Add masquerading feature for preview mode

lms/djangoapps/courseware/access.py

@@ -136,8 +136,9 @@ def has_access(user, action, obj, course_key=None):
     if not user:
         user = AnonymousUser()
 
-    if in_preview_mode():
-        if not bool(has_staff_access_to_preview_mode(user=user, obj=obj, course_key=course_key)):
+    # Preview mode is only accessible by staff.
+    if in_preview_mode() and course_key:
+        if not has_staff_access_to_preview_mode(user, course_key):
             return ACCESS_DENIED
 
     # delegate the work to type-specific functions.
@@ -173,51 +174,14 @@ def has_access(user, action, obj, course_key=None):
                     .format(type(obj)))
 
 
-# ================ Implementation helpers ================================
-
-def has_staff_access_to_preview_mode(user, obj, course_key=None):
+def has_staff_access_to_preview_mode(user, course_key):
     """
-    Returns whether user has staff access to specified modules or not.
-
-    Arguments:
-
-        user: a Django user object.
-
-        obj: The object to check access for.
-
-        course_key: A course_key specifying which course this access is for.
-
-    Returns an AccessResponse object.
+    Checks if given user can access course in preview mode.
+    A user can access a course in preview mode only if User has staff access to course.
     """
-    if course_key is None:
-        if isinstance(obj, CourseDescriptor) or isinstance(obj, CourseOverview):
-            course_key = obj.id
-
-        elif isinstance(obj, ErrorDescriptor):
-            course_key = obj.location.course_key
-
-        elif isinstance(obj, XModule):
-            course_key = obj.descriptor.course_key
-
-        elif isinstance(obj, XBlock):
-            course_key = obj.location.course_key
+    has_admin_access_to_course = any(administrative_accesses_to_course_for_user(user, course_key))
 
-        elif isinstance(obj, CCXLocator):
-            course_key = obj.to_course_locator()
-
-        elif isinstance(obj, CourseKey):
-            course_key = obj
-
-        elif isinstance(obj, UsageKey):
-            course_key = obj.course_key
-
-    if course_key is None:
-        if GlobalStaff().has_user(user):
-            return ACCESS_GRANTED
-        else:
-            return ACCESS_DENIED
-
-    return _has_access_to_course(user, 'staff', course_key=course_key)
+    return has_admin_access_to_course or is_masquerading_as_student(user, course_key)
 
 
 def _can_access_descriptor_with_start_date(user, descriptor, course_key):  # pylint: disable=invalid-name
@@ -733,10 +697,12 @@ def _has_access_to_course(user, access_level, course_key):
         debug("Deny: no user or anon user")
         return ACCESS_DENIED
 
-    if not in_preview_mode() and is_masquerading_as_student(user, course_key):
+    if is_masquerading_as_student(user, course_key):
         return ACCESS_DENIED
 
-    if GlobalStaff().has_user(user):
+    global_staff, staff_access, instructor_access = administrative_accesses_to_course_for_user(user, course_key)
+
+    if global_staff:
         debug("Allow: user.is_staff")
         return ACCESS_GRANTED
 
@@ -745,19 +711,10 @@ def _has_access_to_course(user, access_level, course_key):
         debug("Deny: unknown access level")
         return ACCESS_DENIED
 
-    staff_access = (
-        CourseStaffRole(course_key).has_user(user) or
-        OrgStaffRole(course_key.org).has_user(user)
-    )
     if staff_access and access_level == 'staff':
         debug("Allow: user has course staff access")
         return ACCESS_GRANTED
 
-    instructor_access = (
-        CourseInstructorRole(course_key).has_user(user) or
-        OrgInstructorRole(course_key.org).has_user(user)
-    )
-
     if instructor_access and access_level in ('staff', 'instructor'):
         debug("Allow: user has course instructor access")
         return ACCESS_GRANTED
@@ -766,6 +723,25 @@ def _has_access_to_course(user, access_level, course_key):
     return ACCESS_DENIED
 
 
+def administrative_accesses_to_course_for_user(user, course_key):
+    """
+    Returns types of access a user have for given course.
+    """
+    global_staff = GlobalStaff().has_user(user)
+
+    staff_access = (
+        CourseStaffRole(course_key).has_user(user) or
+        OrgStaffRole(course_key.org).has_user(user)
+    )
+
+    instructor_access = (
+        CourseInstructorRole(course_key).has_user(user) or
+        OrgInstructorRole(course_key.org).has_user(user)
+    )
+
+    return global_staff, staff_access, instructor_access
+
+
 def _has_instructor_access_to_descriptor(user, descriptor, course_key):  # pylint: disable=invalid-name
     """Helper method that checks whether the user has staff access to
     the course of the location.

lms/djangoapps/courseware/tests/test_access.py

@@ -199,44 +199,41 @@ class AccessTestCase(LoginEnrollmentTestCase, ModuleStoreTestCase, MilestonesTes
 
     def test_has_staff_access_to_preview_mode(self):
         """
-        Tests users have right access to content in preview mode.
+        Test that preview mode is only accessible by staff users.
         """
         course_key = self.course.id
-        usage_key = self.course.scope_ids.usage_id
-        chapter = ItemFactory.create(category="chapter", parent_location=self.course.location)
-        overview = CourseOverview.get_from_id(course_key)
-        test_system = get_test_system()
+        CourseEnrollmentFactory(user=self.student, course_id=self.course.id)
 
