bpo-43857: Improve the AttributeError message when deleting a missing attribute (#25424)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/Lib/test/test_class.py b/Lib/test/test_class.py
index 7cf5e06..91c53b7 100644
--- a/Lib/test/test_class.py
+++ b/Lib/test/test_class.py
@@ -611,6 +611,49 @@ class ClassTests(unittest.TestCase):
         with self.assertRaises(TypeError):
             type.__setattr__(A, b'x', None)
 
+    def testTypeAttributeAccessErrorMessages(self):
+        class A:
+            pass
+
+        error_msg = "type object 'A' has no attribute 'x'"
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            A.x
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            del A.x
+
+    def testObjectAttributeAccessErrorMessages(self):
+        class A:
+            pass
+        class B:
+            y = 0
+            __slots__ = ('z',)
+
+        error_msg = "'A' object has no attribute 'x'"
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            A().x
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            del A().x
+
+        error_msg = "'B' object has no attribute 'x'"
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            B().x
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            del B().x
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            B().x = 0
+
+        error_msg = "'B' object attribute 'y' is read-only"
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            del B().y
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            B().y = 0
+
+        error_msg = 'z'
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            B().z
+        with self.assertRaisesRegex(AttributeError, error_msg):
+            del B().z
+
     def testConstructorErrorMessages(self):
         # bpo-31506: Improves the error message logic for object_new & object_init