What is the best way to validate a field using ormar + pydantic

[igormorgado]

I would like to validate some fields, for example, username fields larger than 3 characters. What is the best way to handle this. If possible please show me an example. Here is a small snippet to start with:

import databases
import ormar as orm
import sqlalchemy
import pydantic
from passlib.hash import bcrypt

DATABASE_URL = 'sqlite:///db.sqlite'
database = databases.Database(DATABASE_URL)
metadata = sqlalchemy.MetaData()

class User(orm.Model):
    class Meta(orm.ModelMeta):
         metadata = metadata
         database = database

    id: int = orm.Integer(primary_key=True)
    username: str = orm.String(max_length=64)
    password: str = orm.String(max_length=64)


class UserResponse(pydantic.BaseModel):
    class Config:
        orm_mode = True

    username: str
    # We are returning the password here for testing purposes only... ;-)
    password: str


async def create_user(username: str, password: str) -> UserResponse:
    user_new = User(username=username, password=bcrypt.hash(password))
    await user_new.save()
    # Lets check if user was really saved...
    user_result = await User.objects.filter(username=username).get()
    return UserResponse.from_orm(user_result)


async def main():
    engine = sqlalchemy.create_engine(DATABASE_URL)
    await database.connect()
    metadata.drop_all(engine)
    metadata.create_all(engine)

    user_new = await create_user(username='john', password='mysecretpass')
    print(user_new.json(indent=4))

    await database.disconnect()

if __name__ == '__main__':
    import asyncio
    asyncio.run(main())

Of course I could check the len(username) everywhere I need. But I would like to know the best way to couple that to the model.

[collerek]

For each field in ormar you can use all of the pydantic Field arguments (https://pydantic-docs.helpmanual.io/usage/schema/#field-customisation).

So in you case simply add min_length argument to ormar string field.

If your definition of pydantic Field is very fancy, you can force replace the field: https://collerek.github.io/ormar/fields/common-parameters/#overwrite_pydantic_type.