gh-104614: Make Sure ob_type is Always Set Correctly by PyType_Ready() (gh-105122)

When I added the relevant condition to type_ready_set_bases() in gh-103912, I had missed that the function also sets tp_base and ob_type (if necessary).  That led to problems for third-party static types.

We fix that here, by making those extra operations distinct and by adjusting the condition to be more specific.

1 files changed, 37 insertions, 1 deletions

diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
index 037c811..e1b55cf 100644
--- a/Lib/test/test_capi/test_misc.py
+++ b/Lib/test/test_capi/test_misc.py
@@ -1,8 +1,9 @@
 # Run the _testcapi module tests (tests for the Python/C API):  by defn,
 # these are all functions _testcapi exports whose name begins with 'test_'.
 
-from collections import OrderedDict
 import _thread
+from collections import OrderedDict
+import contextlib
 import importlib.machinery
 import importlib.util
 import os
@@ -1626,6 +1627,41 @@ class BuiltinStaticTypesTests(unittest.TestCase):
                 self.assertIsNot(mro, None)
 
 
+class TestStaticTypes(unittest.TestCase):
+
+    _has_run = False
+
+    @classmethod
+    def setUpClass(cls):
+        # The tests here don't play nice with our approach to refleak
+        # detection, so we bail out in that case.
+        if cls._has_run:
+            raise unittest.SkipTest('these tests do not support re-running')
+        cls._has_run = True
+
+    @contextlib.contextmanager
+    def basic_static_type(self, *args):
+        cls = _testcapi.get_basic_static_type(*args)
+        yield cls
+
+    def test_pytype_ready_always_sets_tp_type(self):
+        # The point of this test is to prevent something like
+        # https://github.com/python/cpython/issues/104614
+        # from happening again.
+
+        # First check when tp_base/tp_bases is *not* set before PyType_Ready().
+        with self.basic_static_type() as cls:
+            self.assertIs(cls.__base__, object);
+            self.assertEqual(cls.__bases__, (object,));
+            self.assertIs(type(cls), type(object));
+
+        # Then check when we *do* set tp_base/tp_bases first.
+        with self.basic_static_type(object) as cls:
+            self.assertIs(cls.__base__, object);
+            self.assertEqual(cls.__bases__, (object,));
+            self.assertIs(type(cls), type(object));
+
+
 class TestThreadState(unittest.TestCase):
 
     @threading_helper.reap_threads