gh-132493: Avoid eager import of annotationlib in typing (again)

Lib/test/test_typing.py

@@ -3149,6 +3149,21 @@ def x(self): ...
  with self.assertRaisesRegex(TypeError, only_classes_allowed):
  issubclass(1, BadPG)
 
+ def test_isinstance_against_superproto_doesnt_affect_subproto_instance(self):
+ @runtime_checkable
+ class Base(Protocol):
+ x: int
+
+ @runtime_checkable
+ class Child(Base, Protocol):
+ y: str
+
+ class Capybara:
+ x = 43
+
+ self.assertIsInstance(Capybara(), Base)
+ self.assertNotIsInstance(Capybara(), Child)
+
  def test_implicit_issubclass_between_two_protocols(self):
  @runtime_checkable
  class CallableMembersProto(Protocol):
@@ -6323,7 +6338,7 @@ def test_lazy_import(self):
  "inspect",
  "re",
  "contextlib",
-# "annotationlib", # TODO
+ "annotationlib",
  })
 
 

Lib/typing.py

@@ -1801,9 +1801,13 @@ def _get_protocol_attrs(cls):
  for base in cls.__mro__[:-1]: # without object
  if base.__name__ in{'Protocol', 'Generic'}:
  continue
- annotations = _lazy_annotationlib.get_annotations(
- base, format=_lazy_annotationlib.Format.FORWARDREF
- )
+ try:
+ annotations = base.__annotations__
+ except Exception:
+ # Only go through annotationlib to handle deferred annotations if we need to
+ annotations = _lazy_annotationlib.get_annotations(
+ base, format=_lazy_annotationlib.Format.FORWARDREF
+ )
  for attr in (*base.__dict__, *annotations):
  if not attr.startswith('_abc_') and attr not in EXCLUDED_ATTRIBUTES:
  attrs.add(attr)
@@ -2020,14 +2024,17 @@ def _proto_hook(cls, other):
  break
 
  # ...or in annotations, if it is a sub-protocol.
- if (
- issubclass(other, Generic)
- and getattr(other, "_is_protocol", False)
- and attr in _lazy_annotationlib.get_annotations(
- base, format=_lazy_annotationlib.Format.FORWARDREF
- )
- ):
- break
+ if issubclass(other, Generic) and getattr(other, "_is_protocol", False):
+ # We avoid the slower path through annotationlib here because in most
+ # cases it should be unnecessary.
+ try:
+ annos = base.__annotations__
+ except Exception:
+ annos = _lazy_annotationlib.get_annotations(
+ base, format=_lazy_annotationlib.Format.FORWARDREF
+ )
+ if attr in annos:
+ break
  else:
  return NotImplemented
  return True