fix: Return unmigrated rows for subsection_and_higher_only

The call to get_dates_for_course would previously not return unmigrated
ContentDates when subsection_and_higher_only=True, because it was
scanning for equality to block_type=None as a fallback, when in SQL
None != None, and has to be queried for explicitly with isnull in the
Django ORM. TNL-8061

CHANGELOG.rst

@@ -14,6 +14,10 @@ Change Log
 Unreleased
 ~~~~~~~~~~
 
+[2.2.1] - 2021-09-15
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+* Bug fix for optimization in 2.2.0, to account for missing block_type data.
+
 [2.2.0] - 2021-08-27
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Added optimization when requesting course block dates for an outline, where block dates below subsections are unneeded.

edx_when/__init__.py

@@ -2,6 +2,6 @@
 Central source of course block dates for the LMS.
 """
 
-__version__ = '2.2.0'
+__version__ = '2.2.1'
 
 default_app_config = 'edx_when.apps.EdxWhenConfig'  # pylint: disable=invalid-name

edx_when/api.py

@@ -151,7 +151,8 @@ def _processed_results_cache_key(
     if allow_relative_dates:
         cache_key += '.with-rel-dates'
     if subsection_and_higher_only:
-        cache_key += '.subsection_and_higher_only'
+        # cache key incremented with ".v2" so we don't mix buggy cached data with fixed data
+        cache_key += '.subsection_and_higher_only.v2'
     cache_key += '.%s' % published_version if published_version else ''
     return cache_key
 
@@ -222,7 +223,10 @@ def get_dates_for_course(
         qset = models.ContentDate.objects.filter(course_id=course_id, active=True, **rel_lookup)
         if subsection_and_higher_only:
             # Include NULL block_type values as well because of lazy rollout.
-            qset = qset.filter(Q(block_type__in=('course', 'chapter', 'sequential', None)))
+            qset = qset.filter(
+                Q(block_type__in=('course', 'chapter', 'sequential')) |
+                Q(block_type__isnull=True)
+            )
 
         qset = list(
             qset.select_related('policy')

tests/test_api.py

@@ -142,6 +142,20 @@ def test_get_dates_for_course_outline(self):
         )
         assert len(retrieved) == NUM_OVERRIDES
 
+        # Set all the ContentDates for this course's structural blocks to have
+        # None for their block_type to test compatibilty with a half-migrated
+        # state. They should still be returned by get_dates_for_course with
+        # subsection_and_higher_only=True.
+        structural_dates = models.ContentDate.objects.filter(
+            course_id=course_key,
+            block_type__in=['course', 'chapter', 'sequential']
+        )
+        structural_dates.update(block_type=None)
+        retrieved = api.get_dates_for_course(
+            course_key, subsection_and_higher_only=True, published_version=self.course_version, use_cached=False
+        )
+        assert len(retrieved) == NUM_OVERRIDES
+
     def test_get_dates_for_course(self):
         items = make_items()
         api.set_dates_for_course(items[0][0].course_key, items)