Subclass identification error on a one to one relationship.

[Lolozendev]

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Example Code

from pydantic import BaseModel, computed_field, HttpUrl, model_serializer, model_validator
from typing import Annotated, Optional, Any, Self

from sqlalchemy.orm import Relationship
from sqlmodel import SQLModel, Field, BigInteger, AutoString

class Color(BaseModel):
    red: int
    green: int
    blue: int

class User(SQLModel, table=True):
    id: int = Field(primary_key=True, sa_type=BigInteger)
    name: str

    habitue: Optional["Habitue"] = Relationship(back_populates="user",uselist=False)
    streamer: Optional["Streamer"] = Relationship(back_populates="user",uselist=False)

class Habitue(SQLModel, table=True):
    id_: int | None = Field(primary_key=True, default=None)
    user_id: int = Field(foreign_key="user.id", sa_type=BigInteger)
    color: Color = Field(sa_type=AutoString)

    user: User = Relationship(back_populates="habitue")

class Streamer(SQLModel, table=True):
    id_: int | None = Field(primary_key=True, default=None)
    user_id: int = Field(foreign_key="user.id", sa_type=BigInteger)
    url: HttpUrl

    user: User = Relationship(back_populates="streamer")

We wanted to be as close as possible to this scenario, even if it's not the best way to do it with sql:

CREATE TABLE user (
    id BIGINT PRIMARY KEY,
    name TEXT NOT NULL
);

CREATE TABLE habitue (
    id_ SERIAL PRIMARY KEY,
    user_id BIGINT UNIQUE NOT NULL,
    color TEXT NOT NULL,
    FOREIGN KEY (user_id) REFERENCES user(id) ON DELETE CASCADE
);

CREATE TABLE streamer (
    id_ SERIAL PRIMARY KEY,
    user_id BIGINT UNIQUE NOT NULL,
    url TEXT NOT NULL,
    FOREIGN KEY (user_id) REFERENCES user(id) ON DELETE CASCADE
);

Description

We have a User class with an Id and a name.To represent whether this user is a “Streamer” or a “Habitue”, we've defined two other classes with their own attributes.

For us, a “User” has the optional ability to be a “Habitue” (A "Habitue" has a color) and/or a “Streamer” (a "Streamer" has a url). We therefore try to represent this link between a basic “User” and its advanced versions via a One-to-One relationship.

We realize that at runtime, a type comparison is made. The “Streamer” and “Habitue” classes are not recognized as subclasses of the SQLModel type, but as Enums.As a result, we are unable to establish this One-to-One relationship.

Traceback (most recent call last):

  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 784, in _load_from_module_spec
    spec.loader.exec_module(lib)  # type: ignore
    │    │      │           └ <module 'cogs.startup' from '/app/cogs/startup.py'>
    │    │      └ <function _LoaderBasics.exec_module at 0x7fdc23d7ade0>
    │    └ <_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>
    └ ModuleSpec(name='cogs.startup', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>, origin='/app/c...
  File "<frozen importlib._bootstrap_external>", line 1026, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed

  File "/app/cogs/startup.py", line 4, in <module>
    from models.db_schemas import User, Habitue, Color, Streamer

  File "/app/models/db_schemas.py", line 50, in <module>
    class User(SQLModel, table=True):
               └ <class 'sqlmodel.main.SQLModel'>

  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 559, in __new__
    col = get_column_from_field(v)
          │                     └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
          └ <function get_column_from_field at 0x7fdc205ab100>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 708, in get_column_from_field
    sa_type = get_sqlalchemy_type(field)
              │                   └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
              └ <function get_sqlalchemy_type at 0x7fdc205ab060>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 656, in get_sqlalchemy_type
    if issubclass(type_, Enum):
                  │      └ <enum 'Enum'>
                  └ ForwardRef('Habitue')

TypeError: issubclass() arg 1 must be a class

To try to solve this, we tried the recommendations provided in:

• Add one-to-one relationship tutorial to docs #381
• Error when using Relationships with one-to-one models #132

Operating System

Linux

Operating System Details

I'm running it in a python3.13 image docker

SQLModel Version

0.0.22

Python Version

Python 3.13.2

Additional Context

Full StackTrace:

Traceback (most recent call last):

  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 784, in _load_from_module_spec
    spec.loader.exec_module(lib)  # type: ignore
    │    │      │           └ <module 'cogs.startup' from '/app/cogs/startup.py'>
    │    │      └ <function _LoaderBasics.exec_module at 0x7fdc23d7ade0>
    │    └ <_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>
    └ ModuleSpec(name='cogs.startup', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>, origin='/app/c...
  File "<frozen importlib._bootstrap_external>", line 1026, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed

  File "/app/cogs/startup.py", line 4, in <module>
    from models.db_schemas import User, Habitue, Color, Streamer

  File "/app/models/db_schemas.py", line 50, in <module>
    class User(SQLModel, table=True):
               └ <class 'sqlmodel.main.SQLModel'>

