Using regexes to filter warnings

[Nikratio]

Hi,

I have so far been using Python code to configure warning filters (rather than $PYTHONWARNINGS, -W, or filterwarnings in pytest.ini) because this enables me to use regular expression to select modules.

My use case is that I would like to see all Deprecation warnings that can be fixed in the application that I'm testing, but not in modules that I do not control. With regular expressions, I can just match on the top-level module name. Without regular expression, I need to hardcode every module and sub-module.

Unfortunately, I have just discovered that pytest has been messing with my warning configuration despite me using the -p no:warnings flag (see #10847 for a related problem).

Is there any way to use pytest's own warnings facilities with regular expressions for the module?

[Aneesh495]

Yes: the module field in filterwarnings config entries supports regular expressions. For an application package named myapp, you can ignore dependency deprecations and then enable the application's own deprecations:

[pytest]
filterwarnings =
    ignore::DeprecationWarning
    default::DeprecationWarning:^myapp(\.|$)

Replace myapp with your top-level package. The last matching filter wins, so keep the broad ignore first. The boundary matches myapp and myapp.submodule, while excluding names such as myapplication.

Keep pytest's warnings plugin enabled for this; remove -p no:warnings. The regex support here differs from CLI -W / PYTHONWARNINGS, whose module field is a literal module name. Also, filtering uses the module attributed to the warning after stacklevel is applied, not every module on its call stack.

I checked this on Python 3.14 / pytest 9.2.0 with warnings emitted in myapp.api, thirdparty, and myapplication: only the myapp.api deprecation appeared. See the warning filter documentation and precedence rules.

Prepared with Codex assistance; the config behavior above was checked locally.

[Icaro0310]

The module field in the filterwarnings spec is already a regex, matched against the start of the fully qualified module name. Same syntax as -W and warnings.filterwarnings, so you don't need Python code for this:

[pytest]
filterwarnings =
 ignore::DeprecationWarning
 default::DeprecationWarning:myapp(\..*)?$

Later lines win, so this silences DeprecationWarnings everywhere, then turns them back on for your package. Use always instead of default if you want every occurrence rather than the first per location.

If a dep still leaks through, print warning.filename/__name__ in a pytest.warning_recorded hook or just check python -W behavior, the module name there is the __name__ of the file raising it, which sometimes isn't what you'd expect for re-exported code.

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