Exclude unscored homeworks from dashboard difficulty stats

The Question difficulty and Assignment difficulty sections on the course
dashboard were computing stats from Answer.is_correct and
Submission.questions_score for all homeworks, including unscored ones.
Unscored homeworks have is_correct=False and questions_score=0 by
default, so they showed 0 correct answers and 0% scores — misleading
data that looked like real difficulty metrics.

Now both sections filter to only include homeworks in the SCORED state.

Author: alexeygrigorev

courses/tests/test_dashboard_homework_difficulty.py

@@ -1,5 +1,6 @@
 from django.urls import reverse
 
+from courses.models import HomeworkState
 from courses.tests.dashboard_homework_base import (
     DashboardHomeworkStatsTestBase,
 )
@@ -8,11 +9,15 @@
 class DashboardHomeworkDifficultyTestCase(DashboardHomeworkStatsTestBase):
     def test_homework_difficulty_ranking(self):
         self.add_questions(self.homework, 3)
+        self.homework.state = HomeworkState.SCORED.value
+        self.homework.save()
         harder_homework = self.create_homework_for_difficulty(
             "hw2",
             "Homework 2",
             14,
         )
+        harder_homework.state = HomeworkState.SCORED.value
+        harder_homework.save()
         self.add_questions(harder_homework, 10)
         self.create_difficulty_submissions(harder_homework)
 
@@ -22,3 +27,25 @@ def test_homework_difficulty_ranking(self):
         self.assert_difficulty_ranking(response, harder_homework)
         self.assertContains(response, "Assignment difficulty")
         self.assertContains(response, "Completion")
+
+    def test_difficulty_excludes_unscored_homework(self):
+        self.add_questions(self.homework, 3)
+        self.homework.state = HomeworkState.SCORED.value
+        self.homework.save()
+        unscored = self.create_homework_for_difficulty(
+            "hw2",
+            "Homework 2",
+            14,
+        )
+        self.add_questions(unscored, 3)
+        self.create_difficulty_submissions(unscored)
+
+        url = reverse("dashboard", args=[self.course.slug])
+        response = self.client.get(url)
+
+        difficulty_stats = response.context["homework_difficulty_stats"]
+        homework_titles = [
+            hw_stat["homework"].title for hw_stat in difficulty_stats
+        ]
+        self.assertIn("Homework 1", homework_titles)
+        self.assertNotIn("Homework 2", homework_titles)

courses/tests/test_dashboard_question_difficulty.py

@@ -113,3 +113,47 @@ def test_question_difficulty_empty_without_answers(self):
 
         self.assertEqual(response.context["question_difficulty"], [])
         self.assertNotContains(response, "Question difficulty")
+
+    def test_question_difficulty_excludes_unscored_homework(self):
+        self.create_answers([True, False])
+
+        unscored = Homework.objects.create(
+            course=self.course,
+            slug="hw2",
+            title="Homework 2",
+            due_date=timezone.now() + timedelta(days=14),
+            state=HomeworkState.OPEN.value,
+        )
+        unscored_question = Question.objects.create(
+            homework=unscored,
+            text="Unscored question?",
+            question_type=QuestionTypes.MULTIPLE_CHOICE.value,
+            answer_type=AnswerTypes.INTEGER.value,
+            scores_for_correct_answer=1,
+        )
+        user = User.objects.create_user(
+            username="unscored_student@test.com",
+            email="unscored_student@test.com",
+            password="12345",
+        )
+        enrollment = Enrollment.objects.create(
+            student=user, course=self.course
+        )
+        submission = Submission.objects.create(
+            homework=unscored,
+            student=user,
+            enrollment=enrollment,
+        )
+        Answer.objects.create(
+            submission=submission,
+            question=unscored_question,
+            answer_text="1",
+            is_correct=False,
+        )
+
+        response = self.client.get(self.dashboard_url())
+
+        groups = response.context["question_difficulty"]
+        homework_titles = [g["homework_title"] for g in groups]
+        self.assertIn("Homework 1", homework_titles)
+        self.assertNotIn("Homework 2", homework_titles)

courses/views/dashboard_homeworks.py

@@ -3,7 +3,7 @@
 
 from django.db.models import Sum
 
-from courses.models.homework import Homework, Submission
+from courses.models.homework import Homework, HomeworkState, Submission
 from courses.views.dashboard_metrics import (
     quartile_fields,
     safe_quartiles,
@@ -188,7 +188,11 @@ def _homework_difficulty_sort_key(hw_stat):
 def dashboard_homework_difficulty_stats(homework_stats):
     difficulty_stats = []
     for hw_stat in homework_stats:
-        if hw_stat["score_ratio"] is not None:
+        homework = hw_stat["homework"]
+        if (
+            hw_stat["score_ratio"] is not None
+            and homework.state == HomeworkState.SCORED.value
+        ):
             difficulty_stats.append(hw_stat)
     difficulty_stats.sort(key=_homework_difficulty_sort_key)
     for rank, hw_stat in enumerate(difficulty_stats, start=1):

courses/views/dashboard_questions.py

@@ -1,6 +1,6 @@
 from django.db.models import Count, Q
 
-from courses.models.homework import Answer, AnswerTypes
+from courses.models.homework import Answer, AnswerTypes, HomeworkState
 
 
 def dashboard_question_difficulty(course):
@@ -13,6 +13,7 @@ def dashboard_question_difficulty(course):
     rows = (
         Answer.objects
         .filter(question__homework__course=course)
+        .filter(question__homework__state=HomeworkState.SCORED.value)
         .exclude(question__answer_type=AnswerTypes.ANY.value)
         .values(
             "question_id",