  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 559, in __new__
    col = get_column_from_field(v)
          │                     └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
          └ <function get_column_from_field at 0x7fdc205ab100>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 708, in get_column_from_field
    sa_type = get_sqlalchemy_type(field)
              │                   └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
              └ <function get_sqlalchemy_type at 0x7fdc205ab060>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 656, in get_sqlalchemy_type
    if issubclass(type_, Enum):
                  │      └ <enum 'Enum'>
                  └ ForwardRef('Habitue')

TypeError: issubclass() arg 1 must be a class


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


Traceback (most recent call last):

  File "/app/main.py", line 105, in <module>
    run(main())
    │   └ <function main at 0x7fdc20607420>
    └ <function run at 0x7fdc234ca700>

  File "/usr/local/lib/python3.13/asyncio/runners.py", line 195, in run
    return runner.run(main)
           │      │   └ <coroutine object main at 0x7fdc20564440>
           │      └ <function Runner.run at 0x7fdc234587c0>
           └ <asyncio.runners.Runner object at 0x7fdc206838c0>
  File "/usr/local/lib/python3.13/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           │    │     │                  └ <Task pending name='Task-1' coro=<main() running at /app/.venv/lib/python3.13/site-packages/loguru/_logger.py:1282> cb=[_run_...
           │    │     └ <function BaseEventLoop.run_until_complete at 0x7fdc234562a0>
           │    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
           └ <asyncio.runners.Runner object at 0x7fdc206838c0>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 712, in run_until_complete
    self.run_forever()
    │    └ <function BaseEventLoop.run_forever at 0x7fdc23456200>
    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 683, in run_forever
    self._run_once()
    │    └ <function BaseEventLoop._run_once at 0x7fdc23458040>
    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 2040, in _run_once
    handle._run()
    │      └ <function Handle._run at 0x7fdc234954e0>
    └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
> File "/usr/local/lib/python3.13/asyncio/events.py", line 89, in _run
    self._context.run(self._callback, *self._args)
    │    │            │    │           │    └ <member '_args' of 'Handle' objects>
    │    │            │    │           └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
    │    │            │    └ <member '_callback' of 'Handle' objects>
    │    │            └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
    │    └ <member '_context' of 'Handle' objects>
    └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>

  File "/app/main.py", line 101, in main
    zors_bot = await ZORS.create_bot()
                     │    └ <classmethod(<function ZORS.create_bot at 0x7fdc23bfc9a0>)>
                     └ <class '__main__.ZORS'>

  File "/app/main.py", line 46, in create_bot
    bot = ZORS(
          └ <class '__main__.ZORS'>

  File "/app/main.py", line 25, in __init__
    self._load_cogs()
    │    └ <function ZORS._load_cogs at 0x7fdc205e0a40>
    └ <__main__.ZORS object at 0x7fdc21f327b0>

  File "/app/main.py", line 74, in _load_cogs
    status = self.load_extensions("cogs", recursive=True, store=False)
             │    └ <function CogMixin.load_extensions at 0x7fdc221cbba0>
             └ <__main__.ZORS object at 0x7fdc21f327b0>

  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 1025, in load_extensions
    loaded = self.load_extension(
             │    └ <function CogMixin.load_extension at 0x7fdc221cb920>
             └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 933, in load_extension
    loaded = self.load_extension(
             │    └ <function CogMixin.load_extension at 0x7fdc221cb920>
             └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 918, in load_extension
    self._load_from_module_spec(spec, name)
    │    │                      │     └ 'cogs.startup'
    │    │                      └ ModuleSpec(name='cogs.startup', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>, origin='/app/c...
    │    └ <function CogMixin._load_from_module_spec at 0x7fdc221cb600>
    └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 787, in _load_from_module_spec
    raise errors.ExtensionFailed(key, e) from e
          │      │               └ 'cogs.startup'
          │      └ <class 'discord.errors.ExtensionFailed'>
          └ <module 'discord.errors' from '/app/.venv/lib/python3.13/site-packages/discord/errors.py'>

discord.errors.ExtensionFailed: Extension 'cogs.startup' raised an error: TypeError: issubclass() arg 1 must be a class

Traceback (most recent call last):

  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 784, in _load_from_module_spec
    spec.loader.exec_module(lib)  # type: ignore
    │    │      │           └ <module 'cogs.startup' from '/app/cogs/startup.py'>
    │    │      └ <function _LoaderBasics.exec_module at 0x7fdc23d7ade0>
    │    └ <_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>
    └ ModuleSpec(name='cogs.startup', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>, origin='/app/c...
  File "<frozen importlib._bootstrap_external>", line 1026, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed

  File "/app/cogs/startup.py", line 4, in <module>
    from models.db_schemas import User, Habitue, Color, Streamer

