#36696: django.utils.inspect leads to NameError with Python 3.14
-------------------------------------+-------------------------------------
Reporter: Patrick Rauscher | Owner: (none)
Type: Bug | Status: new
Component: Utilities | Version: 5.2
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
typing,inspect,deferred |
annotations |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Jacob Walls):
* keywords: typing,inspect => typing,inspect,deferred annotations
* severity: Normal => Release blocker
* stage: Unreviewed => Accepted
* type: Uncategorized => Bug
Old description:
> Starting with Python 3.14, deferred evaluation of annotations (PEP-649)
> is default now. This would suggest that using annotations in templatetags
> or signals should be as easy as:
>
> {{{
> from typing import TYPE_CHECKING
> from django.contrib.auth.signals import user_logged_in
> from django.dispatch import receiver
>
> if TYPE_CHECKING:
> from django.http import HttpRequest
>
> @receiver(user_logged_in)
> def handle_successful_login(request: HttpRequest, *args, **kwargs) ->
> None:
> print("Someone logged in successful - this would contain useful
> code")
> }}}
>
> Weirdly, as long as DEBUG is set to False, this code will run without
> problems. However, if DEBUG is turned to True, Signal.connect will use
> func_accepts_kwargs from django.utils.inspect to check if
> handle_successful_login accepts kwargs. func_accepts_kwargs will
> ultimatively use inspect.signature on the function, which triggers
> evaluation of the annotations and leads to NameError, as TYPE_CHECKING is
> False here.
>
> This can be resolved in various ways:
> 1. One can add from __future__ import annotations to switch back to
> Stringified annotations. However, this is called to be deprecated in the
> future
> 2. One can switch to always include HttpRequest. This would work, but
> code linters will fight this, argueing that HttpRequest is only used as
> an type annotation here (which is correct)
> 3. As django.utils.inspect does not actually care for the annotations,
> inspect.inspect(..., annotation_format=annotationlib.Format.STRING) can
> be used (sadly this works only in Python 3.14).
>
> My suggestion would be to something around
>
> {{{
> @functools.lru_cache(maxsize=512)
> def _get_func_parameters(func, remove_first):
> if sys.version_info[0:2] >= (3, 14):
> import annotationlib
> signature = inspect.signature(func,
> annotation_format=annotationlib.Format.STRING)
> else:
> signature = inspect.signature(func)
> parameters = tuple(signature.parameters.values())
> if remove_first:
> parameters = parameters[1:]
> return parameters
> }}}
>
> But I agree that it might not be the nicest solution.
New description:
Starting with Python 3.14, deferred evaluation of annotations (PEP-649) is
default now. This would suggest that using annotations in templatetags or
signals should be as easy as:
{{{
from typing import TYPE_CHECKING
from django.contrib.auth.signals import user_logged_in
from django.dispatch import receiver
if TYPE_CHECKING:
from django.http import HttpRequest
@receiver(user_logged_in)
def handle_successful_login(request: HttpRequest, *args, **kwargs) ->
None:
print("Someone logged in successful - this would contain useful code")
}}}
Weirdly, as long as DEBUG is set to False, this code will run without
problems. However, if DEBUG is turned to True, Signal.connect will use
func_accepts_kwargs from django.utils.inspect to check if
handle_successful_login accepts kwargs. func_accepts_kwargs will
ultimatively use inspect.signature on the function, which triggers
evaluation of the annotations and leads to NameError, as TYPE_CHECKING is
False here.
This can be resolved in various ways:
1. One can add from __future__ import annotations to switch back to
Stringified annotations. However, this is called to be deprecated in the
future
2. One can switch to always import HttpRequest. This would work, but code
linters will fight this, argueing that HttpRequest is only used as an type
annotation here (which is correct)
3. As django.utils.inspect does not actually care for the annotations,
inspect.inspect(..., annotation_format=annotationlib.Format.STRING) can be
used (sadly this works only in Python 3.14).
My suggestion would be to something around
{{{
@functools.lru_cache(maxsize=512)
def _get_func_parameters(func, remove_first):
if sys.version_info[0:2] >= (3, 14):
import annotationlib
signature = inspect.signature(func,
annotation_format=annotationlib.Format.STRING)
else:
signature = inspect.signature(func)
parameters = tuple(signature.parameters.values())
if remove_first:
parameters = parameters[1:]
return parameters
}}}
But I agree that it might not be the nicest solution.
--
Comment:
Thanks for the report. I might opt for `FORWARDREF` instead of `STRING`,
but otherwise I agree.
Would you like to submit a PR targeting main?
I think this should be backported as part of Python 3.14 support, as
otherwise you need to know to watch out for this gotcha when using a major
3.14 language feature.
--
Ticket URL: <https://code.djangoproject.com/ticket/36696#comment:1>
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