When deleting the solution to a question, set the question solution to None (bug 585313)

apps/questions/models.py

@@ -287,13 +287,16 @@ class Answer(ModelBase):
     def delete(self, *args, **kwargs):
         """Override delete method to update parent question info."""
         question = Question.uncached.get(pk=self.question.id)
-        if question.last_answer and question.last_answer == self:
+        if question.last_answer == self:
             answers = question.answers.all().order_by('-created')
             try:
                 question.last_answer = answers[1]
             except IndexError:
                 # The question has only one answer
                 question.last_answer = None
+        if question.solution == self:
+            question.solution = None
+
         question.num_answers = question.answers.count() - 1
         question.save()
 

apps/questions/tests/test_models.py

@@ -57,6 +57,20 @@ class TestAnswer(TestCaseBase):
         eq_(question.last_answer.id, last_answer.id)
         eq_(Answer.objects.filter(pk=answer.id).count(), 0)
 
+    def test_delete_solution_of_question(self):
+        """Deleting the solution of a Question should update the question.
+        """
+        # set a solution to the question
+        question = Question.objects.all()[0]
+        solution = question.last_answer
+        question.solution = solution
+        question.save()
+
+        # delete the solution and question.solution should go back to None
+        solution.delete()
+        question = Question.objects.get(pk=question.id)
+        eq_(question.solution, None)
+
     def test_creator_num_posts(self):
         """Test retrieval of post count for creator of a particular answer"""
         question = Question.objects.all()[0]