Typing issue on selectinload() expected "Literal['*'] | QueryableAttribute[Any]"

[copdips]

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Example Code

query = select(User).options(selectinload(User.team)).offset(offset).limit(limit)

Description

Hello,

I'm running a one-to-many, Team to User classic relationship.

Table User declares field team_id which is a FK to Team.id. and relationship team for loading.

class User(SQLModel, table=True)
    ...
    team_id: str | None = Field(
        default=None,
        foreign_key="team.id",
    }
    team: Team | None = Relationship(back_populates="users")

All is good, except a MyPy typing error on selectinload() method:

error: Argument 1 to "selectinload" has incompatible type "Team | None"; 
expected "Literal['*'] | QueryableAttribute[Any]"  [arg-type]

When using:

from sqlalchemy.orm import selectinload

query = select(User).options(selectinload(User.team)).offset(offset).limit(limit)

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.16
SQLAlchemy 2.0.29

Python Version

Python 3.11.7

Additional Context

No response

[AlPashy]

Have you solved it?, cause i get the same exception

[copdips]

sorry nope

[itsbekas]

Hey 🙂 As a note for the future, please try to provide a minimal, reproducible example. Following the Discussion Guidelines is important to help us help you.

This is my attempt at recreating your situation:

from sqlmodel import Field, Relationship, SQLModel, create_engine, Session, select
from sqlalchemy.orm import selectinload

class Team(SQLModel, table=True):
    id: int = Field(primary_key=True)
    name: str = Field()
    users: list["User"] = Relationship(back_populates="team")

class User(SQLModel, table=True):
    name: str = Field(primary_key=True)
    team_id: str | None = Field(
        default=None,
        foreign_key="team.id",
    )
    team: Team | None = Relationship(back_populates="users")

engine = create_engine("sqlite:///example.db")
SQLModel.metadata.create_all(engine)

team1 = Team(name="Team Rocket")

user1 = User(name="Jessie", team=team1)
user2 = User(name="James", team=team1)

with Session(engine) as session:
    session.add(team1)
    session.add(user1)
    session.commit()

    query = select(User).options(selectinload(User.team)).offset(1).limit(1)

    users = session.exec(query)

    print([r for r in users])

However, this version runs as-is without any issues (I used SQLModel 0.0.16 and SQLAlchemy 2.0.29, but I'm using Python 3.12, though I doubt that's the cause). If your use-case is different, feel free to modify this example to better illustrate it 🙂 Maybe you can show us yours as well @AlPashy

[AlPashy]

I have implemented the recreation from you and mypy says:
load.py:30: error: Argument 1 to "selectinload" has incompatible type "Team | None"; expected "Literal['*'] | QueryableAttribute[Any]" [arg-type]

newest sqlalchemy, sqlmodel version with python 3.11. Is there a alternative to solve this?

[copdips]

I tested in 3.12.2 with new venv (pip install sqlmodel mypy), same error

[itsbekas]

You're both right, I apologize. For some reason mypy wasn't picking up that error on my side.

In the meantime, I think I found the issue:
By changing team: Team | None to team: Mapped[Team | None] (note that Mapped is imported from sqlalchemy.orm), the error seems to disappear, while the example still works as intended. However, I'm not sure if this has any side effects, namely with Pydantic (assuming you're using FastAPI), so you might want to check that, just to be sure.

[copdips]

great, no more mypy errors, also tested with my fastapi, all good, thanks a lot for this solution.