python.pydantic.arbitrary_types

Correctness Medium

Detects Pydantic models using arbitrary_types_allowed without proper validation.

Why It Matters

Arbitrary types without validation:

• No type checking — Complex types not validated
• Serialization errors — Can’t convert to JSON
• Hidden bugs — Invalid data passes silently

Example

# ❌ Before (arbitrary types without validators)
from pydantic import BaseModel

class MyModel(BaseModel):
    class Config:
        arbitrary_types_allowed = True

    db_connection: Connection  # No validation!

# ✅ After (with custom validator)
from pydantic import BaseModel, validator

class MyModel(BaseModel):
    class Config:
        arbitrary_types_allowed = True

    db_connection: Connection

    @validator('db_connection')
    def validate_connection(cls, v):
        if not v.is_connected:
            raise ValueError('Connection must be active')
        return v

What Unfault Detects

• arbitrary_types_allowed without validators
• Complex types without serialization logic
• Missing get_validators implementations

Related Rules

• python.pydantic.missing_validators