flake8-pydantic 0.1.0.post0

A flake8 plugin to check Pydantic related code.

Flake8 Pydantic

A flake8 plugin to check Pydantic related code.

Class detection

flake8_pydantic parses the AST to emit linting errors. As such, it cannot accurately determine if a class is defined as a Pydantic model. However, it tries its best, using the following heuristics:

• The class inherits from BaseModel or RootModel.
• The class has a model_config attribute set.
• The class has a field defined with the Field function.
• The class has a field making use of Annotated.
• The class makes use of Pydantic decorators, such as computed_field or model_validator.
• The class overrides any of the Pydantic methods, such as model_dump.

Error codes

PYD001 - Positional argument for Field default argument

Raise an error if the default argument of the Field function is positional.

class Model(BaseModel):
    foo: int = Field(1)

Although allowed at runtime by Pydantic, it does not comply with the typing specification (PEP 681) and type checkers will not be able to synthesize a correct __init__ method.

Instead, consider using an explicit keyword argument:

class Model(BaseModel):
    foo: int = Field(default=1)

PYD002 - Non-annotated attribute inside Pydantic model

Raise an error if a non-annotated attribute is defined inside a Pydantic model class.

class Model(BaseModel):
    foo = 1  # Will error at runtime

PYD010 - Usage of __pydantic_config__

Raise an error if a Pydantic configuration is set with __pydantic_config__.

class Model(TypedDict):
    __pydantic_config__ = {}  # Type checkers will emit an error

Although allowed at runtime by Python, type checkers will emit an error as it is not allowed to assign values when defining a TypedDict.

Instead, consider using the with_config decorator:

@with_config({"str_to_lower": True})
class Model(TypedDict):
    pass

And many more to come.

Roadmap

Once the rules of the plugin gets stable, the goal will be to implement them in Ruff, with autofixes when possible.