Store Learner language preferences into a cookie rather than the session

This modifies the lang-pref django app to:
a) Use the current value of the 'edx-language-preference' cookie to set the
   users Accept-Language header on an incoming request.
b) At the end of the request, update the 'edx-language-preference' cookie
   to reflect the users current Language Preference choice, if any.

[LEARNER-542]

common/djangoapps/student/cookies.py

@@ -17,7 +17,7 @@ from student.models import CourseEnrollment
 CREATE_LOGON_COOKIE = Signal(providing_args=['user', 'response'])
 
 
-def _get_cookie_settings(request):
+def standard_cookie_settings(request):
     """ Returns the common cookie settings (e.g. expiration time). """
 
     if request.session.get_expire_at_browser_close():
@@ -73,7 +73,7 @@ def set_logged_in_cookies(request, response, user):
         HttpResponse
 
     """
-    cookie_settings = _get_cookie_settings(request)
+    cookie_settings = standard_cookie_settings(request)
 
     # Backwards compatibility: set the cookie indicating that the user
     # is logged in.  This is just a boolean value, so it's not very useful.
@@ -96,7 +96,7 @@ def set_logged_in_cookies(request, response, user):
 
 def set_user_info_cookie(response, request):
     """ Sets the user info cookie on the response. """
-    cookie_settings = _get_cookie_settings(request)
+    cookie_settings = standard_cookie_settings(request)
 
     # In production, TLS should be enabled so that this cookie is encrypted
     # when we send it.  We also need to set "secure" to True so that the browser

lms/djangoapps/courseware/tests/test_course_info.py

@@ -367,7 +367,7 @@ class SelfPacedCourseInfoTestCase(LoginEnrollmentTestCase, SharedModuleStoreTest
         self.assertEqual(resp.status_code, 200)
 
     def test_num_queries_instructor_paced(self):
-        self.fetch_course_info_with_queries(self.instructor_paced_course, 21, 4)
+        self.fetch_course_info_with_queries(self.instructor_paced_course, 24, 4)
 
     def test_num_queries_self_paced(self):
-        self.fetch_course_info_with_queries(self.self_paced_course, 21, 4)
+        self.fetch_course_info_with_queries(self.self_paced_course, 24, 4)

lms/djangoapps/courseware/tests/test_i18n.py

@@ -2,6 +2,7 @@
 Tests i18n in courseware
 """
 
+import json
 import re
 
 from django.conf import settings
@@ -14,7 +15,6 @@ from nose.plugins.attrib import attr
 
 from openedx.core.djangoapps.dark_lang.models import DarkLangConfig
 from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY
-from openedx.core.djangoapps.user_api.preferences.api import set_user_preference
 from student.models import UserProfile
 from student.tests.factories import UserFactory
 
@@ -175,6 +175,15 @@ class I18nLangPrefTests(BaseI18nTestCase):
         UserProfile.objects.create(user=self.user)
         self.user_login()
 
+    def set_lang_preference(self, language):
+        """Sets the user's language preference, allowing the LangPref middleware to operate to set the preference cookie."""
+        response = self.client.patch(
+            reverse('preferences_api', args=[self.user.username]),
+            json.dumps({LANGUAGE_KEY: language}),
+            content_type="application/merge-patch+json"
+        )
+        self.assertEqual(response.status_code, 204)
+
     def test_lang_preference(self):
         # Regression test; LOC-87
         self.release_languages('ar, es-419')
@@ -184,13 +193,13 @@ class I18nLangPrefTests(BaseI18nTestCase):
         self.assert_tag_has_attr(response.content, "html", "lang", self.site_lang)
 
         # Set user language preference
-        set_user_preference(self.user, LANGUAGE_KEY, 'ar')
+        self.set_lang_preference('ar')
         # and verify we now get an ar response
         response = self.client.get(self.url)
         self.assert_tag_has_attr(response.content, "html", "lang", 'ar')
 
