Mypy issue 'name <func> already defined' when using hybrid property and expression of sqlalchemy

Is the a way to solve the issue with mypy and sqlalchemy when defining the expresison of a hybrid property, it triggered name <func> already defined

class User(Base):
    first_name: Mapped[str] = mapped_column(String(100), nullable=False)
    last_name: Mapped[str] = mapped_column(String(100), nullable=False)

    @hybrid_property
    def name(self) -> str:
        return f"{self.first_name} {self.last_name}"

    @full_name.expression
    def name(cls) -> str:
        return cls.first_name + " " + cls.last_name

I don’t want to install external stubs package or ignore it with # type : ignore.
Is there a way to rename the expression or something else ?

>Solution :

I’ve faced a similar issue with mypy when using SQLAlchemy’s hybrid_property. The problem arises because you’re defining the method name twice: once as an instance method and once as a class method for the expression, which causes mypy to report a duplicate definition error.

To resolve this without installing external stubs or using # type: ignore, you can rename the expression method and explicitly assign it to the hybrid_property. Here’s how you can modify your code:

from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

class Base(DeclarativeBase):
    pass

class User(Base):
    __tablename__ = 'user'

    id: Mapped[int] = mapped_column(primary_key=True)
    first_name: Mapped[str] = mapped_column(String(100), nullable=False)
    last_name: Mapped[str] = mapped_column(String(100), nullable=False)

    def _get_name(self) -> str:
        return f"{self.first_name} {self.last_name}"

    @classmethod
    def _name_expr(cls):
        return cls.first_name + " " + cls.last_name

    name = hybrid_property(fget=_get_name, expr=_name_expr)

By defining _get_name and _name_expr with different names, you avoid redefining name, and mypy won’t complain about duplicate definitions. Then, you assign them to the hybrid_property named name.

This approach keeps your code clean and type-safe without suppressing type checking or adding external packages.