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PEP 702: Runtime warnings (#112)
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JelleZijlstra authored Feb 7, 2023
1 parent 1039bb2 commit e81cb82
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Showing 2 changed files with 160 additions and 4 deletions.
120 changes: 119 additions & 1 deletion src/test_typing_extensions.py
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
from typing_extensions import NamedTuple
from typing_extensions import override, deprecated
from _typed_dict_test_helper import Foo, FooGeneric
import warnings

# Flags used to mark tests that only apply after a specific
# version of the typing module.
Expand Down Expand Up @@ -203,7 +204,7 @@ def static_method_bad_order():


class DeprecatedTests(BaseTestCase):
def test_deprecated(self):
def test_dunder_deprecated(self):
@deprecated("A will go away soon")
class A:
pass
Expand All @@ -230,6 +231,123 @@ def h(x):
self.assertEqual(len(overloads), 2)
self.assertEqual(overloads[0].__deprecated__, "no more ints")

def test_class(self):
@deprecated("A will go away soon")
class A:
pass

with self.assertWarnsRegex(DeprecationWarning, "A will go away soon"):
A()
with self.assertRaises(TypeError):
A(42)

@deprecated("HasInit will go away soon")
class HasInit:
def __init__(self, x):
self.x = x

with self.assertWarnsRegex(DeprecationWarning, "HasInit will go away soon"):
instance = HasInit(42)
self.assertEqual(instance.x, 42)

has_new_called = False

@deprecated("HasNew will go away soon")
class HasNew:
def __new__(cls, x):
nonlocal has_new_called
has_new_called = True
return super().__new__(cls)

def __init__(self, x) -> None:
self.x = x

with self.assertWarnsRegex(DeprecationWarning, "HasNew will go away soon"):
instance = HasNew(42)
self.assertEqual(instance.x, 42)
self.assertTrue(has_new_called)
new_base_called = False

class NewBase:
def __new__(cls, x):
nonlocal new_base_called
new_base_called = True
return super().__new__(cls)

def __init__(self, x) -> None:
self.x = x

@deprecated("HasInheritedNew will go away soon")
class HasInheritedNew(NewBase):
pass

with self.assertWarnsRegex(DeprecationWarning, "HasInheritedNew will go away soon"):
instance = HasInheritedNew(42)
self.assertEqual(instance.x, 42)
self.assertTrue(new_base_called)

def test_function(self):
@deprecated("b will go away soon")
def b():
pass

with self.assertWarnsRegex(DeprecationWarning, "b will go away soon"):
b()

def test_method(self):
class Capybara:
@deprecated("x will go away soon")
def x(self):
pass

instance = Capybara()
with self.assertWarnsRegex(DeprecationWarning, "x will go away soon"):
instance.x()

def test_property(self):
class Capybara:
@property
@deprecated("x will go away soon")
def x(self):
pass

@property
def no_more_setting(self):
return 42

@no_more_setting.setter
@deprecated("no more setting")
def no_more_setting(self, value):
pass

instance = Capybara()
with self.assertWarnsRegex(DeprecationWarning, "x will go away soon"):
instance.x

with warnings.catch_warnings():
warnings.simplefilter("error")
self.assertEqual(instance.no_more_setting, 42)

with self.assertWarnsRegex(DeprecationWarning, "no more setting"):
instance.no_more_setting = 42

def test_category(self):
@deprecated("c will go away soon", category=RuntimeWarning)
def c():
pass

with self.assertWarnsRegex(RuntimeWarning, "c will go away soon"):
c()

def test_turn_off_warnings(self):
@deprecated("d will go away soon", category=None)
def d():
pass

with warnings.catch_warnings():
warnings.simplefilter("error")
d()


class AnyTests(BaseTestCase):
def test_can_subclass(self):
Expand Down
44 changes: 41 additions & 3 deletions src/typing_extensions.py
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
import sys
import types as _types
import typing
import warnings


__all__ = [
Expand Down Expand Up @@ -2135,7 +2136,12 @@ def method(self) -> None:
else:
_T = typing.TypeVar("_T")

def deprecated(__msg: str) -> typing.Callable[[_T], _T]:
def deprecated(
__msg: str,
*,
category: typing.Optional[typing.Type[Warning]] = DeprecationWarning,
stacklevel: int = 1,
) -> typing.Callable[[_T], _T]:
"""Indicate that a class, function or overload is deprecated.
Usage:
Expand Down Expand Up @@ -2167,8 +2173,40 @@ def g(x: str) -> int: ...
"""
def decorator(__arg: _T) -> _T:
__arg.__deprecated__ = __msg
return __arg
if category is None:
__arg.__deprecated__ = __msg
return __arg
elif isinstance(__arg, type):
original_new = __arg.__new__
has_init = __arg.__init__ is not object.__init__

@functools.wraps(original_new)
def __new__(cls, *args, **kwargs):
warnings.warn(__msg, category=category, stacklevel=stacklevel + 1)
# Mirrors a similar check in object.__new__.
if not has_init and (args or kwargs):
raise TypeError(f"{cls.__name__}() takes no arguments")
if original_new is not object.__new__:
return original_new(cls, *args, **kwargs)
else:
return original_new(cls)

__arg.__new__ = staticmethod(__new__)
__arg.__deprecated__ = __new__.__deprecated__ = __msg
return __arg
elif callable(__arg):
@functools.wraps(__arg)
def wrapper(*args, **kwargs):
warnings.warn(__msg, category=category, stacklevel=stacklevel + 1)
return __arg(*args, **kwargs)

__arg.__deprecated__ = wrapper.__deprecated__ = __msg
return wrapper
else:
raise TypeError(
"@deprecated decorator with non-None category must be applied to "
f"a class or callable, not {__arg!r}"
)

return decorator

Expand Down

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