Faulty Pyright error on frozen daughters (frozen=True) of non-frozen parents (frozen=False)

[caniko]

Initial Checks

• I have searched Google & GitHub for similar requests and couldn't find anything
• I have read and followed the docs and still think this feature is missing

Description

Some of my models used in FastAPI come from 3rd party libraries like fastapi-users; here the models are frozen=False. Currently, I can actually freeze them, but pyright errors.

Idea:

class MyModel(BaseModel, frozen=False):
     a: int

class MyDaughter(MyModel, frozen=True):
    b: int

This gives the following pyright error:

error: A frozen class cannot inherit from a class that is not frozen

Affected Components

• Compatibility between releases
• Data validation/parsing
• Data serialization - .model_dump() and .model_dump_json()
• JSON Schema
• Dataclasses
• Model Config
• Field Types - adding or changing a particular data type
• Function validation decorator
• Generic Models
• Other Model behaviour - model_construct(), pickling, private attributes, ORM mode
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.

[sydney-runkle]

@caniko,

What happens with dataclasses? I'm guessing we'd want to mimick that behavior...

[caniko]

@sydney-runkle

Pydantic base models can actually inherit from frozen to non-frozen, but the issue is pyright. Pyright treats BaseModel as dataclass in this instance. Dataclass inheritance from frozen to non-frozen is impossible; however, not the case for BaseModel.

[wikiped]

pyright's dev point of view