SQLAlchemy/SQLModel Relationship Error: sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper[Users(users)]' has no property 'user'

[bilal-dev-bit]

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.

Commit to Help

• I commit to help with one of those options 👆

Example Code

#users.py from model package

import uuid
from enum import Enum
from typing import TYPE_CHECKING, List

from pydantic import EmailStr
from sqlmodel import SQLModel, Field, Relationship
from sqlalchemy.orm import Mapped,relationship

from backend.app.models._base import TimeStampMixin

if TYPE_CHECKING:
    from backend.app.models.orders import Orders
    from backend.app.models.cart import Cart
    from backend.app.models.addresses import Address
    from backend.app.models.reviews import Review
    from backend.app.models.wishlist import Wishlist


class UserRole(str, Enum):
    USER = "user"
    ADMIN = "admin"


class UsersBase(TimeStampMixin):
    username: str = Field(index=True, min_length=4)
    email: EmailStr
    role: UserRole


class UsersCreate(UsersBase):
    password: str = Field(min_length=8)


class UsersUpdate(SQLModel):
    username: str | None = None
    password: str | None = None
    email: EmailStr | None = None
    role: UserRole | None = None


class UsersPublic(UsersBase):
    id: uuid.UUID


class Users(UsersBase, table=True):
    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True, index=True)
    hashed_password: str

    ##relationships 1-M
    orders: List["Orders"] = Relationship(
        sa_relationship=relationship(back_populates="user"),
        cascade_delete=True,
        passive_deletes=True,

    )
    carts: Mapped[List["Cart"]] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
    reviews: Mapped[List["Review"]] = Relationship(back_populates="user", passive_deletes=True)
    wishlists: Mapped[List["Wishlist"]] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
    addresses: Mapped[List["Address"]] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
##end of users.py model
##order.py model
import uuid
from decimal import Decimal
from enum import Enum
from typing import TYPE_CHECKING, Optional, List

from sqlmodel import Field, SQLModel, Relationship
from sqlalchemy.orm import Mapped,relationship

from backend.app.models._base import TimeStampMixin

if TYPE_CHECKING:
    from backend.app.models.users import Users
    from backend.app.models.order_items import OrderItem


class OrderStatus(str, Enum):
    PENDING = "pending"
    SHIPPED = "shipped"
    DELIVERED = "delivered"
    CANCELLED = "cancelled"


class OrdersBase(TimeStampMixin):
    user_id: uuid.UUID = Field(foreign_key="users.id", ondelete="CASCADE")
    total_amount: Decimal = Field(ge=1, decimal_places=2)
    status: OrderStatus = Field(default=OrderStatus.PENDING)


class OrdersCreate(OrdersBase):
    pass


class OrdersPublic(OrdersBase):
    id: uuid.UUID


class OrdersUpdate(SQLModel):
    total_amount: Decimal | None = None
    status: OrderStatus | None = None


class Orders(OrdersBase, table=True):
    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True, index=True)

    ##relationship M-1
    user:Mapped[Optional["Users"]] = Relationship(
        sa_relationship=relationship(back_populates="orders")

    )
    order_items:Mapped[List["OrderItem"]] = Relationship(back_populates="order", cascade_delete=True, passive_deletes=True)
##end of order.py 
## orders.py service package
from sqlmodel import Session

from backend.app.core.db import engine
from backend.app.models.orders import Orders, OrdersCreate

def add_order(order_data: OrdersCreate):
    with Session(engine) as session:
        order_db = Orders.model_validate(order_data)

        session.add(order_db)
        session.commit()
        session.refresh(order_db)
        print(order_db)

add_order({
    "total_amount": 2000,
    "status": "PENDING"
})

Description

I’m encountering an error when trying to define and use relationships between my Orders and Users models using SQLModel. The error occurs when I attempt to create an order with a relationship to a user. The error message is:
sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper[Users(users)]' has no property 'user'.

I’ve verified that the database tables are created correctly, and the relationships seem to be defined properly. However, SQLAlchemy is unable to resolve the user property in the Users model at runtime.
Code Snippets:

orders.py

import uuid
from decimal import Decimal
from enum import Enum
from typing import TYPE_CHECKING, Optional, List

from sqlmodel import Field, SQLModel, Relationship

from backend.app.models._base import TimeStampMixin

if TYPE_CHECKING:
    from backend.app.models.users import Users
    from backend.app.models.order_items import OrderItem


class OrderStatus(str, Enum):
    PENDING = "pending"
    SHIPPED = "shipped"
    DELIVERED = "delivered"
    CANCELLED = "cancelled"


class OrdersBase(TimeStampMixin):
    user_id: uuid.UUID = Field(foreign_key="users.id", ondelete="CASCADE")
    total_amount: Decimal = Field(ge=1, decimal_places=2)
    status: OrderStatus = Field(default=OrderStatus.PENDING)


class OrdersCreate(OrdersBase):
    pass


class OrdersPublic(OrdersBase):
    id: uuid.UUID


class OrdersUpdate(SQLModel):
    total_amount: Decimal | None = None
    status: OrderStatus | None = None


class Orders(OrdersBase, table=True):
    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True, index=True)

    ##relationship M-1
    user: Optional["Users"] = Relationship(back_populates="orders")
    order_items: List["OrderItem"] = Relationship(back_populates="order", cascade_delete=True, passive_deletes=True)

users.py

import uuid
from enum import Enum
from typing import TYPE_CHECKING, List

from pydantic import EmailStr
from sqlmodel import SQLModel, Field, Relationship

from backend.app.models._base import TimeStampMixin

if TYPE_CHECKING:
    from backend.app.models.orders import Orders
    from backend.app.models.cart import Cart
    from backend.app.models.addresses import Address
    from backend.app.models.reviews import Review
    from backend.app.models.wishlist import Wishlist


class UserRole(str, Enum):
    USER = "user"
    ADMIN = "admin"


class UsersBase(TimeStampMixin):
    username: str = Field(index=True, min_length=4)
    email: EmailStr
    role: UserRole


class UsersCreate(UsersBase):
    password: str = Field(min_length=8)


class UsersUpdate(SQLModel):
    username: str | None = None
    password: str | None = None
    email: EmailStr | None = None
    role: UserRole | None = None


class UsersPublic(UsersBase):
    id: uuid.UUID


class Users(UsersBase, table=True):
    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True, index=True)
    hashed_password: str

    ##relationships 1-M
    orders: List["Orders"] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
    carts: List["Cart"] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
    reviews: List["Review"] = Relationship(back_populates="user", passive_deletes=True)
    wishlists: List["Wishlist"] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)
    addresses: List["Address"] = Relationship(back_populates="user", cascade_delete=True, passive_deletes=True)

orders.py from services package

from sqlmodel import Session

from backend.app.core.db import engine
from backend.app.models.orders import Orders, OrdersCreate

def add_order(order_data: OrdersCreate):
    with Session(engine) as session:
        order_db = Orders.model_validate(order_data)

        session.add(order_db)
        session.commit()
        session.refresh(order_db)
        print(order_db)

add_order({
    "total_amount": 2000,
    "status": "PENDING"
})

gives an error on order_db = Orders.model_validate(order_data)
"
error message "sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper[Users(users)]' has no property 'user'. If this property was indicated from other mappers or configure events, ensure registry.configure() has been called.
"

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.22

Python Version

3.12.8

Additional Context

No response