_datetime=datetime.datetime.now(pytz.UTC) + datetime.timedelta(days=30),
+        )
+
+        # Create a CourseOverview with an outdated version
+        course_overview = CourseOverview.load_from_module_store(course.id)
+        course_overview.version = CourseOverview.VERSION - 1
+        course_overview.save()
+
+        # Create an inactive enrollment with this course overview
+        enrollment = CourseEnrollmentFactory(
+            user=self.user,
+            course_id=course.id,
+            mode=CourseMode.AUDIT,
+            course=course_overview,
+        )
+
+        # Re-fetch the CourseOverview record.
+        # As a side effect, this will recreate the record, and update the version.
+        course_overview_new = CourseOverview.get_from_id(course.id)
+        self.assertEqual(course_overview_new.version, CourseOverview.VERSION)
+
+        # Ensure that the enrollment record was unchanged during this re-creation
+        enrollment_refetched = CourseEnrollment.objects.filter(id=enrollment.id)
+        self.assertTrue(enrollment_refetched.exists())
+        self.assertEqual(enrollment_refetched.all()[0], enrollment)
+
 
 class PendingNameChangeTests(SharedModuleStoreTestCase):
     """