Columns can't be a NewType, raises TypeError: issubclass() arg 1 must be a class

[rdozier-work]

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Example Code

import string

from typing import NewType
from typing import Annotated
from collections.abc import Iterable
from pydantic import StringConstraints
from pydantic import AfterValidator
from sqlmodel import SQLModel
from sqlmodel import Field
from sqlmodel import create_engine

def _validate_charset(s: str, charset: Iterable[str]) -> str:
    illegal_characters = set(s).difference(set(charset))
    assert (
            illegal_characters == {}
    ), f'string "{s}" contains illegal characters: {illegal_characters}'
    return s

PrintableString = Annotated[str, StringConstraints(max_length=16), AfterValidator(lambda s: _validate_charset(s, string.printable))]

# Suppose I also want a type called SpecialString to ensure during type checking that
# plain old PrintableStrings don't get confused for a SpecialString
SpecialString = NewType("SpecialString", PrintableString)

class MyModel(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    special_data: SpecialString

sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

if __name__ == "__main__":
    engine = create_engine(sqlite_url, echo=True)
    SQLModel.metadata.create_all(engine) # error! TypeError: issubclass() arg 1 must be a class

Description

I am trying to set up a database with SQLModel where some fields use typing.NewType. This does not change the runtime type at all, it is just a way to make certain subtypes distinct to a typechecker like Mypy.

If I run the example code, metadata.create_all() produces an error on line 571 of sqlmodel/main.py. The issue seems to be that issubclass() does not recognize a NewType as a class. Currently, I can get around the problem with:

# Suppose I also want a type called SpecialString to ensure during type checking that
# plain old PrintableStrings don't get confused for a SpecialString
if TYPE_CHECKING:
    SpecialString = NewType("SpecialString", PrintableString)
else:
    SpecialString = PrintableString

but that seems like explicitly checking TYPE_CHECKING kind of defeats the purpose of typing.NewType.

Operating System

macOS

Operating System Details

No response

SQLModel Version

0.0.19

Python Version

3.12.3

Additional Context

No response

[rdozier-work]

PS, looks like the same thing happens for Literal