65 lines
2.2 KiB
Python
65 lines
2.2 KiB
Python
from __future__ import annotations
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from typing import TYPE_CHECKING, Any
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from attrs import NOTHING, Attribute, Factory
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from .._compat import is_bare_final
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from ..dispatch import StructureHook
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from ..errors import StructureHandlerNotFoundError
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from ..fns import raise_error
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if TYPE_CHECKING:
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from ..converters import BaseConverter
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def find_structure_handler(
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a: Attribute, type: Any, c: BaseConverter, prefer_attrs_converters: bool = False
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) -> StructureHook | None:
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"""Find the appropriate structure handler to use.
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Return `None` if no handler should be used.
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"""
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try:
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if a.converter is not None and prefer_attrs_converters:
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# If the user as requested to use attrib converters, use nothing
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# so it falls back to that.
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handler = None
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elif (
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a.converter is not None and not prefer_attrs_converters and type is not None
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):
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try:
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handler = c.get_structure_hook(type, cache_result=False)
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except StructureHandlerNotFoundError:
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handler = None
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else:
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# The legacy way, should still work.
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if handler == raise_error:
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handler = None
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elif type is not None:
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if (
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is_bare_final(type)
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and a.default is not NOTHING
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and not isinstance(a.default, Factory)
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):
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# This is a special case where we can use the
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# type of the default to dispatch on.
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type = a.default.__class__
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handler = c.get_structure_hook(type, cache_result=False)
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if handler == c._structure_call:
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# Finals can't really be used with _structure_call, so
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# we wrap it so the rest of the toolchain doesn't get
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# confused.
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def handler(v, _, _h=handler):
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return _h(v, type)
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else:
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handler = c.get_structure_hook(type, cache_result=False)
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else:
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handler = c.structure
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return handler
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except RecursionError:
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# This means we're dealing with a reference cycle, so use late binding.
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return c.structure
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