BaseSettings raises `TypeError` for set/frozenset config attributes in 2.5.0

[daria-shaw]

After updating to pydantic-settings 2.5.0, I found that setting a attribute of a BaseSettings class to frozenset[str] or set[str] would raise TypeError: issubclass() arg 1 must be a class, which looks to have been introduced in this commit

MWE

from pydantic_settings import BaseSettings


class ExampleConfig(BaseSettings):
    dependencies_to_build_badges: frozenset[str] = frozenset({
        "dep_1",
        "dep_2",
    })


def test_config_init():
    ExampleConfig()

traceback from the example

    def test_config_init():
>       ExampleConfig()

tests/test_benchmark_runner.py:12:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
.venv/lib/python3.10/site-packages/pydantic_settings/main.py:153: in __init__
    **__pydantic_self__._settings_build_values(
.venv/lib/python3.10/site-packages/pydantic_settings/main.py:357: in _settings_build_values
    source_state = source()
.venv/lib/python3.10/site-packages/pydantic_settings/sources.py:545: in __call__
    field_value = self.prepare_field_value(field_name, field, field_value, value_is_complex)
.venv/lib/python3.10/site-packages/pydantic_settings/sources.py:738: in prepare_field_value
    is_complex, allow_parse_failure = self._field_is_complex(field)
.venv/lib/python3.10/site-packages/pydantic_settings/sources.py:771: in _field_is_complex
    if self.field_is_complex(field):
.venv/lib/python3.10/site-packages/pydantic_settings/sources.py:276: in field_is_complex
    return _annotation_is_complex(field.annotation, field.metadata)
.venv/lib/python3.10/site-packages/pydantic_settings/sources.py:2118: in _annotation_is_complex
    if isinstance(annotation, type) and issubclass(annotation, RootModel):
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

cls = <class 'pydantic.root_model.RootModel'>, subclass = set[str]

    def __subclasscheck__(cls, subclass):
        """Override for issubclass(subclass, cls)."""
>       return _abc_subclasscheck(cls, subclass)
E       TypeError: issubclass() arg 1 must be a class

../../.pyenv/versions/3.10.13/lib/python3.10/abc.py:123: TypeError

[hramezani]

Thanks @daara-s for reporting.

It seems a duplicate of #390

I already fixed it and it's included in pydantic-settings 2.5.1. Could you update pydantic-settings to the latest version and try it again?

[hramezani]

Closing this issue and we can follow on #390

[hramezani]

Here is the patch.

It would be great if you can confirm the fix

[daria-shaw]

apologies for the delay, takes some time for pypi to sync with work's artifactory. 2.5.1 didn't fix the issue.

[daria-shaw]

Recreated my example in the patch branch, and it worked.

[hramezani]

Got released in pydantic-settings 2.5.2

Thanks for helping!