Warn if anything marked as deprecated is used

[mamekoro]

Python 3.13 introduced a decorator called @warnings.deprecated that marks classes, functions and methods as deprecated. For older versions of Python, @deprecated.deprecated is available as an alternative.

Would you consider adding the functionality to warn of the use of objects marked as deprecated by these decorators? In other words, a feature like that provided by memestra.

[sbrugman]

In general such a rule could be a great addition for library developers that want to do a quick check of expired deprecations before a release. Warning users of such functions would require multi-file analysis.

In practice, many libraries define their own deprecation decorator with additional functionality such as version and expiry information. My impression is that for popular packages it's more common to use a custom decorator than that to use the standard library (warnings) or a third-party (deprecated).

Since we cannot detect these custom implementations reliably, we could consider letting the user configure fully qualified names of the deprecation functions, like https://docs.astral.sh/ruff/settings/#lint_flake8-boolean-trap_extend-allowed-calls. This would make this rule effective for those users too.

Examples:

• https://github.com/astropy/astropy/blob/main/astropy/cosmology/flrw/base.py#L111
• https://github.com/apache/airflow/blob/main/providers/src/airflow/providers/google/cloud/operators/mlengine.py#L82
• https://github.com/flet-dev/flet/blob/main/sdk/python/packages/flet/src/flet/core/page.py#L726
• https://github.com/langchain-ai/langchain/blob/master/libs/core/langchain_core/tracers/schemas.py#L31
• https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/eager/profiler.py#L62
• https://github.com/apache/superset/blob/master/superset/views/base.py#L375
• https://github.com/conda/conda/blob/main/conda/exports.py#L112
• https://github.com/ray-project/ray/blob/master/python/ray/runtime_context.py#L22

[MichaReiser]

That makes sense but it does require multifile analysis. For now, you could consider using https://docs.astral.sh/ruff/rules/banned-api/