use context processor instead of middleware

lms/djangoapps/shoppingcart/middleware.py → lms/djangoapps/shoppingcart/context_processor.py

 """
-This is the shoppingcart middleware class.
-Currently the only middleware is detects whether request.user has a cart that should be displayed in the
-navigation.  We want to do this in the middleware to
+This is the shoppingcart context_processor module.
+Currently the only context_processor detects whether request.user has a cart that should be displayed in the
+navigation.  We want to do this in the context_processor to
 1) keep database accesses out of templates (this led to a transaction bug with user email changes)
 2) because navigation.html is "called" by being included in other templates, there's no "views.py" to put this.
 """
@@ -9,26 +9,18 @@ from django.conf import settings
 import shoppingcart
 
 
-class UserHasCartMiddleware(object):
+def user_has_cart_context_processor(request):
     """
-    Detects whether request.user has a cart and sets it as part of the request
-
-    ***
-     Because this relies on request.user, it needs to enabled in settings after
-     django.contrib.auth.middleware.AuthenticationMiddleware (or equivalent)
-    ***
+    Checks if request has an authenticated user.  If so, checks if request.user has a cart that should
+    be displayed.  Anonymous users don't.
+    Adds `display_shopping_cart` to the context
     """
-    def process_request(self, request):
-        """
-        Checks if request has an authenticated user.  If so, checks if request.user has a cart that should
-        be displayed.  Anonymous users don't.
-        """
-        request.display_shopping_cart = False
-        if (
-            request.user.is_authenticated() and                                # user exists
-            settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION') and  # settings is set
-            settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART') and             # setting is set
-            shoppingcart.models.Order.user_cart_has_items(request.user)        # user's cart is non-empty
-        ):
-            request.display_shopping_cart = True
-        return None
+    display_shopping_cart = False
+    if (
+        request.user.is_authenticated() and                                # user exists
+        settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION') and  # settings is set
+        settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART') and             # setting is set
+        shoppingcart.models.Order.user_cart_has_items(request.user)        # user's cart is non-empty
+    ):
+        display_shopping_cart = True
+    return {'display_shopping_cart': display_shopping_cart}

lms/djangoapps/shoppingcart/tests/test_middleware.py → lms/djangoapps/shoppingcart/tests/test_context_processor.py

 """
-Unit tests for shoppingcart middleware
+Unit tests for shoppingcart context_processor
 """
 from mock import patch, Mock
 from django.conf import settings
@@ -10,31 +10,26 @@ from courseware.tests.tests import TEST_DATA_MONGO_MODULESTORE
 from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
 from xmodule.modulestore.tests.factories import CourseFactory
 from student.tests.factories import UserFactory
-from course_modes.models import CourseMode
+from course_modes.tests.factories import CourseModeFactory
 from shoppingcart.models import Order, PaidCourseRegistration
-from shoppingcart.middleware import UserHasCartMiddleware
+from shoppingcart.context_processor import user_has_cart_context_processor
 
 
 @override_settings(MODULESTORE=TEST_DATA_MONGO_MODULESTORE)
-class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
+class UserCartContextProcessorUnitTest(ModuleStoreTestCase):
     """
-    Unit test for shoppingcart middleware UserHasCartMiddleware
+    Unit test for shoppingcart context_processor
     """
     def setUp(self):
         self.user = UserFactory.create()
         self.request = Mock()
-        self.middleware = UserHasCartMiddleware()
 
     def add_to_cart(self):
         """
         Adds content to self.user's cart
         """
         course = CourseFactory.create(org='MITx', number='999', display_name='Robot Super Course')
-        course_mode = CourseMode(course_id=course.id,
-                                 mode_slug="honor",
-                                 mode_display_name="honor cert",
-                                 min_price=40)
-        course_mode.save()
+        CourseModeFactory(course_id=course.id)
         cart = Order.get_cart_for_user(self.user)
         PaidCourseRegistration.add_to_order(cart, course.id)
 
