[BUG] Pydantic's StringConstraint not working as expected in SQLModel

[mubarakalmehairbi]

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Example Code

from pydantic import BaseModel
from sqlmodel import SQLModel, Field
from typing_extensions import Annotated
from pydantic.types import StringConstraints

UsernameStr = Annotated[str, StringConstraints(strip_whitespace=True, to_lower=True)]

class NormalModel(BaseModel):
    username: UsernameStr

class SqlModel(SQLModel, table=True):
    id: str = Field(primary_key=True)
    username: UsernameStr

print(f"Normal: {NormalModel(username='ABC')}")
print(f"Sql: {SqlModel(username='ABC')}")

Description

The expected output is:

Normal: username='abc'
Sql: username='abc'

where in both cases the username is in lower case.

However, the output is:

Normal: username='abc'
Sql: username='ABC'

Notice that pydantic converted the username to lower case while sqlmodel didnt.
Note that this only happens if table=True.

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.24

Python Version

3.10.0

Additional Context

No response

[YuriiMotov]

This is because of table=True. Such "table"-models bypass validation on instantiation.

You can use SqlModel.model_validate({"username": 'ABC'}) instead of SqlModel(username='ABC').

But conventional approach is to use separate model\models for input and output data validation:

from typing import Optional

from pydantic.types import StringConstraints
from sqlmodel import Field, SQLModel
from typing_extensions import Annotated

UsernameStr = Annotated[str, StringConstraints(strip_whitespace=True, to_lower=True)]

class SqlModelBase(SQLModel):
    username: UsernameStr

class SqlModelCreate(SqlModelBase):
    pass

class SqlModel(SqlModelBase, table=True):
    id: Optional[str] = Field(default=None, primary_key=True)

a_input = SqlModelCreate(username='ABC')
a = SqlModel.model_validate(a_input)
print(f"Sql: {a}")  # Sql: id=None username='abc'

Read more: #52 (comment)