Bug: using custom registry causes runtime exception

[theunkn0wn1]

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Example Code

from sqlmodel import SQLModel, Field
from sqlalchemy.orm import registry

my_registry = registry()


class MyTable(SQLModel, table=True, registry=my_registry):
    foo: int = Field(primary_key=True)


def test_my_table_init():
    MyTable(foo=4)

# if invoking outside pytest
if __name__ == "__main__":
    test_my_table_init()

Description

When passing Sqlmodel an existing registry, any attempt to instantiate Sqlmodel types will fail with an exception.

In my case, i have a large production application I am attempting to migrate incrementally, using a mix of old classes mapped and sqlmodel new.

As such, i already have instances of Sqlalchemy metadata, registry objects that i wish to reuse.

The exception:

=============================================================================================================================== test session starts ===============================================================================================================================
platform linux -- Python 3.10.11, pytest-8.2.0, pluggy-1.5.0
rootdir: /tmp/something
collected 1 item                                                                                                                                                                                                                                                                  

test_sqlmodel.py F                                                                                                                                                                                                                                                          [100%]

==================================================================================================================================== FAILURES =====================================================================================================================================
_______________________________________________________________________________________________________________________________ test_my_table_init ________________________________________________________________________________________________________________________________

cls = <class 'test_sqlmodel.MyTable'>

    def manager_of_class(cls):
        try:
>           return cls.__dict__[DEFAULT_MANAGER_ATTR]
E           KeyError: '_sa_class_manager'

sqlmodel_venv/lib/python3.10/site-packages/sqlalchemy/orm/base.py:336: KeyError

The above exception was the direct cause of the following exception:

    def test_my_table_init():
>       MyTable(foo=4)

test_sqlmodel.py:12: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
sqlmodel_venv/lib/python3.10/site-packages/sqlmodel/main.py:723: in __init__
    sqlmodel_init(self=__pydantic_self__, data=data)
sqlmodel_venv/lib/python3.10/site-packages/sqlmodel/_compat.py:348: in sqlmodel_init
    sqlmodel_table_construct(
sqlmodel_venv/lib/python3.10/site-packages/sqlmodel/_compat.py:267: in sqlmodel_table_construct
    setattr(self_instance, key, value)
sqlmodel_venv/lib/python3.10/site-packages/sqlmodel/main.py:731: in __setattr__
    if is_table_model_class(self.__class__) and is_instrumented(self, name):  # type: ignore[no-untyped-call]
sqlmodel_venv/lib/python3.10/site-packages/sqlalchemy/orm/instrumentation.py:708: in is_instrumented
    return manager_of_class(instance.__class__).is_instrumented(
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

cls = <class 'test_sqlmodel.MyTable'>

    def manager_of_class(cls):
        try:
            return cls.__dict__[DEFAULT_MANAGER_ATTR]
        except KeyError as ke:
>           raise exc.UnmappedClassError(
                cls, f"Can't locate an instrumentation manager for class {cls}"
            ) from ke
E           sqlalchemy.orm.exc.UnmappedClassError: Can't locate an instrumentation manager for class <class 'test_sqlmodel.MyTable'>

sqlmodel_venv/lib/python3.10/site-packages/sqlalchemy/orm/base.py:338: UnmappedClassError
============================================================================================================================= short test summary info =============================================================================================================================
FAILED test_sqlmodel.py::test_my_table_init - sqlalchemy.orm.exc.UnmappedClassError: Can't locate an instrumentation manager for class <class 'test_sqlmodel.MyTable'>
================================================================================================================================ 1 failed in 0.38s ================================================================================================================================

Operating System

Linux

Operating System Details

$ cat /etc/os-release
PRETTY_NAME="Ubuntu 22.04.4 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.4 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy

SQLModel Version

0.0.18

Python Version

Python 3.10.11

Additional Context

Translating the entirety of my application to Sqlmodel in one shot is prohibitively expensive, especially as i am unsure I can achieve feature-parity with the existing sqlalchemy implementation.