bpo-38008: Move builtin protocol whitelist to mapping instead of list (GH-15647)

Fixes https://bugs.python.org/issue38008

1 files changed, 9 insertions, 5 deletions

diff --git a/Lib/typing.py b/Lib/typing.py
index 5f1a0ad3d6..7b07112c3a 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -989,10 +989,13 @@ def _allow_reckless_class_cheks():
         return True
 
 
-_PROTO_WHITELIST = ['Callable', 'Awaitable',
-                    'Iterable', 'Iterator', 'AsyncIterable', 'AsyncIterator',
-                    'Hashable', 'Sized', 'Container', 'Collection', 'Reversible',
-                    'ContextManager', 'AsyncContextManager']
+_PROTO_WHITELIST = {
+    'collections.abc': [
+        'Callable', 'Awaitable', 'Iterable', 'Iterator', 'AsyncIterable',
+        'Hashable', 'Sized', 'Container', 'Collection', 'Reversible',
+    ],
+    'contextlib': ['AbstractContextManager', 'AbstractAsyncContextManager'],
+}
 
 
 class _ProtocolMeta(ABCMeta):
@@ -1105,7 +1108,8 @@ class Protocol(Generic, metaclass=_ProtocolMeta):
         # ... otherwise check consistency of bases, and prohibit instantiation.
         for base in cls.__bases__:
             if not (base in (object, Generic) or
-                    base.__module__ == 'collections.abc' and base.__name__ in _PROTO_WHITELIST or
+                    base.__module__ in _PROTO_WHITELIST and
+                    base.__name__ in _PROTO_WHITELIST[base.__module__] or
                     issubclass(base, Generic) and base._is_protocol):
                 raise TypeError('Protocols can only inherit from other'
                                 ' protocols, got %r' % base)