         # Verify that switching language preference gives the right language
-        set_user_preference(self.user, LANGUAGE_KEY, 'es-419')
+        self.set_lang_preference('es-419')
         response = self.client.get(self.url)
         self.assert_tag_has_attr(response.content, "html", "lang", 'es-419')
 
@@ -199,7 +208,7 @@ class I18nLangPrefTests(BaseI18nTestCase):
         self.release_languages('ar, es-419')
 
         # Set user language preference
-        set_user_preference(self.user, LANGUAGE_KEY, 'ar')
+        self.set_lang_preference('ar')
         # Verify preview-lang takes precedence
         self.client.post(self.preview_language_url, {'preview_lang': 'eo', 'set_language': 'set_language'})
         response = self.client.get(self.url)

lms/envs/devstack_docker.py

@@ -30,6 +30,7 @@ FEATURES.update({
     'ENABLE_COURSEWARE_SEARCH': False,
     'ENABLE_COURSE_DISCOVERY': False,
     'ENABLE_DASHBOARD_SEARCH': False,
+    'SHOW_LANGUAGE_SELECTOR': True
 })
 
 ENABLE_MKTG_SITE = os.environ.get('ENABLE_MARKETING_SITE', False)

openedx/core/djangoapps/lang_pref/__init__.py

@@ -4,3 +4,9 @@ Useful information for setting the language preference
 
 # this is the UserPreference key for the user's preferred language
 LANGUAGE_KEY = 'pref-lang'
+
+LANGUAGE_COOKIE = 'edx-language-preference'
+
+LANGUAGE_HEADER = 'HTTP_ACCEPT_LANGUAGE'
+
+COOKIE_DURATION = 14 * 24 * 60 * 60  # 14 days in seconds

openedx/core/djangoapps/lang_pref/middleware.py

@@ -2,12 +2,17 @@
 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 openedx.core.djangoapps.lang_pref import LANGUAGE_KEY
-from openedx.core.djangoapps.lang_pref.api import released_languages
-from openedx.core.djangoapps.user_api.preferences.api import get_user_preference, delete_user_preference
+from openedx.core.djangoapps.lang_pref import (
+    LANGUAGE_KEY, LANGUAGE_COOKIE, LANGUAGE_HEADER, COOKIE_DURATION
+)
+from openedx.core.djangoapps.user_api.preferences.api import (
+    get_user_preference, delete_user_preference, set_user_preference
+)
+from openedx.core.djangoapps.user_api.errors import UserAPIInternalError, UserAPIRequestError
 
 
 class LanguagePreferenceMiddleware(object):
@@ -21,17 +26,46 @@ class LanguagePreferenceMiddleware(object):
     def process_request(self, request):
         """
         If a user's UserPreference contains a language preference, use the user's preference.
+        Save the current language preference cookie as the user's preferred language.
         """
-        languages = released_languages()
-        system_released_languages = [seq[0] for seq in languages]
+        cookie_lang = request.COOKIES.get(LANGUAGE_COOKIE, None)
+        if cookie_lang:
+            if request.user.is_authenticated():
+                set_user_preference(request.user, LANGUAGE_KEY, cookie_lang)
 
