[Python-checkins] [3.6] bpo-31588: Validate return value of __prepare__() methods (GH-3790)
Nick Coghlan
webhook-mailer at python.org
Wed Sep 27 12:21:35 EDT 2017
https://github.com/python/cpython/commit/084f80b82c564c8a3cef26fc6e56da188a379be2
commit: 084f80b82c564c8a3cef26fc6e56da188a379be2
branch: 3.6
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: Nick Coghlan <ncoghlan at gmail.com>
date: 2017-09-28T02:21:33+10:00
summary:
[3.6] bpo-31588: Validate return value of __prepare__() methods (GH-3790)
Class execution requires that __prepare__() methods return
a proper execution namespace. Check for that immediately
after calling __prepare__(), rather than passing it through
to the code execution machinery and potentially triggering
SystemError (in debug builds) or a cryptic TypeError
(in release builds).
Patch by Oren Milman.
(cherry picked from commit 5837d0418f47933b2e3c139bdee8a79c248a943c)
files:
A Misc/NEWS.d/next/Core and Builtins/2017-09-26-13-03-16.bpo-31588.wT9Iy7.rst
M Lib/test/test_types.py
M Python/bltinmodule.c
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 382ca03e5ad..d79429faf11 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -846,6 +846,28 @@ def __prepare__(*args):
self.assertIs(ns, expected_ns)
self.assertEqual(len(kwds), 0)
+ def test_bad___prepare__(self):
+ # __prepare__() must return a mapping.
+ class BadMeta(type):
+ @classmethod
+ def __prepare__(*args):
+ return None
+ with self.assertRaisesRegex(TypeError,
+ r'^BadMeta\.__prepare__\(\) must '
+ r'return a mapping, not NoneType$'):
+ class Foo(metaclass=BadMeta):
+ pass
+ # Also test the case in which the metaclass is not a type.
+ class BadMeta:
+ @classmethod
+ def __prepare__(*args):
+ return None
+ with self.assertRaisesRegex(TypeError,
+ r'^<metaclass>\.__prepare__\(\) must '
+ r'return a mapping, not NoneType$'):
+ class Bar(metaclass=BadMeta()):
+ pass
+
def test_metaclass_derivation(self):
# issue1294232: correct metaclass calculation
new_calls = [] # to check the order of __new__ calls
diff --git a/Misc/NEWS.d/next/Core and Builtins/2017-09-26-13-03-16.bpo-31588.wT9Iy7.rst b/Misc/NEWS.d/next/Core and Builtins/2017-09-26-13-03-16.bpo-31588.wT9Iy7.rst
new file mode 100644
index 00000000000..44a7aba9d7f
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2017-09-26-13-03-16.bpo-31588.wT9Iy7.rst
@@ -0,0 +1,2 @@
+Raise a `TypeError` with a helpful error message when class creation fails
+due to a metaclass with a bad ``__prepare__()`` method. Patch by Oren Milman.
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 911e2ba79ef..1960a095b8d 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -167,6 +167,13 @@ builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
Py_DECREF(bases);
return NULL;
}
+ if (!PyMapping_Check(ns)) {
+ PyErr_Format(PyExc_TypeError,
+ "%.200s.__prepare__() must return a mapping, not %.200s",
+ isclass ? ((PyTypeObject *)meta)->tp_name : "<metaclass>",
+ Py_TYPE(ns)->tp_name);
+ goto error;
+ }
cell = PyEval_EvalCodeEx(PyFunction_GET_CODE(func), PyFunction_GET_GLOBALS(func), ns,
NULL, 0, NULL, 0, NULL, 0, NULL,
PyFunction_GET_CLOSURE(func));
More information about the Python-checkins
mailing list