extend from a class with json fields but raise error: <class 'list'> has no matching SQLAlchemy type

[Ka2e]

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Example Code

from sqlmodel import SQLModel, Field, Column
from sqlalchemy import JSON


class User(SQLModel, table=True):
    __tablename__ = "t_user"
    id: int = Field(primary_key=True)
    num_list: list = Field(default=[], sa_column=Column(JSON))


class UserInfo(User, table=False):
    info: str | None = Field(default="")

Description

I have some class extends from sqlmodel class with json fields, but it raise error:

\venv\Lib\site-packages\sqlmodel\main.py", line 697, in get_sqlalchemy_type
    raise ValueError(f"{type_} has no matching SQLAlchemy type")
ValueError: <class 'list'> has no matching SQLAlchemy type

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.21

Python Version

3.11

Additional Context

No response

[vlavorini]

Hello, same issue here, even with a simpler model like:

from sqlmodel import create_engine, SQLModel, Session, Field


class Example(SQLModel, table=True):
    file_path: str = Field(default=None, primary_key=True)
    person_number: int
    person_list: list[str]


engine = create_engine("postgresql://....", echo=True)
SQLModel.metadata.create_all(engine)

to_rec = Example(file_path="asd",
                        person_number=2,
                        person_list=['a', 'b'])
with Session(engine) as session:
    session.add(to_rec)
    session.commit()

Running with
SQLModel 0.0.21
sqlalchemy 2.0.32
Pydantic 2.5.2
python 3.10 on Linux

[KunxiSun]

Hello! Glad I can help.@Ka2e @vlavorini
Do that 👇🏻

from sqlmodel import (
    SQLModel,
    Field,
    Column,
    JSON,
)


class User(SQLModel, table=True):
    __tablename__ = "t_user"
    id: int = Field(primary_key=True)
    num_list: list = Field(default=[], sa_type=JSON)

The magic here is to use the field sa_type.

[vlavorini]

Indeed it works!

For completeness, I changed it a bit to exploit the PostgreSQL backend:

num_list: list[str] = Field(default=None, sa_type=ARRAY(Text))

[Ka2e]

Thanks for your answer.
If we only use class User，it works well.
But if we declare a class UserInfo extend from class User, the error still exist:

from sqlmodel import (
    SQLModel,
    Field,
    JSON,
)


class User(SQLModel, table=True):
    __tablename__ = "t_user"
    id: int = Field(primary_key=True)
    num_list: list = Field(default=[], sa_type=JSON)


class UserInfo(User, table=False):
    info: str | None = Field(default="")

ValueError: <class 'list'> has no matching SQLAlchemy type

[KunxiSun]

Thanks for your answer. If we only use class User，it works well. But if we declare a class UserInfo extend from class User, the error still exist:

from sqlmodel import (
    SQLModel,
    Field,
    JSON,
)


class User(SQLModel, table=True):
    __tablename__ = "t_user"
    id: int = Field(primary_key=True)
    num_list: list = Field(default=[], sa_type=JSON)


class UserInfo(User, table=False):
    info: str | None = Field(default="")

ValueError: <class 'list'> has no matching SQLAlchemy type

Oh, I missed your point. The output shows it is an error of inheriting from the database model.

I did meet this bug before, then I solve it by not inherit from the database model.

I split the model into different functions. I have:
BaseModel: has all shared field
ModelIn: responsible for the input data
Model: responsible for the database model, including foreign key, relationships
ModelPublic: responsible for the data output

So in your case, it will be 👇🏻

from somewhere import id_factory
from sqlmodel import (
    SQLModel,
    Field,
    JSON,
)

class BaseUser(SQLModel):
    """Have all the shared fields of Input, database model, and output"""
    id: int = Field(primary_key=True, default=id_factory)
    num_list: list = Field(default=[], sa_type=JSON)

class UserIn(BaseUser):
    """Accept responsible for the input from frontend"""

class User(BaseUser, table=True):
    """Database model"""

class UserPublic(BaseUser):
    """Output for frontend"""
    info: str | None = Field(default="")