fix: grant course staff exam access tokens (#359)

* fix: grant course staff exam access tokens

* test: refine tests

* chore: update docstring

edx_exams/apps/api/v1/tests/test_views.py

@@ -654,6 +654,8 @@ def setUp(self):
 
         self.course_id = 'course-v1:edx+test+f19'
 
+        self.user.is_staff = False
+
         self.due_date = timezone.now() + timedelta(minutes=5)
         self.exam = Exam.objects.create(
             resource_id=str(uuid.uuid4()),
@@ -721,8 +723,10 @@ def test_exam_not_found(self):
     def test_access_not_granted(self):
         """
         Verify the endpoint doesn't grant access for an exam
-        without an existing exam attempt or past due date.
+        without an existing exam attempt or past due date
+        while user is not course staff.
         """
+        self.user.is_staff = False
         response = self.get_exam_access(self.user, self.url)
         self.assertEqual(403, response.status_code)
 
@@ -815,6 +819,23 @@ def test_access_no_due_date(self, attempt_status, response_status):
         if response_status == 200:
             self.assert_valid_exam_access_token(response, self.user, no_due_date_exam)
 
+    @ddt.data(
+        (True, 200),
+        (False, 403),
+    )
+    @ddt.unpack
+    def test_access_user_is_course_staff(self, is_course_staff, response_status):
+        """
+        Verify the endpoint immediately grants access
+        for anyone who is course staff.
+        """
+        self.user.is_staff = is_course_staff
+
+        response = self.get_exam_access(self.user, self.url)
+        self.assertEqual(response_status, response.status_code)
+        if response_status == 200:
+            self.assert_valid_exam_access_token(response, self.user, self.exam)
+
     def test_access_not_granted_if_hide_after_due(self):
         """
         Verify the endpoint does not grant access for past-due exam

edx_exams/apps/api/v1/views.py

@@ -318,9 +318,10 @@ class ExamAccessTokensView(ExamsAPIView):
     View to create signed exam access tokens for a specific user and exam.
 
     Given an exam_id and user (in request), this view will either grant access
-    as an exam access token or not grant access. Access is granted if there is an
-    existing exam attempt (must be started if no due date or prior to due date or
-    verified if past the due date.) or if the exam is past its due date.
+    as an exam access token or not grant access. Access is granted if the requesting
+    user is course staff, if there is an existing exam attempt (must be started if
+    no due date or prior to due date or verified if past the due date), or if the
+    exam is past its due date.
 
     HTTP GET
     Provides an Exam Access Token as a cookie if access is granted.
@@ -365,8 +366,12 @@ def get_response(cls, exam, user):
         grant_access = False
         response_status = status.HTTP_403_FORBIDDEN
 
+        # If user is course staff, then grant them access
+        if user.has_course_staff_permission(exam.course_id):
+            grant_access, response_status = True, status.HTTP_200_OK
+
         # If exam attempt exists for user, then grant exam access
-        if exam_attempt is not None:
+        elif exam_attempt is not None:
             # If no due date or if before due date, grant access if attempt started
             # and get expiration window.
             if exam.due_date is None or timezone.now() < exam.due_date: