Replacing Callable[[T], T] with callback protocol in click (#4045)

third_party/2and3/click/decorators.pyi

@@ -1,13 +1,14 @@
 from distutils.version import Version
-from typing import Any, Callable, Dict, List, Optional, Tuple, Type, TypeVar, Union, Text, overload
+from typing import Any, Callable, Dict, List, Optional, Tuple, Type, TypeVar, Union, Text, overload, Protocol
 
 from click.core import Command, Group, Argument, Option, Parameter, Context, _ConvertibleType
 
 _T = TypeVar('_T')
 _F = TypeVar('_F', bound=Callable[..., Any])
 
-# Until https://github.com/python/mypy/issues/3924 is fixed you can't do the following:
-# _Decorator = Callable[[_F], _F]
+class _IdentityFunction(Protocol):
+    def __call__(self, __x: _T) -> _T: ...
+
 
 _Callback = Callable[
     [Context, Union[Option, Parameter], Any],
@@ -24,7 +25,7 @@ def pass_obj(__f: _T) -> _T:
 
 def make_pass_decorator(
     object_type: type, ensure: bool = ...
-) -> Callable[[_T], _T]:
+) -> _IdentityFunction:
     ...
 
 
@@ -85,7 +86,7 @@ def argument(
     is_eager: bool = ...,
     envvar: Optional[Union[str, List[str]]] = ...,
     autocompletion: Optional[Callable[[Any, List[str], str], List[Union[str, Tuple[str, str]]]]] = ...,
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -117,7 +118,7 @@ def option(
     envvar: Optional[Union[str, List[str]]] = ...,
     # User-defined
     **kwargs: Any,
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -149,7 +150,7 @@ def option(
     envvar: Optional[Union[str, List[str]]] = ...,
     # User-defined
     **kwargs: Any,
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -181,7 +182,7 @@ def option(
     envvar: Optional[Union[str, List[str]]] = ...,
     # User-defined
     **kwargs: Any,
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -213,7 +214,7 @@ def option(
     envvar: Optional[Union[str, List[str]]] = ...,
     # User-defined
     **kwargs: Any,
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -241,7 +242,7 @@ def confirmation_option(
     expose_value: bool = ...,
     is_eager: bool = ...,
     envvar: Optional[Union[str, List[str]]] = ...
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -269,7 +270,7 @@ def password_option(
     expose_value: bool = ...,
     is_eager: bool = ...,
     envvar: Optional[Union[str, List[str]]] = ...
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -300,7 +301,7 @@ def version_option(
     expose_value: bool = ...,
     is_eager: bool = ...,
     envvar: Optional[Union[str, List[str]]] = ...
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...
 
 
@@ -328,5 +329,5 @@ def help_option(
     expose_value: bool = ...,
     is_eager: bool = ...,
     envvar: Optional[Union[str, List[str]]] = ...
-) -> Callable[[_F], _F]:
+) -> _IdentityFunction:
     ...