Nested tagged unions?

[uar316025]

Question

Hi!
Can i do something like that?
(not sure how to name it)
Here example with pydantiic (v2)

First tagged union by type field
Then second by sub_type field

from typing import Literal, Annotated

import pydantic

class Device(pydantic.BaseModel):
    type: int
    sub_type: int
    name: str

class BlenderM1(Device):
    type: Literal[0x01] = 0x01
    sub_type: Literal[0x01] = 0x01

class BlenderM2(BlenderM1):
    sub_type: Literal[0x02] = 0x02

class OvenM1(Device):
    type: Literal[0x02] = 0x02
    sub_type: Literal[0x01] = 0x01

class OvenM2(OvenM1):
    sub_type: Literal[0x02] = 0x02

AnyDevice = Annotated[
    Annotated[BlenderM1 | BlenderM2, pydantic.Field(discriminator='sub_type')] |
    Annotated[OvenM1 | OvenM2, pydantic.Field(discriminator='sub_type')],
    pydantic.Field(discriminator='type')
]
print(pydantic.TypeAdapter(list[AnyDevice]).validate_python([
    {'type': 0x01, 'sub_type': 0x01, 'name': 'BM1'},
    {'type': 0x01, 'sub_type': 0x02, 'name': 'BM2'},
    {'type': 0x02, 'sub_type': 0x01, 'name': 'OM1'},
    {'type': 0x02, 'sub_type': 0x02, 'name': 'OM2'},
]))

which prints

[
  BlenderM1(type=1, sub_type=1, name='BM1'),
  BlenderM2(type=1, sub_type=2, name='BM2'),
  OvenM1(type=2, sub_type=1, name='OM1'),
  OvenM2(type=2, sub_type=2, name='OM2')
]

Also i can't change the devices structure because it is defined externally.