+            accept_header = request.META.get(LANGUAGE_HEADER, None)
+            if accept_header:
+                current_langs = parse_accept_lang_header(accept_header)
+                # Promote the cookie_lang over any language currently in the accept header
+                current_langs = [(lang, qvalue) for (lang, qvalue) in current_langs if lang != cookie_lang]
+                current_langs.insert(0, (cookie_lang, 1))
+                accept_header = ",".join("{};q={}".format(lang, qvalue) for (lang, qvalue) in current_langs)
+            else:
+                accept_header = cookie_lang
+            request.META[LANGUAGE_HEADER] = accept_header
+
+    def process_response(self, request, response):
         # If the user is logged in, check for their language preference
-        if request.user.is_authenticated():
+        if getattr(request, 'user', None) and request.user.is_authenticated():
             # Get the user's language preference
-            user_pref = get_user_preference(request.user, LANGUAGE_KEY)
-            # Set it to the LANGUAGE_SESSION_KEY (Django-specific session setting governing language pref)
-            if user_pref:
-                if user_pref in system_released_languages:
-                    request.session[LANGUAGE_SESSION_KEY] = user_pref
+            try:
+                user_pref = get_user_preference(request.user, LANGUAGE_KEY)
+            except (UserAPIRequestError, UserAPIInternalError):
+                # If we can't find the user preferences, then don't modify the cookie
+                pass
+            else:
+                # Set it in the LANGUAGE_COOKIE
+                if user_pref:
+                    response.set_cookie(
+                        LANGUAGE_COOKIE,
+                        value=user_pref,
+                        domain=settings.SESSION_COOKIE_DOMAIN,
+                        max_age=COOKIE_DURATION,
+                    )
                 else:
-                    delete_user_preference(request.user, LANGUAGE_KEY)
+                    response.delete_cookie(
+                        LANGUAGE_COOKIE,
+                        domain=settings.SESSION_COOKIE_DOMAIN
+                    )
+
+        return response

openedx/core/djangoapps/lang_pref/tests/test_middleware.py

@@ -2,17 +2,21 @@
 Tests for lang_pref middleware.
 """
 
+import itertools
 import mock
 
 import ddt
+from django.conf import settings
 from django.test import TestCase
 from django.test.client import RequestFactory
+from django.http import HttpResponse
 from django.contrib.sessions.middleware import SessionMiddleware
 from django.utils.translation import LANGUAGE_SESSION_KEY
+from django.utils.translation.trans_real import parse_accept_lang_header
 
-from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY
+from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY, LANGUAGE_COOKIE, COOKIE_DURATION
 from openedx.core.djangoapps.lang_pref.middleware import LanguagePreferenceMiddleware
-from openedx.core.djangoapps.user_api.preferences.api import set_user_preference, get_user_preference
+from openedx.core.djangoapps.user_api.preferences.api import set_user_preference, get_user_preference, delete_user_preference
 from student.tests.factories import UserFactory
 from student.tests.factories import AnonymousUserFactory
 
@@ -34,73 +38,117 @@ class TestUserPreferenceMiddleware(TestCase):
         self.request.META['HTTP_ACCEPT_LANGUAGE'] = 'ar;q=1.0'  # pylint: disable=no-member
         self.session_middleware.process_request(self.request)
 
-    def test_no_language_set_in_session_or_prefs(self):
-        # nothing set in the session or the prefs
-        self.middleware.process_request(self.request)
-        self.assertNotIn(LANGUAGE_SESSION_KEY, self.request.session)  # pylint: disable=no-member
-
-    @mock.patch(
-        'openedx.core.djangoapps.lang_pref.middleware.released_languages',
-        mock.Mock(return_value=[('eo', 'esperanto')])
-    )
-    def test_language_in_user_prefs(self):
-        # language set in the user preferences and not the session
-        set_user_preference(self.user, LANGUAGE_KEY, 'eo')
-        self.middleware.process_request(self.request)
-        self.assertEquals(self.request.session[LANGUAGE_SESSION_KEY], 'eo')  # pylint: disable=no-member
-
-    @mock.patch(
-        'openedx.core.djangoapps.lang_pref.middleware.released_languages',
-        mock.Mock(return_value=[('en', 'english'), ('eo', 'esperanto')])
-    )
-    def test_language_in_session(self):
-        # language set in both the user preferences and session,
-        # preference should get precedence. The session will hold the last value,
-        # which is probably the user's last preference. Look up the updated preference.
-
-        # Dark lang middleware should run after this middleware, so it can
-        # set a session language as an override of the user's preference.
-        self.request.session[LANGUAGE_SESSION_KEY] = 'en'  # pylint: disable=no-member
-        set_user_preference(self.user, LANGUAGE_KEY, 'eo')
-        self.middleware.process_request(self.request)
+    def test_logout_shouldnt_remove_cookie(self):
 
