Weird output while structuring unions with custom disambiguation function

• cattrs version: 22.1.0
• Python version: 3.9

Description

Thanks for this amazing library !!

I am trying to write disambiguation function to handle union type based on the default value of child class but got into weird error, also want to understand the correct way to do it with cattrs.

@define(kw_only=True)
class GenType:
    pass

@define(kw_only=True)
class TypeOne(GenType):
    id:Literal["A"] = "A"


@define(kw_only=True)
class TypeTwo(GenType):
   id:Literal["B"] = "B"

UniType = Union[TypeOne, TypeTwo]

@define(kw_only=True)
class Container:
    types: List[UniType]

def discriminate_model_types(value: typing.Any, _klass: typing.Type) -> UniType:
    # Write some logic to find the exact type !!, I was wondering if there is correct pythonic version to do this with cattrs.
    for child_cls in GenType.__subclasses__():
        if value["id"] == child_cls().id:
            return cattr.structure(value, child_cls)

def run_union_logic():
    json = {"types":[{"id":"A"}]}
    cattr.register_structure_hook(UniType, discriminate_model_types)
    obj =cattr.structure(json, Container)
    print(obj)

    json = {"id": "A"}
    obj = cattr.structure(json, TypeOne)
    print(obj)

#Prints following:
#Container(types=[TypeOne()]) --> I dont know why property 'id' is not populated here. 
#TypeOne(id='A') 

Start by running the minimal example in the issue, especially run_union_logic and the registered UniType structure hook, then compare the Container result with direct TypeOne structuring. Determine why the union path omits the default id and establish the correct disambiguation behavior for the reported cattrs and Python versions.