44 lines
1.5 KiB
Python
44 lines
1.5 KiB
Python
from __future__ import annotations
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from typing import TypeVar
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from .._compat import get_args, get_origin, is_generic
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def generate_mapping(cl: type, old_mapping: dict[str, type] = {}) -> dict[str, type]:
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mapping = {}
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origin = get_origin(cl)
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if origin is not None:
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# To handle the cases where classes in the typing module are using
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# the GenericAlias structure but aren't a Generic and hence
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# end up in this function but do not have an `__parameters__`
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# attribute. These classes are interface types, for example
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# `typing.Hashable`.
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parameters = getattr(get_origin(cl), "__parameters__", None)
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if parameters is None:
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return dict(old_mapping)
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for p, t in zip(parameters, get_args(cl)):
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if isinstance(t, TypeVar):
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continue
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mapping[p.__name__] = t
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if not mapping:
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return dict(old_mapping)
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elif is_generic(cl):
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# Origin is None, so this may be a subclass of a generic class.
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orig_bases = cl.__orig_bases__
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for base in orig_bases:
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if not hasattr(base, "__args__"):
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continue
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base_args = base.__args__
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if not hasattr(base.__origin__, "__parameters__"):
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continue
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base_params = base.__origin__.__parameters__
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for param, arg in zip(base_params, base_args):
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mapping[param.__name__] = arg
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return mapping
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