Dataclass Mapping changed in sqalchemy 2.0

[PaleNeutron]

Refer: https://docs.sqlalchemy.org/en/20/orm/dataclasses.html#orm-declarative-native-dataclasses

Current documented dataclass style is:

from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.orm import Mapped
from sqlalchemy.orm import mapped_column
from sqlalchemy.orm import MappedAsDataclass


class Base(MappedAsDataclass, DeclarativeBase):
    """subclasses will be converted to dataclasses"""


class User(Base):
    __tablename__ = "user_account"

    id: Mapped[int] = mapped_column(init=False, primary_key=True)
    name: Mapped[str]

or at least:

from sqlalchemy.orm import Mapped
from sqlalchemy.orm import mapped_column
from sqlalchemy.orm import registry


reg = registry()


@reg.mapped_as_dataclass
class User:
    __tablename__ = "user_account"

    id: Mapped[int] = mapped_column(init=False, primary_key=True)
    name: Mapped[str]

Columns type should be Mapped[int] not int which is different with current sqlacodegen and the new mapped_column is much more readable.

[agronholm]

Yeah, this needs updating. I'm not going to be working on this project for a little while (I have a queue of more urgent issues to address) so a PR would go a long way towards addressing this.

[andrew222651]

Try latest master

[Franky1]

Or try RC versions from pypi, for example: pip install "sqlacodegen==3.0.0rc3"
https://pypi.org/project/sqlacodegen/#history

[NixBiks]

init=False is not being set in dataclasses generator for automatic id's e.g. (and relations). I think that's a mistake, no?

[agronholm]

How then would you explicitly set the primary key value on insert?

[NixBiks]

True. But how would you let the server set it otherwise? You are not allowed to make an instance without the id

[agronholm]

This is a dilemma I haven't been able to figure out yet. As you probably know, SQLAlchemy really lets you do it either way, and it's just the annotations that are the issue here.

[NixBiks]

Yeah I was just trying to figure out if it's possible. Doesn't seem like it. They don't really mention anything about it in the docs.

[sheinbergon]

@agronholm looks like the main issue / feature request have already been dealt with.
About the follow up discussion regarding setting init=False on autogenerated fields, I'm actually on board with @NixBiks.
IMO conceptually speaking, meeting generated value constraints set up and maintained by the database should not be a data-class concern

[sheinbergon]

@agronholm looks like the main issue / feature request have already been dealt with. About the follow up discussion regarding setting init=False on autogenerated fields, I'm actually on board with @NixBiks. IMO conceptually speaking, meeting generated value constraints set up and maintained by the database should not be a data-class concern

@agronholm can we discuss this?

[agronholm]

I'm fine with going with whatever the SQLAlchemy docs recommend.