sqlalchemy_descriptor_name.py

"""Test whether a descriptor's __set_name__ is called in multiple scenarios."""

from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base, declared_attr

Base = declarative_base()
db = SQLAlchemy()


class Descriptor:
    def __init__(self):
        self.name = 'name-not-set'

    def __set_name__(self, owner, name):
        self.name = name

    def __get__(self, obj, cls=None):
        return self


class Metaclass(type):
    def __new__(cls, name, bases, dct):
        return super().__new__(cls, name, bases, dct)


class SimpleClass:
    attr = Descriptor()


class WithMetaclass(metaclass=Metaclass):
    attr = Descriptor()


class BaseModel(Base):
    __tablename__ = 'base_model'
    id = Column(Integer, primary_key=True)

    attr = Descriptor()


class FlaskModel(db.Model):
    __tablename__ = 'flask_model'
    id = Column(Integer, primary_key=True)

    attr = Descriptor()


class SubBaseModel(SimpleClass, Base):
    __tablename__ = 'sub_base_model'
    id = Column(Integer, primary_key=True)


class SubFlaskModel(SimpleClass, db.Model):
    __tablename__ = 'sub_flask_model'
    id = Column(Integer, primary_key=True)


class Mixin:
    @declared_attr
    def attr(cls):
        return Descriptor()


class MixinBaseModel(Mixin, Base):
    __tablename__ = 'mixin_base_model'
    id = Column(Integer, primary_key=True)


class MixinFlaskModel(Mixin, db.Model):
    __tablename__ = 'mixin_flask_model'
    id = Column(Integer, primary_key=True)


if __name__ == '__main__':
    instances = [
        SimpleClass(),
        WithMetaclass(),
        BaseModel(),
        FlaskModel(),
        SubBaseModel(),
        SubFlaskModel(),
        MixinBaseModel(),
        MixinFlaskModel(),
    ]

    for i in instances:
        print(i.__class__.__name__, i.attr.name)

Output:

SimpleClass attr
WithMetaclass attr
BaseModel attr
FlaskModel attr
SubBaseModel attr
SubFlaskModel attr
MixinBaseModel name-not-set
MixinFlaskModel name-not-set