Switching course view to specific student retains the profile language setting

https://openedx.atlassian.net/browse/EDUCATOR-891

lms/djangoapps/courseware/tests/test_masquerade.py

@@ -5,6 +5,7 @@ import json
 import pickle
 from datetime import datetime
 
+from django.conf import settings
 from django.core.urlresolvers import reverse
 from django.test import TestCase
 from django.utils.timezone import UTC
@@ -17,13 +18,16 @@ from courseware.masquerade import (
     CourseMasquerade,
     MasqueradingKeyValueStore,
     get_masquerading_user_group,
-    handle_ajax,
-    setup_masquerade
 )
 from courseware.tests.factories import StaffFactory
 from courseware.tests.helpers import LoginEnrollmentTestCase, masquerade_as_group_member
 from courseware.tests.test_submitting_problems import ProblemSubmissionTestMixin
+from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY
 from openedx.core.djangoapps.self_paced.models import SelfPacedConfiguration
+from openedx.core.djangoapps.user_api.preferences.api import (
+    get_user_preference,
+    set_user_preference
+)
 from student.tests.factories import UserFactory
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.tests.django_utils import SharedModuleStoreTestCase
@@ -311,6 +315,22 @@ class TestStaffMasqueradeAsSpecificStudent(StaffMasqueradeTestCase, ProblemSubmi
         progress = '%s/%s' % (str(json_data['current_score']), str(json_data['total_possible']))
         return progress
 
+    def assertExpectedLanguageInPreference(self, user, expected_language_code):
+        """
+        This method is a custom assertion verifies that a given user has expected
+        language code in the preference and in cookies.
+
+        Arguments:
+            user: User model instance
+            expected_language_code: string indicating a language code
+        """
+        self.assertEqual(
+            get_user_preference(user, LANGUAGE_KEY), expected_language_code
+        )
+        self.assertEqual(
+            self.client.cookies[settings.LANGUAGE_COOKIE].value, expected_language_code
+        )
+
     @patch.dict('django.conf.settings.FEATURES', {'DISABLE_START_DATES': False})
     def test_masquerade_as_specific_user_on_self_paced(self):
         """
@@ -375,6 +395,31 @@ class TestStaffMasqueradeAsSpecificStudent(StaffMasqueradeTestCase, ProblemSubmi
         self.login_student()
         self.assertEqual(self.get_progress_detail(), u'2/2')
 
+    def test_masquerading_with_language_preference(self):
+        """
+        Tests that masquerading as a specific user for the course does not update preference language
+        for the staff.
+
+        Login as a staff user and set user's language preference to english and visit the courseware page.
+        Set masquerade to view same page as a specific student having different language preference and
+        revisit the courseware page.
+        """
+        english_language_code = 'en'
+        set_user_preference(self.test_user, preference_key=LANGUAGE_KEY, preference_value=english_language_code)
+        self.login_staff()
+
+        # Reload the page and check we have expected language preference in system and in cookies.
+        self.get_courseware_page()
+        self.assertExpectedLanguageInPreference(self.test_user, english_language_code)
+
+        # Set student language preference and set masquerade to view same page the student.
+        set_user_preference(self.student_user, preference_key=LANGUAGE_KEY, preference_value='es-419')
+        self.update_masquerade(role='student', user_name=self.student_user.username)
+
+        # Reload the page and check we have expected language preference in system and in cookies.
+        self.get_courseware_page()
+        self.assertExpectedLanguageInPreference(self.test_user, english_language_code)
+
     @patch.dict('django.conf.settings.FEATURES', {'DISABLE_START_DATES': False})
     def test_masquerade_as_specific_student_course_info(self):
         """

openedx/core/djangoapps/lang_pref/middleware.py

@@ -5,11 +5,11 @@ Middleware for Language Preferences
 from django.conf import settings
 from django.utils.translation import LANGUAGE_SESSION_KEY
 from django.utils.translation.trans_real import parse_accept_lang_header
+from lms.djangoapps.courseware.masquerade import MASQUERADE_SETTINGS_KEY
 
 from openedx.core.djangoapps.lang_pref import COOKIE_DURATION, LANGUAGE_HEADER, LANGUAGE_KEY
 from openedx.core.djangoapps.user_api.errors import UserAPIInternalError, UserAPIRequestError
 from openedx.core.djangoapps.user_api.preferences.api import (
-    delete_user_preference,
     get_user_preference,
     set_user_preference
 )
@@ -51,18 +51,22 @@ class LanguagePreferenceMiddleware(object):
                 del request.session[LANGUAGE_SESSION_KEY]
 
     def process_response(self, request, response):
-        # If the user is logged in, check for their language preference
-        if getattr(request, 'user', None) and request.user.is_authenticated():
-            user_pref = None
+        # If the user is logged in, check for their language preference. Also check for real user
+        # if current user is a masquerading user,
+        user_pref = None
+        current_user = None
+        if hasattr(request, 'user'):
+            current_user = getattr(request.user, 'real_user', request.user)
 
+        if current_user and current_user.is_authenticated():
             anonymous_cookie_lang = getattr(request, '_anonymous_user_cookie_lang', None)
             if anonymous_cookie_lang:
                 user_pref = anonymous_cookie_lang
-                set_user_preference(request.user, LANGUAGE_KEY, anonymous_cookie_lang)
+                set_user_preference(current_user, LANGUAGE_KEY, anonymous_cookie_lang)
             else:
                 # Get the user's language preference
                 try:
-                    user_pref = get_user_preference(request.user, LANGUAGE_KEY)
+                    user_pref = get_user_preference(current_user, LANGUAGE_KEY)
                 except (UserAPIRequestError, UserAPIInternalError):
                     # If we can't find the user preferences, then don't modify the cookie
                     pass