ensure_cls_attr_from_type_args

ensure_cls_attr_from_type_args#

tollan.utils.typing.ensure_cls_attr_from_type_args(cls: type, attr_name: str, max_depth: int = 2, bound: type | None = None, type_filter: type | None = None, *, skip_on_exist: bool = True, disallow_explicit: bool = True) → None[source]#

Ensure a class attribute is set from typing arguments.

Extract typing arguments from the class’s generic base classes and set the specified class attribute to the first matching argument.

Parameters:

  • cls (type) – Class to set attribute on

  • attr_name (str) – Name of the class attribute to set

  • max_depth (int, optional) – Maximum depth to traverse the class hierarchy. Default is 2.

  • bound (type | None, optional) – Filter typing arguments to only include subclasses of this type

  • type_filter (type | None, optional) – Filter typing arguments to only include instances of this type

  • skip_on_exist (bool, optional) – If True, do not overwrite the attribute if it already exists.

  • disallow_explicit (bool, optional) – If True, raise TypeError if the attribute is explicitly set on cls (not inherited). Forces use of type parameters for consistency. Default is True to enforce consistency.

Raises:

  • TypeError – If disallow_explicit=True and attribute is explicitly set on cls.

  • ValueError – If no matching typing argument is found, or if multiple are found.

Notes

This function is useful for automatically setting class attributes based on Generic[T] type parameters, particularly in frameworks that use generics for configuration or dependency injection.

Examples

>>> from typing import Generic, TypeVar
>>> from pydantic import BaseModel
>>> T = TypeVar('T')
>>> class MyHandler(Generic[T]):
...     pass
>>> class MyConfig(BaseModel):
...     pass
>>> class ConcreteHandler(MyHandler[MyConfig]):
...     pass
>>> ensure_cls_attr_from_type_args(
...     ConcreteHandler, 'config_model_cls', bound=BaseModel
... )
>>> ConcreteHandler.config_model_cls
<class '...MyConfig'>
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