SQLModel + Pydantic v1 vs SQLModel + Pydantic v2 - different assignment behaviour

[ta-soft]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the SQLModel documentation, with the integrated search.
• I already searched in Google "How to X in SQLModel" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

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Example Code

from pydantic import BaseModel
from sqlmodel import SQLModel, Field
from datetime import date
from typing import Optional


class A(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    dob: date

class B(BaseModel):
    dob: date

a=A(dob='1980-01-01')
print(a)
b=B(dob='1980-01-01')
print(b)

Description

The code above prints

id=None dob=datetime.date(1980, 1, 1)
dob=datetime.date(1980, 1, 1)

if executed with pydantic v1 in the mix (1)*.

But it prints

dob='1980-01-01' id=None
dob=datetime.date(1980, 1, 1)

With pydantic v2 in the mix (2)*.

This behaviour essentially breaks a fastapi application I am migrating to pedantic v2, because I assume, for example, that date attributes within objects passed in the body of post methods are already converted (originally passed as strings).

I couldn't find any recommendation related to this. I realize I could set table=False on the SQLModel object, but if I do that other behaviours change, related to validations for example.

Am I missing something?

(1) pyproject dependencies

python = "^3.10"
fastapi = "^0.110.0"
sqlmodel = "^0.0.16"
uvicorn = "^0.27.1"
pydantic = "1.10.14"

(2) pyproject deps

python = "^3.10"
fastapi = "^0.110.0"
sqlmodel = "^0.0.16"
uvicorn = "^0.27.1"
pydantic = "2.6.3"

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.16

Python Version

3.10

Additional Context

No response

[ta-soft]

note: adding

model_config = ConfigDict(validate_assignment=True)

to my models is not really an option, because that will make the code also start validating objects as soon as they are created, not allowing different attributes to be populated in phases (which is something I suspect a lot of people do frequently)

[Viicos]

Is your issue about the fact that in Pydantic v2, the dob attribute isn't parsed as a datetime.date object?

[ta-soft]

Generally speaking v2 + sqlmodel appear to not coerce/convert types where possible - and that is my issue

[ta-soft]

Any updates or thoughts on this one?

[YuriiMotov]

SQLModels with table=True bypass validation, you shouldn't use models with table=True for input validation.

Create ABase model, move common fields there and use it for validation:

from sqlmodel import SQLModel, Field
from datetime import date
from typing import Optional


class ABase(SQLModel):
    id: Optional[int] = Field(default=None, primary_key=True)
    dob: date


class A(ABase, table=True):
    pass


a = ABase(dob="1980-01-01")
print(a)  # id=None dob=datetime.date(1980, 1, 1)