Fixed #29244 -- Prevented Paginator.count() from silencing TypeError and AttributeError.

django/core/paginator.py

@@ -1,8 +1,10 @@
 import collections.abc
+import inspect
 import warnings
 from math import ceil
 
 from django.utils.functional import cached_property
+from django.utils.inspect import method_has_no_args
 from django.utils.translation import gettext_lazy as _
 
 
@@ -83,13 +85,10 @@ class Paginator:
     @cached_property
     def count(self):
         """Return the total number of objects, across all pages."""
-        try:
-            return self.object_list.count()
-        except (AttributeError, TypeError):
-            # AttributeError if object_list has no count() method.
-            # TypeError if object_list.count() requires arguments
-            # (i.e. is of type list).
-            return len(self.object_list)
+        c = getattr(self.object_list, 'count', None)
+        if callable(c) and not inspect.isbuiltin(c) and method_has_no_args(c):
+            return c()
+        return len(self.object_list)
 
     @cached_property
     def num_pages(self):

tests/pagination/tests.py

@@ -1,4 +1,3 @@
-import unittest
 import warnings
 from datetime import datetime
 
@@ -6,13 +5,13 @@ from django.core.paginator import (
     EmptyPage, InvalidPage, PageNotAnInteger, Paginator,
     UnorderedObjectListWarning,
 )
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 
 from .custom import ValidAdjacentNumsPaginator
 from .models import Article
 
 
-class PaginationTests(unittest.TestCase):
+class PaginationTests(SimpleTestCase):
     """
     Tests for the Paginator and Page classes.
     """
@@ -151,6 +150,22 @@ class PaginationTests(unittest.TestCase):
         self.assertEqual(5, paginator.num_pages)
         self.assertEqual([1, 2, 3, 4, 5], list(paginator.page_range))
 
+    def test_count_does_not_silence_attribute_error(self):
+        class AttributeErrorContainer:
+            def count(self):
+                raise AttributeError('abc')
+
+        with self.assertRaisesMessage(AttributeError, 'abc'):
+            Paginator(AttributeErrorContainer(), 10).count()
+
+    def test_count_does_not_silence_type_error(self):
+        class TypeErrorContainer:
+            def count(self):
+                raise TypeError('abc')
+
+        with self.assertRaisesMessage(TypeError, 'abc'):
+            Paginator(TypeErrorContainer(), 10).count()
+
     def check_indexes(self, params, page_num, indexes):
         """
         Helper method that instantiates a Paginator object from the passed