type casting does not work with multiple attributes of the same custom type #7102
Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
I tried to upgrade a custom data type from pydantic v1 to v2.
It looks like the type casting works as long as there is only one attribute of the type assigned to a model.
When there are two, a validation error is raised:
ValidationError: 1 validation error for Test2
y
Input should be a valid dictionary or instance of Numeric [type=model_type, input_value=2, input_type=int]
For further information visit https://errors.pydantic.dev/2.1/v/model_typeI attached a minimal example down below.
Maybe the schema generation isn't done as it should be. I am happy to add some more documentation if someone guides me to the right solution for this example
Example Code
from typing import Any, Self
import pydantic
from pydantic_core import CoreSchema, core_schema
class Numeric(pydantic.BaseModel):
value: float
unit: str = "m"
@classmethod
def __get_pydantic_core_schema__(
cls, source_type: Any, handler: pydantic.GetCoreSchemaHandler
) -> CoreSchema:
return core_schema.no_info_before_validator_function(cls.validate, handler(source_type))
@classmethod
def validate(cls, v: Any) -> dict[str, Any] | Self:
if isinstance(v, (str, float, int)):
return cls(value=v)
elif isinstance(v, Numeric):
if v.unit == cls.unit:
return v
elif isinstance(v, dict):
return v
raise ValueError(f"Invalid value for {cls}: {v}")
class Test1(pydantic.BaseModel):
x: Numeric
class Test2(pydantic.BaseModel):
x: Numeric
y: Numeric
print("test1:", Test1(x=2))
print("test2:", Test2(x=2, y=2))Python, Pydantic & OS Version
pydantic version: 2.1.1
pydantic-core version: 2.4.0
pydantic-core build: profile=release pgo=true mimalloc=true
install path: /home/xxx/.local/lib/python3.11/site-packages/pydantic
python version: 3.11.3 (main, Jun 5 2023, 09:32:32) [GCC 13.1.1 20230429]
platform: Linux-6.4.7-arch1-1-x86_64-with-glibc2.37
optional deps. installed: ['typing-extensions']
Selected Assignee: @Kludex