generated from daniil-berg/boilerplate-py
31 lines
1.1 KiB
Python
31 lines
1.1 KiB
Python
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from typing import Any, Generic, Optional, TypeVar, get_args, get_origin
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_T = TypeVar("_T")
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class GenericInsightMixin(Generic[_T]):
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_type_arg: Optional[type[_T]] = None
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@classmethod
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def __init_subclass__(cls, **kwargs: Any) -> None:
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"""Saves the type argument in the `_type_arg` class attribute."""
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super().__init_subclass__(**kwargs)
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for base in cls.__orig_bases__: # type: ignore[attr-defined]
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origin = get_origin(base)
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if origin is None or not issubclass(origin, GenericInsightMixin):
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continue
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type_arg = get_args(base)[0]
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# Do not set the attribute for GENERIC subclasses!
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if not isinstance(type_arg, TypeVar):
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cls._type_arg = type_arg
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return
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@classmethod
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def _get_type_arg(cls) -> type[_T]:
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"""Returns the type argument of the class (if specified)."""
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if cls._type_arg is None:
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raise AttributeError(
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f"{cls.__name__} is generic; type argument unspecified"
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)
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return cls._type_arg
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