Support hybrid_property, column_property, declared_attr

[50Bytes-dev]

    class Item(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        value: float
        hero_id: int = Field(foreign_key="hero.id")
        hero: "Hero" = Relationship(back_populates="items")

    class Hero(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        name: str
        items: list[Item] = Relationship(back_populates="hero")

        @hybrid_property
        def total_items(self):
            return sum([item.value for item in self.items], 0)

        @total_items.inplace.expression
        @classmethod
        def _total_items_expression(cls):
            return (
                select(func.coalesce(func.sum(Item.value), 0))
                .where(Item.hero_id == cls.id)
                .correlate(cls)
                .label("total_items")
            )

        @hybrid_property
        def status(self):
            return "active" if self.total_items > 0 else "inactive"

        @status.inplace.expression
        @classmethod
        def _status_expression(cls):
            return (
                select(case((cls.total_items > 0, "active"), else_="inactive"))
                .label("status")
            )

[50Bytes-dev]

    class Item(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        value: float
        hero_id: int = Field(foreign_key="hero.id")
        hero: "Hero" = Relationship(back_populates="items")

    class Hero(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        name: str
        items: List[Item] = Relationship(back_populates="hero")

        @declared_attr
        def total_items(cls):
            return column_property(cls._total_items_expression())

        @classmethod
        def _total_items_expression(cls):
            return (
                select(func.coalesce(func.sum(Item.value), 0))
                .where(Item.hero_id == cls.id)
                .correlate_except(Item)
                .label("total_items")
            )

        @declared_attr
        def status(cls):
            return column_property(
                select(
                    case(
                        (cls._total_items_expression() > 0, "active"), else_="inactive"
                    )
                ).scalar_subquery()
            )

[awoimbee]

Just small suggestions from a random outsider :p (some suggestions might be wrong).
All in all, this is clean and adds a lot of functionality, thanks !
You should look into this @tiangolo !

[muazhari]

Please merge it asap :3. I need it, lol.

[mfkaroui]

hey can we get this merged in

[mfkaroui]

@tiangolo Could you please take a look at this MR. The functionality is very nice. Would be a nice addition. Doesn't seem to clash with overall design

[francomahl]

    class Item(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        value: float
        hero_id: int = Field(foreign_key="hero.id")
        hero: "Hero" = Relationship(back_populates="items")

    class Hero(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        name: str
        items: List[Item] = Relationship(back_populates="hero")

        @declared_attr
        def total_items(cls):
            return column_property(cls._total_items_expression())

        @classmethod
        def _total_items_expression(cls):
            return (
                select(func.coalesce(func.sum(Item.value), 0))
                .where(Item.hero_id == cls.id)
                .correlate_except(Item)
                .label("total_items")
            )

        @declared_attr
        def status(cls):
            return column_property(
                select(
                    case(
                        (cls._total_items_expression() > 0, "active"), else_="inactive"
                    )
                ).scalar_subquery()
            )

Following this example I am getting

pydantic.errors.PydanticUserError: A non-annotated attribute was detected: `total_items = <sqlalchemy.orm.decl_api.declared_attr object at 0x10e415350>`. All model fields require a type annotation; if `total_items` is not meant to be a field, you may be able to resolve this error by annotating it as a `ClassVar` or updating `model_config['ignored_types']`.

Even if I do def total_items(cls): -> int I still get the same error.
SQLModel version 0.0.16

But I think we can get the same result with computed_field and the property decorator

    from pydantic import computed_field

    class Hero(SQLModel, table=True):
        id: Optional[int] = Field(default=None, primary_key=True)
        name: str
        items: List[Item] = Relationship(back_populates="hero")

        @computed_field
        @property
        def total_items(cls) -> int:
            return len(self.items)

[raphaellaude]

Any movement to get this functionality in?