Dataclasses <> sqlalchemy dataclass mapping <> Pydantic dataclass is not working

[sandys]

from datetime import datetime

from sqlalchemy import (
    Column,
    DateTime,
    Integer,
    String,
    Table,
    ARRAY,
)

from typing import Optional

from dataclasses import dataclass
from dataclasses import field, dataclass
from sqlalchemy.orm import registry, relationship

import pydantic

mapper_registry = registry()


@mapper_registry.mapped
@dataclass
class Stock:
    __table__ = Table(
        "stocks",
        mapper_registry.metadata,
        Column("id", Integer, primary_key=True, index=True),
        Column("dt", DateTime, index=True),
        Column("symbol", String(5), nullable=False, index=True),
        Column("company", String(50), index=True),
        Column("price", Integer),
    )
    id: int = field(init=False)
    price: int = field(init=False)
    dt: datetime = field(default_factory=datetime)
    symbol: Optional[str] = None
    company: Optional[str] = None

    def __repr__(self):
        return f"""<Stock(id={self.id}, 
                        datetime={self.dt}, 
                        company={self.company}, 
                        symbol={self.symbol}, 
                        price={self.price})>\n"""


StockRequest = pydantic.dataclasses.dataclass(Stock)

the code for this was taken from sqlalchemy 1.4 dataclass support (https://docs.sqlalchemy.org/en/14/orm/mapping_styles.html#declarative-mapping-with-dataclasses-and-attrs) as well as pydantic dataclass support (https://pydantic-docs.helpmanual.io/usage/dataclasses/)

The error I get is TypeError: cannot pickle 'getset_descriptor' object.

Can someone help - what is the right way to create a single dataclass and use it interoperably in sqlalchemy as well pydantic ?

[sandys]

The other style also doesnt work

from datetime import datetime

from sqlalchemy import (
    Column,
    DateTime,
    Integer,
    String,
    Table,
    ARRAY,
)

from typing import Optional

from dataclasses import dataclass
from dataclasses import field, dataclass
from sqlalchemy.orm import registry, relationship

import pydantic

mapper_registry = registry()


@mapper_registry.mapped
@dataclass
class Stock2:
    __tablename__ = "stock2"
    __sa_dataclass_metadata_key__ = "sa"
    id: int = field(init=False, metadata={"sa": Column(Integer, primary_key=True)})
    price: int = field(init=False, metadata={"sa": Column(Integer)})
    dt: datetime = field(default_factory=datetime, metadata={"sa": Column(DateTime)})
    symbol: Optional[str] = field(default=None, metadata={"sa": Column(String(50))})
    company: Optional[str] = field(default=None, metadata={"sa": Column(String(50))})


StockRequest = pydantic.dataclasses.dataclass(Stock2)

the issue seems to be the @mapper_registry.mapped decorator