ValidationError)¶

AutoCRUD supports custom validation on write operations (create/update/patch/modify), in addition to msgspec's own type-level validation.

Two layers of validation¶

A) Type-level validation (msgspec)¶

Happens when decoding / constructing your msgspec.Struct
Errors are typically msgspec.ValidationError

B) Domain/business validation (AutoCRUD)¶

Your custom rule checks (e.g. cross-field constraints, invariants)
Should raise autocrud.types.ValidationError (or ValueError, which AutoCRUD will wrap)

Validator forms accepted¶

Depending on where you attach it, AutoCRUD accepts validators in these forms:

1) Callable¶

A simple function:

def validate_user(u: User) -> None:
    if u.age < 0:
        raise ValueError("age must be >= 0")

2) `IValidator` implementation¶

from autocrud.types import IValidator

class PriceValidator(IValidator):
    def validate(self, data) -> None:
        if data.price < 0:
            raise ValueError("Price must be non-negative")

3) Pydantic model (bridge)¶

If you register a Pydantic BaseModel as the model type, AutoCRUD can use it as a validator (by converting it and validating through Pydantic), when no validator is provided elsewhere.

Where to attach validators¶

Attach via `add_model(...)`¶

crud.add_model(User, validator=validate_user)
# or
crud.add_model(User, validator=PriceValidator())

Attach via `Schema(...)`¶

schema = Schema(User, "v2", validator=validate_user).step("v1", migrate)
crud.add_model(schema)

Errors¶

`ValidationError`¶

AutoCRUD uses ValidationError (a ValueError subclass) for domain validation failures. This is intentionally distinct from msgspec.ValidationError.

Practical rule:

in validators, raise ValueError with a clear message
AutoCRUD will surface it as ValidationError (or pass through if already ValidationError)