validate_assignment fixes setter type coercion problem

validate_assignment_fixes_setter.py

import pytest
from pydantic import BaseModel, ValidationError


class Pizza(BaseModel):
    toppings_count: int
    size: str

    class Config:  # 1
        validate_assignment = True  # 2


def test_pydantic_allows_setters_conversions():
    pizza = Pizza(toppings_count='4', size='XL')
    assert pizza.toppings_count == 4
    pizza.toppings_count = '5'  # 3
    assert pizza.toppings_count == 5  #  3
    with pytest.raises(ValidationError):  # 4
        pizza.toppings_count = 'no conversion'  # 4