Make sure that case collisions don't propagate into the CourseOverview data

openedx/core/djangoapps/content/course_overviews/models.py

@@ -40,6 +40,10 @@ from xmodule.tabs import CourseTab
 log = logging.getLogger(__name__)
 
 
+class CourseOverviewCaseMismatchException(Exception):
+    pass
+
+
 @python_2_unicode_compatible
 class CourseOverview(TimeStampedModel):
     """
@@ -167,6 +171,11 @@ class CourseOverview(TimeStampedModel):
         if course_overview.exists():
             log.info(u'Updating course overview for %s.', six.text_type(course.id))
             course_overview = course_overview.first()
+            # MySQL ignores casing, but CourseKey doesn't. To prevent multiple
+            # courses with different cased keys from overriding each other, we'll
+            # check for equality here in python.
+            if course_overview.id != course.id:
+                raise CourseOverviewCaseMismatchException(course_overview.id, course.id)
         else:
             log.info(u'Creating course overview for %s.', six.text_type(course.id))
             course_overview = cls()
@@ -248,8 +257,8 @@ class CourseOverview(TimeStampedModel):
         with store.bulk_operations(course_id):
             course = store.get_course(course_id)
             if isinstance(course, CourseDescriptor):
-                course_overview = cls._create_or_update(course)
                 try:
+                    course_overview = cls._create_or_update(course)
                     with transaction.atomic():
                         course_overview.save()
                         # Remove and recreate all the course tabs