  File "/app/models/db_schemas.py", line 50, in <module>
    class User(SQLModel, table=True):
               └ <class 'sqlmodel.main.SQLModel'>

  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 559, in __new__
    col = get_column_from_field(v)
          │                     └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
          └ <function get_column_from_field at 0x7fdc205ab100>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 708, in get_column_from_field
    sa_type = get_sqlalchemy_type(field)
              │                   └ FieldInfo(annotation=Union[ForwardRef('Habitue'), NoneType], required=False, default=<Relationship at 0x7fdc1efcf390; no key>)
              └ <function get_sqlalchemy_type at 0x7fdc205ab060>
  File "/app/.venv/lib/python3.13/site-packages/sqlmodel/main.py", line 656, in get_sqlalchemy_type
    if issubclass(type_, Enum):
                  │      └ <enum 'Enum'>
                  └ ForwardRef('Habitue')

TypeError: issubclass() arg 1 must be a class


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


Traceback (most recent call last):

  File "/app/main.py", line 105, in <module>
    run(main())
    │   └ <function main at 0x7fdc20607420>
    └ <function run at 0x7fdc234ca700>

  File "/usr/local/lib/python3.13/asyncio/runners.py", line 195, in run
    return runner.run(main)
           │      │   └ <coroutine object main at 0x7fdc20564440>
           │      └ <function Runner.run at 0x7fdc234587c0>
           └ <asyncio.runners.Runner object at 0x7fdc206838c0>
  File "/usr/local/lib/python3.13/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           │    │     │                  └ <Task pending name='Task-1' coro=<main() running at /app/.venv/lib/python3.13/site-packages/loguru/_logger.py:1282> cb=[_run_...
           │    │     └ <function BaseEventLoop.run_until_complete at 0x7fdc234562a0>
           │    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
           └ <asyncio.runners.Runner object at 0x7fdc206838c0>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 712, in run_until_complete
    self.run_forever()
    │    └ <function BaseEventLoop.run_forever at 0x7fdc23456200>
    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 683, in run_forever
    self._run_once()
    │    └ <function BaseEventLoop._run_once at 0x7fdc23458040>
    └ <_UnixSelectorEventLoop running=True closed=False debug=False>
  File "/usr/local/lib/python3.13/asyncio/base_events.py", line 2040, in _run_once
    handle._run()
    │      └ <function Handle._run at 0x7fdc234954e0>
    └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
> File "/usr/local/lib/python3.13/asyncio/events.py", line 89, in _run
    self._context.run(self._callback, *self._args)
    │    │            │    │           │    └ <member '_args' of 'Handle' objects>
    │    │            │    │           └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
    │    │            │    └ <member '_callback' of 'Handle' objects>
    │    │            └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>
    │    └ <member '_context' of 'Handle' objects>
    └ <Handle <_asyncio.TaskStepMethWrapper object at 0x7fdc20fa71f0>()>

  File "/app/main.py", line 101, in main
    zors_bot = await ZORS.create_bot()
                     │    └ <classmethod(<function ZORS.create_bot at 0x7fdc23bfc9a0>)>
                     └ <class '__main__.ZORS'>

  File "/app/main.py", line 46, in create_bot
    bot = ZORS(
          └ <class '__main__.ZORS'>

  File "/app/main.py", line 25, in __init__
    self._load_cogs()
    │    └ <function ZORS._load_cogs at 0x7fdc205e0a40>
    └ <__main__.ZORS object at 0x7fdc21f327b0>

  File "/app/main.py", line 74, in _load_cogs
    status = self.load_extensions("cogs", recursive=True, store=False)
             │    └ <function CogMixin.load_extensions at 0x7fdc221cbba0>
             └ <__main__.ZORS object at 0x7fdc21f327b0>

  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 1025, in load_extensions
    loaded = self.load_extension(
             │    └ <function CogMixin.load_extension at 0x7fdc221cb920>
             └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 933, in load_extension
    loaded = self.load_extension(
             │    └ <function CogMixin.load_extension at 0x7fdc221cb920>
             └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 918, in load_extension
    self._load_from_module_spec(spec, name)
    │    │                      │     └ 'cogs.startup'
    │    │                      └ ModuleSpec(name='cogs.startup', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7fdc1f38bbf0>, origin='/app/c...
    │    └ <function CogMixin._load_from_module_spec at 0x7fdc221cb600>
    └ <__main__.ZORS object at 0x7fdc21f327b0>
  File "/app/.venv/lib/python3.13/site-packages/discord/cog.py", line 787, in _load_from_module_spec
    raise errors.ExtensionFailed(key, e) from e
          │      │               └ 'cogs.startup'
          │      └ <class 'discord.errors.ExtensionFailed'>
          └ <module 'discord.errors' from '/app/.venv/lib/python3.13/site-packages/discord/errors.py'>

discord.errors.ExtensionFailed: Extension 'cogs.startup' raised an error: TypeError: issubclass() arg 1 must be a class