@@ -45,8 +40,8 @@ class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
         """
         self.add_to_cart()
         self.request.user = self.user
-        self.middleware.process_request(self.request)
-        self.assertFalse(self.request.display_shopping_cart)
+        context = user_has_cart_context_processor(self.request)
+        self.assertFalse(context['display_shopping_cart'])
 
     @patch.dict(settings.MITX_FEATURES, {'ENABLE_SHOPPING_CART': True, 'ENABLE_PAID_COURSE_REGISTRATION': False})
     def test_no_enable_paid_course_registration(self):
@@ -55,8 +50,8 @@ class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
         """
         self.add_to_cart()
         self.request.user = self.user
-        self.middleware.process_request(self.request)
-        self.assertFalse(self.request.display_shopping_cart)
+        context = user_has_cart_context_processor(self.request)
+        self.assertFalse(context['display_shopping_cart'])
 
     @patch.dict(settings.MITX_FEATURES, {'ENABLE_SHOPPING_CART': True, 'ENABLE_PAID_COURSE_REGISTRATION': True})
     def test_anonymous_user(self):
@@ -64,8 +59,8 @@ class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
         Tests when request.user is anonymous
         """
         self.request.user = AnonymousUser()
-        self.middleware.process_request(self.request)
-        self.assertFalse(self.request.display_shopping_cart)
+        context = user_has_cart_context_processor(self.request)
+        self.assertFalse(context['display_shopping_cart'])
 
     @patch.dict(settings.MITX_FEATURES, {'ENABLE_SHOPPING_CART': True, 'ENABLE_PAID_COURSE_REGISTRATION': True})
     def test_no_items_in_cart(self):
@@ -73,8 +68,8 @@ class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
         Tests when request.user doesn't have a cart with items
         """
         self.request.user = self.user
-        self.middleware.process_request(self.request)
-        self.assertFalse(self.request.display_shopping_cart)
+        context = user_has_cart_context_processor(self.request)
+        self.assertFalse(context['display_shopping_cart'])
 
     @patch.dict(settings.MITX_FEATURES, {'ENABLE_SHOPPING_CART': True, 'ENABLE_PAID_COURSE_REGISTRATION': True})
     def test_items_in_cart(self):
@@ -83,5 +78,5 @@ class UserCartMiddlewareUnitTest(ModuleStoreTestCase):
         """
         self.add_to_cart()
         self.request.user = self.user
-        self.middleware.process_request(self.request)
-        self.assertTrue(self.request.display_shopping_cart)
+        context = user_has_cart_context_processor(self.request)
+        self.assertTrue(context['display_shopping_cart'])

lms/envs/common.py

@@ -272,6 +272,9 @@ TEMPLATE_CONTEXT_PROCESSORS = (
 
     # Hack to get required link URLs to password reset templates
     'mitxmako.shortcuts.marketing_link_context_processor',
+
+    # Shoppingcart processor (detects if request.user has a cart)
+    'shoppingcart.context_processor.user_has_cart_context_processor',
 )
 
 # use the ratelimit backend to prevent brute force attacks
@@ -610,9 +613,6 @@ MIDDLEWARE_CLASSES = (
 
     # For A/B testing
     'waffle.middleware.WaffleMiddleware',
-
-    # Shoppingcart middleware (detects if request.user has a cart)
-    'shoppingcart.middleware.UserHasCartMiddleware',
 )
 
 ############################### Pipeline #######################################

lms/templates/navigation.html

@@ -81,7 +81,7 @@ site_status_msg = get_site_status_msg(course_id)
         </ul>
       </li>
     </ol>
-      % if getattr(request, 'display_shopping_cart', False): # see shoppingcart.middleware.UserHasCartMiddleware
+      % if display_shopping_cart: # see shoppingcart.context_processor.user_has_cart_context_processor
         <ol class="user">
           <li class="primary">
             <a class="shopping-cart" href="${reverse('shoppingcart.views.show_cart')}">