Fix cursor pagination ordering

requirements/requirements-testing.txt

@@ -6,3 +6,4 @@ importlib-metadata<5.0
 # temporary pin of attrs
 attrs==22.1.0
 pytz  # Remove when dropping support for Django<5.0
+setuptools>=77.0.3

rest_framework/pagination.py

@@ -11,6 +11,7 @@
 
 from django.core.paginator import InvalidPage
 from django.core.paginator import Paginator as DjangoPaginator
+from django.db.models import OrderBy
 from django.template import loader
 from django.utils.encoding import force_str
 from django.utils.translation import gettext_lazy as _
@@ -615,7 +616,7 @@ def paginate_queryset(self, queryset, request, view=None):
             return None
 
         self.base_url = request.build_absolute_uri()
-        self.ordering = self.get_ordering(request, queryset, view)
+        self.ordering = self.get_ordering(queryset)
 
         self.cursor = self.decode_cursor(request)
         if self.cursor is None:
@@ -624,10 +625,11 @@ def paginate_queryset(self, queryset, request, view=None):
             (offset, reverse, current_position) = self.cursor
 
         # Cursor pagination always enforces an ordering.
-        if reverse:
-            queryset = queryset.order_by(*_reverse_ordering(self.ordering))
-        else:
-            queryset = queryset.order_by(*self.ordering)
+        if not queryset.ordered:
+            if reverse:
+                queryset = queryset.order_by(*_reverse_ordering(self.ordering))
+            else:
+                queryset = queryset.order_by(*self.ordering)
 
         # If we have a cursor with a fixed position then filter by that.
         if current_position is not None:
@@ -801,27 +803,26 @@ def get_previous_link(self):
         cursor = Cursor(offset=offset, reverse=True, position=position)
         return self.encode_cursor(cursor)
 
-    def get_ordering(self, request, queryset, view):
+    def get_ordering(self, queryset):
         """
         Return a tuple of strings, that may be used in an `order_by` method.
         """
-        # The default case is to check for an `ordering` attribute
-        # on this pagination instance.
-        ordering = self.ordering
+        # Return the ordering value from the queryset if it has one.
+        if queryset.ordered:
+            ordering = []
 
-        ordering_filters = [
-            filter_cls for filter_cls in getattr(view, 'filter_backends', [])
-            if hasattr(filter_cls, 'get_ordering')
-        ]
+            for expr in queryset.query.order_by:
+                if isinstance(expr, str):
+                    ordering.append(expr)
+
+                elif isinstance(expr, OrderBy):
+                    field_name = expr.expression.name
+                    descending = expr.descending
+                    ordering.append(f"{'-' if descending else ''}{field_name}")
 
-        if ordering_filters:
-            # If a filter exists on the view that implements `get_ordering`
-            # then we defer to that filter to determine the ordering.
-            filter_cls = ordering_filters[0]
-            filter_instance = filter_cls()
-            ordering_from_filter = filter_instance.get_ordering(request, queryset, view)
-            if ordering_from_filter:
-                ordering = ordering_from_filter
+            return ordering
+
+        ordering = self.ordering
 
         assert ordering is not None, (
             'Using cursor pagination, but no ordering attribute was declared '

tests/test_pagination.py

@@ -616,42 +616,6 @@ def test_invalid_cursor(self):
         with pytest.raises(exceptions.NotFound):
             self.pagination.paginate_queryset(self.queryset, request)
 
-    def test_use_with_ordering_filter(self):
-        class MockView:
-            filter_backends = (filters.OrderingFilter,)
-            ordering_fields = ['username', 'created']
-            ordering = 'created'
-
-        request = Request(factory.get('/', {'ordering': 'username'}))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        assert ordering == ('username',)
-
-        request = Request(factory.get('/', {'ordering': '-username'}))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        assert ordering == ('-username',)
-
-        request = Request(factory.get('/', {'ordering': 'invalid'}))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        assert ordering == ('created',)
-
-    def test_use_with_ordering_filter_without_ordering_default_value(self):
-        class MockView:
-            filter_backends = (filters.OrderingFilter,)
-            ordering_fields = ['username', 'created']
-
-        request = Request(factory.get('/'))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        # it gets the value of `ordering` provided by CursorPagination
-        assert ordering == ('created',)
-
-        request = Request(factory.get('/', {'ordering': 'username'}))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        assert ordering == ('username',)
-
-        request = Request(factory.get('/', {'ordering': 'invalid'}))
-        ordering = self.pagination.get_ordering(request, [], MockView())
-        assert ordering == ('created',)
-
     def test_cursor_pagination(self):
         (previous, current, next, previous_url, next_url) = self.get_pages('/')
 
@@ -969,8 +933,9 @@ def __init__(self, idx):
                 self.created = idx
 
         class MockQuerySet:
-            def __init__(self, items):
+            def __init__(self, items, ordered=False):
                 self.items = items
+                self.ordered = ordered
 
             def filter(self, created__gt=None, created__lt=None):
                 if created__gt is not None:
@@ -987,7 +952,7 @@ def filter(self, created__gt=None, created__lt=None):
 
             def order_by(self, *ordering):
                 if ordering[0].startswith('-'):
-                    return MockQuerySet(list(reversed(self.items)))
+                    return MockQuerySet(list(reversed(self.items)), ordered=True)
                 return self
 
             def __getitem__(self, sliced):

tox.ini

@@ -23,7 +23,6 @@ deps =
         djangomain: https://github.com/django/django/archive/main.tar.gz
         -rrequirements/requirements-testing.txt
         -rrequirements/requirements-optionals.txt
-        setuptools
 
 [testenv:base]
 ; Ensure optional dependencies are not required