`get_function_signature_hook` is not invoked on function decorators

Chạy mypy trên bản tái hiện foo.py với plugin trong plug.py, rồi so sánh các lần gọi get_function_hook và get_function_signature_hook cho foo.deco. Truy vết đường đi dispatch của plugin khi gọi decorator và thêm hoặc cập nhật coverage để signature hook được gọi cho foo.deco; hoàn tất khi callback mong đợi xuất hiện mà không làm hỏng hành vi hook hiện có.

Bug Report

It seems to me there is no way to intercept and change the signature of a decorator during the invocation.

I see that get_function_hook has been called for foo.deco (eventually allowing me to change the return type of the decorator) but get_function_signature_hook is missing

To Reproduce

very basic example:

foo.py

from collections.abc import Callable
def deco(fun: Callable[..., None]) -> None: ...
@deco
def fun() -> None: ...

plug.py

from mypy.plugin import *
from mypy.types import *
from collections.abc import Callable

class CustomPlugin(Plugin):
    def get_function_hook(self, fullname: str) -> Callable[[FunctionContext], Type] | None:
        print(f'get_function_hook - {fullname=}')
        return None

    def get_function_signature_hook(self, fullname: str) -> Callable[[FunctionSigContext], FunctionLike] | None:
        print(f'get_function_signature_hook - {fullname=}')
        return None

def plugin(_version: str, /) -> type[Plugin]:
    return CustomPlugin

If I run mypy with the plugin and capture the stdout I get (avoiding the duplicates):

get_function_hook - fullname='enum.auto'
get_function_hook - fullname='foo.deco'
get_function_hook - fullname='<list>'
get_function_hook - fullname='typing_extensions.disjoint_base'
get_function_hook - fullname='typing_extensions.final'
get_function_hook - fullname='typing.final'
get_function_hook - fullname='typing.runtime_checkable'
get_function_hook - fullname='typing.type_check_only'
get_function_hook - fullname='warnings.deprecated'
get_function_signature_hook - fullname='enum.auto'
get_function_signature_hook - fullname='warnings.deprecate

Expected Behavior

get_function_signature_hook is called also for foo.deco

Actual Behavior

it's missing

Your Environment

mypy 2.3.1 (compiled: yes)
Python 3.14.0