-        ccx = CcxFactory(course_id=course_key)
-        ccx_locator = CCXLocator.from_course_locator(course_key, ccx.id)
+        for user in [self.global_staff, self.course_staff, self.course_instructor]:
+            self.assertTrue(access.has_staff_access_to_preview_mode(user, course_key))
 
-        error_descriptor = ErrorDescriptor.from_xml(
-            u"<problem>ABC \N{SNOWMAN}</problem>",
-            test_system,
-            CourseLocationManager(course_key),
-            "error msg"
-        )
-        # Enroll student to the course
-        CourseEnrollmentFactory(user=self.student, course_id=self.course.id)
+        self.assertFalse(access.has_staff_access_to_preview_mode(self.student, course_key))
 
-        modules = [
-            self.course,
-            overview,
-            chapter,
-            ccx_locator,
-            error_descriptor,
-            course_key,
-            usage_key,
-        ]
-        # Course key is not None
-        self.assertTrue(
-            bool(access.has_staff_access_to_preview_mode(self.global_staff, obj=self.course, course_key=course_key))
-        )
+        # we don't want to restrict a staff user, masquerading as student,
+        # to access preview mode.
 
-        for user in [self.global_staff, self.course_staff, self.course_instructor]:
-            for obj in modules:
-                self.assertTrue(bool(access.has_staff_access_to_preview_mode(user, obj=obj)))
-                self.assertFalse(bool(access.has_staff_access_to_preview_mode(self.student, obj=obj)))
+        # Note that self.student now have access to preview mode,
+        # `is_masquerading_as_student == True` means user is staff and is
+        # masquerading as a student.
+        with patch('courseware.access.is_masquerading_as_student') as mock_masquerade:
+            mock_masquerade.return_value = True
+            for user in [self.global_staff, self.course_staff, self.course_instructor, self.student]:
+                self.assertTrue(access.has_staff_access_to_preview_mode(user, course_key))
+
+    def test_administrative_accesses_to_course_for_user(self):
+        """
+        Test types of admin accesses to a course
+        """
+        course_key = self.course.id
+
+        # `administrative_accesses_to_course_for_user` returns accesses in tuple as
+        # (`global_staff`, `course_staff`, `course_instructor`).
+        # Order matters here, for example `True` at first index in tuple essentially means
+        # given user is a global staff.
+        for count, user in enumerate([self.global_staff, self.course_staff, self.course_instructor]):
+            self.assertTrue(access.administrative_accesses_to_course_for_user(user, course_key)[count])
+
+        self.assertFalse(any(access.administrative_accesses_to_course_for_user(self.student, course_key)))
 
     def test_student_has_access(self):
         """
@@ -264,15 +261,6 @@ class AccessTestCase(LoginEnrollmentTestCase, ModuleStoreTestCase, MilestonesTes
             for obj in modules:
                 self.assertFalse(bool(access.has_access(self.student, 'load', obj, course_key=self.course.id)))
 
-    def test_string_has_staff_access_to_preview_mode(self):
-        """
-        Tests different users has right access to string content in preview mode.
-        """
-        self.assertTrue(bool(access.has_staff_access_to_preview_mode(self.global_staff, obj='global')))
-        self.assertFalse(bool(access.has_staff_access_to_preview_mode(self.course_staff, obj='global')))
-        self.assertFalse(bool(access.has_staff_access_to_preview_mode(self.course_instructor, obj='global')))
-        self.assertFalse(bool(access.has_staff_access_to_preview_mode(self.student, obj='global')))
-
     @patch('courseware.access.in_preview_mode', Mock(return_value=True))
     def test_has_access_with_preview_mode(self):
         """
@@ -286,17 +274,17 @@ class AccessTestCase(LoginEnrollmentTestCase, ModuleStoreTestCase, MilestonesTes
         self.assertFalse(bool(access.has_access(self.student, 'staff', self.course, course_key=self.course.id)))
         self.assertFalse(bool(access.has_access(self.student, 'load', self.course, course_key=self.course.id)))
 
-        # User should be able to preview when masquerade.
+        # When masquerading is true, user should not be able to access staff content
         with patch('courseware.access.is_masquerading_as_student') as mock_masquerade:
             mock_masquerade.return_value = True
-            self.assertTrue(
+            self.assertFalse(
                 bool(access.has_access(self.global_staff, 'staff', self.course, course_key=self.course.id))
             )
             self.assertFalse(
                 bool(access.has_access(self.student, 'staff', self.course, course_key=self.course.id))
             )
 
-    @patch('courseware.access.in_preview_mode', Mock(return_value=True))
+    @patch('courseware.access_utils.in_preview_mode', Mock(return_value=True))
     def test_has_access_in_preview_mode_with_group(self):
         """
         Test that a user masquerading as a member of a group sees appropriate content in preview mode.
@@ -851,7 +839,10 @@ class CourseOverviewAccessTestCase(ModuleStoreTestCase):
             user = getattr(self, user_attr_name)
             user = User.objects.get(id=user.id)
 
-        if user_attr_name == 'user_staff' and action == 'see_exists' and course_attr_name == 'course_not_started':
+        if (user_attr_name == 'user_staff' and
+            action == 'see_exists' and
+            course_attr_name in
+                ['course_default', 'course_not_started']):
             # checks staff role
             num_queries = 1
         elif user_attr_name == 'user_normal' and action == 'see_exists' and course_attr_name != 'course_started':