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Improve abc module and builtin function decorators (with ParamSpec) #5682

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f03d008
Improve abc module and builtin function decorators
srittau Jun 23, 2021
f40490b
Remove unused imports
srittau Jun 23, 2021
16b9d8a
Add constructors to abstract{class,static}method
srittau Jun 23, 2021
409aaa1
Use ParamSpec for classmethod
srittau Jun 28, 2021
df2f05f
Merge branch 'master' into abcmeta
srittau Jun 28, 2021
02ab1b6
Fixes
srittau Jun 28, 2021
704dc43
Fix ParamSpec
srittau Jun 28, 2021
8d73ca4
Fix abstractclassmethod
srittau Jun 28, 2021
e0f6ee1
Fix typo
srittau Jun 28, 2021
ddfd634
Consistent type var names
srittau Jun 28, 2021
06a0ce0
@{static,class}method takes pos-only arguments
srittau Jun 28, 2021
aa5c5df
Annotate self
srittau Jun 28, 2021
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17 changes: 9 additions & 8 deletions stdlib/abc.pyi
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Original file line number Diff line number Diff line change
@@ -1,19 +1,20 @@
from typing import Any, Callable, Type, TypeVar
from typing import Any, Callable, Generic, Type, TypeVar

_T = TypeVar("_T")
_FuncT = TypeVar("_FuncT", bound=Callable[..., Any])

# These definitions have special processing in mypy
class ABCMeta(type):
def register(cls: ABCMeta, subclass: Type[_T]) -> Type[_T]: ...

def abstractmethod(funcobj: _FuncT) -> _FuncT: ...

class abstractclassmethod(classmethod[_FuncT], Generic[_FuncT]):
def __init__(self, callable: _FuncT) -> None: ...

class abstractstaticmethod(staticmethod[_FuncT], Generic[_FuncT]):
def __init__(self, callable: _FuncT) -> None: ...

class abstractproperty(property): ...

# These two are deprecated and not supported by mypy
def abstractstaticmethod(callable: _FuncT) -> _FuncT: ...
def abstractclassmethod(callable: _FuncT) -> _FuncT: ...
class ABCMeta(type):
def register(cls: ABCMeta, subclass: Type[_T]) -> Type[_T]: ...

class ABC(metaclass=ABCMeta): ...

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19 changes: 10 additions & 9 deletions stdlib/builtins.pyi
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Expand Up @@ -16,6 +16,7 @@ from _typeshed import (
SupportsWrite,
)
from ast import AST, mod
from collections.abc import Callable
from io import BufferedRandom, BufferedReader, BufferedWriter, FileIO, TextIOWrapper
from types import CodeType, TracebackType
from typing import (
Expand All @@ -26,7 +27,6 @@ from typing import (
AsyncIterator,
BinaryIO,
ByteString,
Callable,
Dict,
FrozenSet,
Generic,
Expand Down Expand Up @@ -80,6 +80,7 @@ _T4 = TypeVar("_T4")
_T5 = TypeVar("_T5")
_TT = TypeVar("_TT", bound="type")
_TBE = TypeVar("_TBE", bound="BaseException")
_FuncT = TypeVar("_FuncT", bound=Callable[..., Any])

class object:
__doc__: Optional[str]
Expand Down Expand Up @@ -109,19 +110,19 @@ class object:
def __dir__(self) -> Iterable[str]: ...
def __init_subclass__(cls) -> None: ...

class staticmethod(object): # Special, only valid as a decorator.
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Nit: These comments should be deleted. They seem misleading and mypy-specific to me.

__func__: Callable[..., Any]
class staticmethod(Generic[_FuncT]): # Special, only valid as a decorator.
__func__: _FuncT
__isabstractmethod__: bool
def __init__(self, f: Callable[..., Any]) -> None: ...
def __init__(self, f: _FuncT) -> None: ...
def __new__(cls: Type[_T], *args: Any, **kwargs: Any) -> _T: ...
def __get__(self, obj: _T, type: Optional[Type[_T]] = ...) -> Callable[..., Any]: ...
def __get__(self, obj: _T, type: Type[_T] | None = ...) -> _FuncT: ...

class classmethod(object): # Special, only valid as a decorator.
__func__: Callable[..., Any]
class classmethod(Generic[_FuncT]): # Special, only valid as a decorator.
__func__: _FuncT
__isabstractmethod__: bool
def __init__(self, f: Callable[..., Any]) -> None: ...
def __init__(self, f: _FuncT) -> None: ...
def __new__(cls: Type[_T], *args: Any, **kwargs: Any) -> _T: ...
def __get__(self, obj: _T, type: Optional[Type[_T]] = ...) -> Callable[..., Any]: ...
def __get__(self, obj: _T, type: Type[_T] | None = ...) -> _FuncT: ...
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This doesn't seem right, because the callable returned from __get__ doesn't take the class as a first argument.

>>> class Foo:
...     @classmethod
...     def bar(cls):
...             print("Bar runs:", cls)
... 
>>> Foo.bar()
Bar runs: <class '__main__.Foo'>
>>> Foo.__dict__['bar'].__func__(Foo)
Bar runs: <class '__main__.Foo'>

Here Foo.__dict__['bar'] is the classmethod object, and for Foo.bar, its __get__ method gets called. The result is a bound method, which basically means that it includes the class similarly to partial:

>>> Foo.bar == Foo.__dict__['bar'].__get__(Foo(), None)
True
>>> Foo.bar
<bound method Foo.bar of <class '__main__.Foo'>>

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Another problem: I think it calls __get__(None, Foo) when looking up Foo.bar, so None should be allowed for the first argument to __get__.

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Good catch. I tried to express this using ParamSpec, but I'm not sure this is correct. Also, do you know in what circumstances the owner argument can be None or not set?

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@Akuli Akuli Jun 28, 2021 •
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It appears to be a technicality that doesn't really occur in practice: "Python’s own __getattribute__() implementation always passes in both arguments whether they are required or not." Docs


class type(object):
__base__: type
Expand Down