-        self.assertEquals(self.request.session[LANGUAGE_SESSION_KEY], 'eo')  # pylint: disable=no-member
+        self.middleware.process_request(self.request)
 
-    @mock.patch(
-        'openedx.core.djangoapps.lang_pref.middleware.released_languages',
-        mock.Mock(return_value=[('eo', 'dummy Esperanto'), ('ar', 'arabic'), ('eu-es', 'euskara (Espainia)')])
-    )
-    @ddt.data('ar;q=1.0', 'eu;q=1.0', 'es-419;q=1.0')
-    def test_browser_language_in_session_for_unauthenticated_user(self, accept_language):
-        """
-        test: browser language should not be set in user session for unauthenticated user.
-        """
-        self.request.META['HTTP_ACCEPT_LANGUAGE'] = accept_language  # pylint: disable=no-member
         self.request.user = self.anonymous_user
-        self.middleware.process_request(self.request)
-        self.assertNotIn(LANGUAGE_SESSION_KEY, self.request.session)   # pylint: disable=no-member
 
-    @mock.patch(
-        'openedx.core.djangoapps.lang_pref.middleware.released_languages',
-        mock.Mock(return_value=[('en', 'english')])
-    )
-    def test_browser_language_not_be_in_session(self):
+        response = mock.Mock(spec=HttpResponse)
+        self.middleware.process_response(self.request, response)
+
+        response.delete_cookie.assert_not_called()
+
+    @ddt.data(None, 'es', 'en')
+    def test_preference_setting_changes_cookie(self, lang_pref_out):
         """
-        test: browser language should not be set in user session if it is not supported by system.
+        Test that the LANGUAGE_COOKIE is always set to the user's current language preferences
+        at the end of the request, with an expiry that's the same as the users current session cookie.
         """
-        self.request.user = self.anonymous_user
+        if lang_pref_out:
+            set_user_preference(self.user, LANGUAGE_KEY, lang_pref_out)
+        else:
+            delete_user_preference(self.user, LANGUAGE_KEY)
+
+        response = mock.Mock(spec=HttpResponse)
+        self.middleware.process_response(self.request, response)
+
+        if lang_pref_out:
+            response.set_cookie.assert_called_with(
+                LANGUAGE_COOKIE,
+                value=lang_pref_out,
+                domain=settings.SESSION_COOKIE_DOMAIN,
+                max_age=COOKIE_DURATION,
+            )
+        else:
+            response.delete_cookie.assert_called_with(
+                LANGUAGE_COOKIE,
+                domain=settings.SESSION_COOKIE_DOMAIN,
+            )
+
+        self.assertNotIn(LANGUAGE_SESSION_KEY, self.request.session)
+
+    @ddt.data(*itertools.product(
+        (None, 'eo', 'es'),  # LANGUAGE_COOKIE
+        (None, 'es', 'en'),  # Language Preference In
+    ))
+    @ddt.unpack
+    @mock.patch('openedx.core.djangoapps.lang_pref.middleware.set_user_preference')
+    def test_preference_cookie_changes_setting(self, lang_cookie, lang_pref_in, mock_set_user_preference):
+        self.request.COOKIES[LANGUAGE_COOKIE] = lang_cookie
+
+        if lang_pref_in:
+            set_user_preference(self.user, LANGUAGE_KEY, lang_pref_in)
+        else:
+            delete_user_preference(self.user, LANGUAGE_KEY)
+
         self.middleware.process_request(self.request)
-        self.assertNotEqual(self.request.session.get(LANGUAGE_SESSION_KEY), 'ar')   # pylint: disable=no-member
 
