#35667: Switch warnings.warn usage to skip_file_prefixes instead of stacklevel
-------------------------------------+-------------------------------------
Reporter: Simon Charette | Type:
| Cleanup/optimization
Status: new | Component: Utilities
Version: 5.1 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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In most of our usages of `warnings.warn` (and almost every usage that
relates to deprecation warnings) we want them to be associated to the
first out-of-as that's the most likely location that can be adjusted to
avoid the warning.
In order to achieve this goal we've historically attempted to pass a fixed
`stacklevel` to `warnings.warn` which can sometimes
[https://github.com/django/django/blob/f16a9a556fb4225f9094048614f4fcec3db7e067/django/conf/__init__.py#L146-L153
be tricky] and [https://code.djangoproject.com/ticket/35666 error prone]
depending on how nested and convoluted the user or third-party app
offending call site might be. In other cases
[https://github.com/django/django/commit/fbd16438f46bc2128926958ad24331da5d1b406f
we've opted not to] provide a `stacklevel` at all as determining the
offending call site under all circumstances is impossible.
Well it appears that this is a problem that Python 3.12 allows frameworks
to address in a better way with
[https://docs.python.org/3/library/warnings.html#warnings.warn the
introduction of] `warnings.warn(skip_file_prefixes: tuple[str] | None)`.
This new feature would allow us to ensure that the proper offending call
site is referenced when emitting from a deeply nested call site where
`stacklevel` is inappropriate.
Since this is a Python 3.12+ feature I'd suggest we introduce a
`get_non_django_stacklevel() -> int` (better name welcome) function that
could be used to pass to `warnings.warn(stacklevel)` until we drop support
for Python 3.11.
--
Ticket URL: <https://code.djangoproject.com/ticket/35667>
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