This is copied from python/typing_extensions#105.

Waiting for the other reviewers to pipe in? This seems pretty straightforward.

The PEP hasn't been accepted yet!

Planning to hit the merge button the moment the PEP is accepted :)

PEP 702 has been accepted, but it's changed since this PR. I'll update the PR soon to put the decorator in warnings and sync the implementation from typing-extensions.

The purpose of that is supposed to be to allow third-party runtime tools to detect that the original object was decorated with @deprecated. Is that insufficient?

The issue is when using deprecated the way Zac-HD wrote (Annotated[T, warnings.deprecated("message")]), no object is being decorated here (in other words, deprecated("message") returns another function yet to be called with the decorated object)

Got it. What if we did something like this?

diff --git a/Lib/warnings.py b/Lib/warnings.py
index 36da0e75c6..fc8a10e71f 100644
--- a/Lib/warnings.py
+++ b/Lib/warnings.py
@@ -621,6 +621,7 @@ def wrapper(*args, **kwargs):
                 f"a class or callable, not {arg!r}"
             )

+    decorator.__origin__ = deprecated
     return decorator

Then third-party code could do checks like this:

from typing import get_origin
from warnings import decorated

if get_origin(obj) is deprecated:
    ...  # it was a wrapper function returned by `warnings.deprecated("message")`

Doesn't seem to be get_origin's primary use (maybe docs should be updated), but that would avoid completely refactoring the current implementation!

Doesn't seem to be get_origin's primary use

It's already sorta awkwardly overloaded in what it means tbh — the __origin__ attribute of ParamSpecArgs instances doesn't really have the same semantics as the __origin__ attribute of generic aliases :)

A class seems somewhat more elegant to me, but yeah, that would work.

I'm OK with making it a class. It's not what the object is meant for, but it's a reasonable extension.

Using __origin__ feels hacky and wouldn't provide an easy way to get the deprecation message out.

Thanks @AlexWaygood for the review! I pushed some changes.