fix: don't count hierarchy blocks as complete for assignments

When considering whether a subsection is complete as an assignment,
skip any "hierarchy" types (sequential, vertical, etc) that don't
have children. If the user can't see the content, don't risk
marking it as complete.

AA-726

lms/djangoapps/courseware/tests/test_courses.py

@@ -443,3 +443,17 @@ class TestGetCourseAssignments(CompletionWaffleTestMixin, ModuleStoreTestCase):
         assignments = get_course_assignments(course.location.context_key, self.user, None)
         assert len(assignments) == 1
         assert assignments[0].complete
+
+    def test_completion_does_not_count_empty_sequentials(self):
+        """
+        Test that we treat a sequential with no content as incomplete.
+
+        This can happen with unreleased assignments, for example (start date in future).
+        """
+        course = CourseFactory()
+        chapter = ItemFactory(parent=course, category='chapter', graded=True, due=datetime.datetime.now())
+        ItemFactory(parent=chapter, category='sequential')
+
+        assignments = get_course_assignments(course.location.context_key, self.user, None)
+        assert len(assignments) == 1
+        assert not assignments[0].complete

openedx/features/course_experience/utils.py

@@ -214,6 +214,15 @@ def is_block_structure_complete_for_assignments(block_data, block_key):
     if children:
         return all(is_block_structure_complete_for_assignments(block_data, child_key) for child_key in children)
 
+    category = block_data.get_xblock_field(block_key, 'category')
+    if category in ('course', 'chapter', 'sequential', 'vertical'):
+        # If there are no children for these "hierarchy" block types, just bail. This could be because the
+        # content isn't available yet (start date in future) or we're too late and the block has hide_after_due
+        # set. Or maybe a different transformer cut off content for whatever reason. Regardless of the cause - if the
+        # user can't see this content and we continue, we might accidentally say this block is complete because it
+        # isn't scored (which most hierarchy blocks wouldn't be).
+        return False
+
     complete = block_data.get_xblock_field(block_key, 'complete', False)
     graded = block_data.get_xblock_field(block_key, 'graded', False)
     has_score = block_data.get_xblock_field(block_key, 'has_score', False)