Merge pull request #23312 from edx/aehsan/prod-1222/fixed_pagination_for_course_api_view

Fixed pagination.

lms/djangoapps/course_api/tests/test_views.py

@@ -527,3 +527,24 @@ class LazyPageNumberPaginationTestCase(TestCase):
         paginated_queryset = pagination.paginate_queryset(even_numbers_lazy_sequence, request)
         paginated_response = pagination.get_paginated_response(paginated_queryset)
         self.assertDictEqual(expected_response, paginated_response.data)
+
+    def test_not_found_error_for_invalid_page(self):
+        number_sequence = range(20)
+        even_numbers_lazy_sequence = LazySequence(
+            (
+                number for number in number_sequence
+                if (number % 2) == 0
+            ),
+            est_len=len(number_sequence)
+        )
+
+        request = RequestFactory().get('/endpoint', data={'page': 3, 'page_size': 5})
+        request.query_params = {'page': 3, 'page_size': 5}
+
+        with self.assertRaises(Exception) as exc:
+            pagination = LazyPageNumberPagination()
+            pagination.max_page_size = 5
+            pagination.page_size = 5
+            paginated_queryset = pagination.paginate_queryset(even_numbers_lazy_sequence, request)
+            pagination.get_paginated_response(paginated_queryset)
+            self.assertIn('Invalid page', exc.exception)

lms/djangoapps/course_api/views.py

@@ -4,9 +4,11 @@ Course API Views
 
 
 from django.core.exceptions import ValidationError
+from django.core.paginator import InvalidPage
 from edx_rest_framework_extensions.paginators import NamespacedPageNumberPagination
 from rest_framework.generics import ListAPIView, RetrieveAPIView
 from rest_framework.throttling import UserRateThrottle
+from rest_framework.exceptions import NotFound
 
 from openedx.core.lib.api.view_utils import DeveloperErrorViewMixin, view_auth_classes
 
@@ -175,6 +177,20 @@ class LazyPageNumberPagination(NamespacedPageNumberPagination):
         del self.page.paginator.__dict__['count']
         del self.page.paginator.__dict__['num_pages']
 
+        # Paginate queryset function is using cached number of pages and sometime after
+        # deleting from cache when we recalculate number of pages are different and it raises
+        # EmptyPage error while accessing the previous page link. So we are catching that exception
+        # and raising 404. For more detail checkout PROD-1222
+        page_number = self.request.query_params.get(self.page_query_param, 1)
+        try:
+            self.page.paginator.validate_number(page_number)
+        except InvalidPage as exc:
+            msg = self.invalid_page_message.format(
+                page_number=page_number, message=str(exc)
+            )
+            self.page.number = self.page.paginator.num_pages
+            raise NotFound(msg)
+
         return super(LazyPageNumberPagination, self).get_paginated_response(data)