Fixed #28284 -- Prevented Paginator's unordered object list warning from evaluating a QuerySet.

django/core/paginator.py

@@ -96,10 +96,16 @@ class Paginator:
         """
         Warn if self.object_list is unordered (typically a QuerySet).
         """
-        if hasattr(self.object_list, 'ordered') and not self.object_list.ordered:
+        ordered = getattr(self.object_list, 'ordered', None)
+        if ordered is not None and not ordered:
+            obj_list_repr = (
+                '{} {}'.format(self.object_list.model, self.object_list.__class__.__name__)
+                if hasattr(self.object_list, 'model')
+                else '{!r}'.format(self.object_list)
+            )
             warnings.warn(
                 'Pagination may yield inconsistent results with an unordered '
-                'object_list: {!r}'.format(self.object_list),
+                'object_list: {}.'.format(obj_list_repr),
                 UnorderedObjectListWarning,
                 stacklevel=3
             )

docs/releases/1.11.3.txt

@@ -32,3 +32,6 @@ Bugfixes
 
 * Fixed ``QuerySet.union()``, ``intersection()``, and ``difference()`` when
   combining with an ``EmptyQuerySet`` (:ticket:`28293`).
+
+* Prevented ``Paginator``’s unordered object list warning from evaluating a
+  ``QuerySet`` (:ticket:`28284`).

tests/pagination/tests.py

@@ -328,11 +328,25 @@ class ModelPaginationTests(TestCase):
         warning = warns[0]
         self.assertEqual(str(warning.message), (
             "Pagination may yield inconsistent results with an unordered "
-            "object_list: <QuerySet [<Article: Article 1>, "
+            "object_list: <class 'pagination.models.Article'> QuerySet."
-            "<Article: Article 2>, <Article: Article 3>, <Article: Article 4>, "
-            "<Article: Article 5>, <Article: Article 6>, <Article: Article 7>, "
-            "<Article: Article 8>, <Article: Article 9>]>"
         ))
         # The warning points at the Paginator caller (i.e. the stacklevel
         # is appropriate).
         self.assertEqual(warning.filename, __file__)
+
+    def test_paginating_unordered_object_list_raises_warning(self):
+        """
+        Unordered object list warning with an object that has an orderd
+        attribute but not a model attribute.
+        """
+        class ObjectList():
+            ordered = False
+        object_list = ObjectList()
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.filterwarnings('always', category=UnorderedObjectListWarning)
+            Paginator(object_list, 5)
+        self.assertEqual(len(warns), 1)
+        self.assertEqual(str(warns[0].message), (
+            "Pagination may yield inconsistent results with an unordered "
+            "object_list: {!r}.".format(object_list)
+        ))