-    @mock.patch(
-        'openedx.core.djangoapps.lang_pref.middleware.released_languages',
-        mock.Mock(return_value=[('en', 'english'), ('ar', 'arabic')])
-    )
-    def test_delete_user_lang_preference_not_supported_by_system(self):
-        """
-        test: user preferred language has been removed from user preferences model if it is not supported by system
-        for authenticated users.
-        """
-        set_user_preference(self.user, LANGUAGE_KEY, 'eo')
+        if lang_cookie is None:
+            self.assertEqual(mock_set_user_preference.mock_calls, [])
+        else:
+            mock_set_user_preference.assert_called_with(self.user, LANGUAGE_KEY, lang_cookie)
+
+    @ddt.data(*(
+        (logged_in, ) + test_def
+        for logged_in in (True, False)
+        for test_def in [
+            # (LANGUAGE_COOKIE, LANGUAGE_SESSION_KEY, Accept-Language In, Accept-Language Out)
+            (None, None, None, None),
+            (None, 'eo', None, None),
+            (None, 'eo', 'en', 'en'),
+            (None, None, 'en', 'en'),
+            ('en', None, None, 'en'),
+            ('en', None, 'eo', 'en;q=1.0,eo'),
+            ('en', None, 'en', 'en'),
+            ('en', 'eo', 'en', 'en'),
+            ('en', 'eo', 'eo', 'en;q=1.0,eo')
+        ]
+    ))
+    @ddt.unpack
+    def test_preference_cookie_overrides_browser(self, logged_in, lang_cookie, lang_session, accept_lang_in, accept_lang_out):
+        if not logged_in:
+            self.request.user = self.anonymous_user
+        if lang_cookie:
+            self.request.COOKIES[LANGUAGE_COOKIE] = lang_cookie
+        if lang_session:
+            self.request.session[LANGUAGE_SESSION_KEY] = lang_session
+        if accept_lang_in:
+            self.request.META['HTTP_ACCEPT_LANGUAGE'] = accept_lang_in
+        else:
+            del self.request.META['HTTP_ACCEPT_LANGUAGE']
+
         self.middleware.process_request(self.request)
-        self.assertEqual(get_user_preference(self.request.user, LANGUAGE_KEY), None)
+
+        accept_lang_result = self.request.META.get('HTTP_ACCEPT_LANGUAGE')
+        if accept_lang_result:
+            accept_lang_result = parse_accept_lang_header(accept_lang_result)
+
+        if accept_lang_out:
+            accept_lang_out = parse_accept_lang_header(accept_lang_out)
+
+        if accept_lang_out and accept_lang_result:
+            self.assertItemsEqual(accept_lang_result, accept_lang_out)
+        else:
+            self.assertEqual(accept_lang_result, accept_lang_out)
+
+        self.assertEquals(self.request.session.get(LANGUAGE_SESSION_KEY), lang_session)
+
+    def test_process_response_no_user_noop(self):
+        del self.request.user
+        response = mock.Mock(spec=HttpResponse)
+
+        result = self.middleware.process_response(self.request, response)
+
+        self.assertIs(result, response)
+        self.assertEqual(response.mock_calls, [])

openedx/core/djangoapps/lang_pref/views.py

@@ -9,7 +9,7 @@ from django.http import HttpResponse
 from django.views.decorators.csrf import ensure_csrf_cookie
 from django.utils.translation import LANGUAGE_SESSION_KEY
 
-from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY
+from openedx.core.djangoapps.lang_pref import LANGUAGE_KEY, LANGUAGE_COOKIE, COOKIE_DURATION
 
 
 @ensure_csrf_cookie
@@ -17,9 +17,16 @@ def update_session_language(request):
     """
     Update the language session key.
     """
+    response = HttpResponse(200)
     if request.method == 'PATCH':
         data = json.loads(request.body)
         language = data.get(LANGUAGE_KEY, settings.LANGUAGE_CODE)
         if request.session.get(LANGUAGE_SESSION_KEY, None) != language:
             request.session[LANGUAGE_SESSION_KEY] = unicode(language)
-    return HttpResponse(200)
+        response.set_cookie(
+            LANGUAGE_COOKIE,
+            language,
+            domain=settings.SESSION_COOKIE_DOMAIN,
+            max_age=COOKIE_DURATION
+        )
+    return response