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ODMantic schema generation fails with discriminated unions #509

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MickVermeulen opened this issue Dec 5, 2024 · 0 comments
Open

ODMantic schema generation fails with discriminated unions #509

MickVermeulen opened this issue Dec 5, 2024 · 0 comments
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bug Something isn't working

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@MickVermeulen
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MickVermeulen commented Dec 5, 2024 •
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Bug

When using discriminated unions in a ODMantic model, it raises a schema generation error where vanilla pydantic does not.

Current Behavior

from odmantic import Model, SyncEngine
from pydantic import Field, BaseModel
from typing import Literal, TypeAlias, Annotated


class Cat(BaseModel):
    mice_eaten: int
    pet_type: Literal["cat"] = "cat"


class Dog(BaseModel):
    balls_caught: int
    pet_type: Literal["dog"] = "dog"


Pet: TypeAlias = Annotated[
    Cat | Dog,
    Field(discriminator="pet_type"),
]


class HouseholdPydantic(BaseModel):
    pets: list[Pet]


# Uncomment this and it will crash
# class HouseholdODMantic(Model):
#     pets: list[Pet]


if __name__ == "__main__":
    instance = HouseholdPydantic(pets=[Cat(mice_eaten=5), Dog(balls_caught=3)])
    print(instance.model_json_schema())

    # Uncomment this and it will crash
    # engine = SyncEngine()
    # instance = HouseholdODMantic(pets=[Cat(mice_eaten=5), Dog(balls_caught=3)])
    # print(instance.model_json_schema())
    # engine.save(instance)

If you uncomment the commented out lines, this will raise:

Traceback (most recent call last):
  File "/Users/user/myproject/odmantic_test.py", line 26, in <module>
    class HouseholdODMantic(Model):
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/odmantic/model.py", line 487, in __new__
    return super().__new__(mcs, name, bases, namespace, **kwargs)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/odmantic/model.py", line 405, in __new__
    cls = super().__new__(mcs, name, bases, namespace, **kwargs)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_model_construction.py", line 205, in __new__
    complete_model_class(
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_model_construction.py", line 534, in complete_model_class
    schema = cls.__get_pydantic_core_schema__(cls, handler)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/main.py", line 643, in __get_pydantic_core_schema__
    return handler(source)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_schema_generation_shared.py", line 83, in __call__
    schema = self._handler(source_type)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 512, in generate_schema
    schema = self._generate_schema_inner(obj)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 784, in _generate_schema_inner
    return self._model_schema(obj)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 591, in _model_schema
    {k: self._generate_md_field_schema(k, v, decorators) for k, v in fields.items()},
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 591, in <dictcomp>
    {k: self._generate_md_field_schema(k, v, decorators) for k, v in fields.items()},
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 947, in _generate_md_field_schema
    common_field = self._common_field_schema(name, field_info, decorators)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 1134, in _common_field_schema
    schema = self._apply_annotations(
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 1890, in _apply_annotations
    schema = get_inner_schema(source_type)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_schema_generation_shared.py", line 83, in __call__
    schema = self._handler(source_type)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 1972, in new_handler
    schema = metadata_get_schema(source, get_inner_schema)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_std_types_schema.py", line 316, in __get_pydantic_core_schema__
    items_schema = handler.generate_schema(self.item_source_type)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_schema_generation_shared.py", line 97, in generate_schema
    return self._generate_schema.generate_schema(source_type)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 512, in generate_schema
    schema = self._generate_schema_inner(obj)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 789, in _generate_schema_inner
    return self.match_type(obj)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 871, in match_type
    return self._match_generic_type(obj, origin)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 919, in _match_generic_type
    return self._unknown_type_schema(obj)
  File "/Users/user/.pyenv/versions/miniconda3-latest/envs/myenv/lib/python3.10/site-packages/pydantic/_internal/_generate_schema.py", line 415, in _unknown_type_schema
    raise PydanticSchemaGenerationError(
pydantic.errors.PydanticSchemaGenerationError: Unable to generate pydantic-core schema for typing.Annotated[types.UnionType[__main__.Cat, __main__.Dog], FieldInfo(annotation=NoneType, required=True, discriminator='pet_type')]. Set `arbitrary_types_allowed=True` in the model_config to ignore this error or implement `__get_pydantic_core_schema__` on your type to fully support it.

If you got this error by calling handler(<some type>) within `__get_pydantic_core_schema__` then you likely need to call `handler.generate_schema(<some type>)` since we do not call `__get_pydantic_core_schema__` on `<some type>` otherwise to avoid infinite recursion.

For further information visit https://errors.pydantic.dev/2.8/u/schema-for-unknown-type

If you keep the lines commented out, the schema prints fine.

Environment

  • Python version: 3.10
  • ODMantic version: 1.0.2
  • Pydantic version: 2.8.2, pydantic-core version: 2.20.1
@MickVermeulen MickVermeulen added the bug Something isn't working label Dec 5, 2024
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@MickVermeulen