bpo-38908: Fix issue when non runtime_protocol failed to raise TypeError (#26067)
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 47dc0b9..a2a5d8f 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -1422,6 +1422,14 @@
class CustomContextManager(typing.ContextManager, Protocol):
pass
+ def test_non_runtime_protocol_isinstance_check(self):
+ class P(Protocol):
+ x: int
+
+ with self.assertRaisesRegex(TypeError, "@runtime_checkable"):
+ isinstance(1, P)
+
+
class GenericTests(BaseTestCase):
def test_basics(self):
diff --git a/Lib/typing.py b/Lib/typing.py
index a51452b..ca47a6f 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1343,14 +1343,14 @@
raise TypeError('Protocols cannot be instantiated')
-def _allow_reckless_class_checks():
+def _allow_reckless_class_checks(depth=3):
"""Allow instance and class checks for special stdlib modules.
The abc and functools modules indiscriminately call isinstance() and
issubclass() on the whole MRO of a user class, which may contain protocols.
"""
try:
- return sys._getframe(3).f_globals['__name__'] in ['abc', 'functools']
+ return sys._getframe(depth).f_globals['__name__'] in ['abc', 'functools']
except (AttributeError, ValueError): # For platforms without _getframe().
return True
@@ -1370,6 +1370,14 @@
def __instancecheck__(cls, instance):
# We need this method for situations where attributes are
# assigned in __init__.
+ if (
+ getattr(cls, '_is_protocol', False) and
+ not getattr(cls, '_is_runtime_protocol', False) and
+ not _allow_reckless_class_checks(depth=2)
+ ):
+ raise TypeError("Instance and class checks can only be used with"
+ " @runtime_checkable protocols")
+
if ((not getattr(cls, '_is_protocol', False) or
_is_callable_members_only(cls)) and
issubclass(instance.__class__, cls)):
diff --git a/Misc/NEWS.d/next/Library/2021-05-12-16-43-21.bpo-38908.nM2_rO.rst b/Misc/NEWS.d/next/Library/2021-05-12-16-43-21.bpo-38908.nM2_rO.rst
new file mode 100644
index 0000000..b72936c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-05-12-16-43-21.bpo-38908.nM2_rO.rst
@@ -0,0 +1,5 @@
+Fix issue where :mod:`typing` protocols without the ``@runtime_checkable``
+decorator did not raise a ``TypeError`` when used with ``issubclass`` and
+``isinstance``. Now, subclassses of ``typing.Protocol`` will raise a
+``TypeError`` when used with with those checks.
+Patch provided by Yurii Karabas.