Pydantic default values test in version 1.10

pydantic_1_10.py

from decimal import Decimal
from typing import Optional

from pydantic import BaseModel, root_validator
from pydantic.fields import SHAPE_SINGLETON, ModelField


class CustomBaseModel(BaseModel):

    @staticmethod
    def is_optional(field: ModelField):
        if field.allow_none and (field.shape != SHAPE_SINGLETON or not field.sub_fields):
            return True

        return False

    @root_validator(pre=True)
    def set_default_value_with_optional_field(cls, values: dict):
        for k, field in cls.__fields__.items():
            default = field.get_default()
            if cls.is_optional(field) and default is not None:
                v = values.pop(k, None)
                values[k] = default if v is None else v

        return values


class DefaultUser(BaseModel):
    id: int
    name: Optional[str] = 'kobe'
    coin: Optional[int] = 100
    number: Optional[Decimal] = Decimal('0.1')
    items: Optional[list[str]] = []


class CustomUser(CustomBaseModel):
    id: int
    name: Optional[str] = 'kobe'
    coin: Optional[int] = 100
    number: Optional[Decimal] = Decimal('0.1')
    items: Optional[list[str]] = []


print(DefaultUser(id=1))
# >>> id=1 name='kobe' coin=100 number=Decimal('0.1') items=[]

print(CustomUser(id=1))
# >>> id=1 name='kobe' coin=100 number=Decimal('0.1') items=[]

print(DefaultUser(id=1, name=None, coin=None, number=None, items=None))
# >>> id=1 name=None coin=None number=None items=None

print(CustomUser(id=1, name=None, coin=None, number=None, items=None))
# >>> id=1 name='kobe' coin=100 number=Decimal('0.1') items=[]

Pydantic default values test in version 1.10.

Demonstrates how DefaultUser and CustomUser handle not provided
values versus None. DefaultUser applies standard Pydantic behavior,
while CustomUser uses a custom root validator to override None with defaults.