cattrs

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• cattrs version: cattrs version: 22.1.0
• Python version: 3.10
• Operating System: MacOS Monterey 12.2.1

Description

I tried to structure some data into the union type with keys renaming. It doesn't work because the default disambiguation function creator builds it based on non-overriden fields (link). I could write a proper disambiguator myself but I think it should work out-of-the-box.

What I Did

from attrs import define
import cattrs
from cattrs.gen import make_dict_structure_fn, override

@define
class A:
    a_field: int


@define
class B:
    another_field: int


c = cattrs.GenConverter()

c.register_structure_hook(A, make_dict_structure_fn(A, c, a_field=override(rename="aField")))
c.register_structure_hook(B, make_dict_structure_fn(B, c, another_field=override(rename="anotherField")))

print(c.structure({'aField': 1}, A))
# A(a_field=1)

print(c.structure({'anotherField': 1}, B))
# B(another_field=1)

print(c.structure({'anotherField': 1}, A | B))
# B(another_field=1)

print(c.structure({'aField': 1}, A | B))
# raises ClassValidationError: While structuring B (1 sub-exception)
# ClassValidationError('While structuring B', [KeyError('another_field')])

I just ran into this as well with the exact same use case. Using rename to convert from snake case to camel case and my union type gets incorrectly disambiguated.