Autospeccing with `unittest.mock` is less robust with PEP 649

[Daverball]

Bug report

Bug description:

from typing import TYPE_CHECKING
from unittest.mock import create_autospec

if TYPE_CHECKING:
    from foo import Foo

def bar(x: Foo) -> None:
    pass

create_autospec(bar)

This will result in NameError: name 'Foo' is not defined because _get_signature_object in unittest.mock calls inspect.signature without explicitly passing annotation_format, so it defaults to Format.VALUE.

Since create_autospec really shouldn't care whether or not the annotations can be evaluated at runtime on the given object, I would suggest switching over to Format.FORWARDREF or Format.STRING, so autospeccing continues to work in Python 3.14+ for people that used to rely on from __future__ import annotations and now want to switch to PEP 649 semantics, without needing to change their code.

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs

• gh-145754: Update signature retrieval in unittest.mock to use forwardref annotation format #145756