Validation Classes¶

ValidationResult¶

@dataclass
class ValidationResult(Generic[T]):
    ok: bool
    errors: list[str]
    ctx: T

Result from .validate() on a validating combinator.

Methods:

raise_if_invalid(exc_type: type[Exception]) -> None -- Raise an exception if validation failed

Example:

result = can_trade.validate(user)
if not result.ok:
    print(result.errors)
    # ["User Bob must be an admin", "Account must be older than 30 days"]

result.raise_if_invalid(ValueError)

ValidatingCombinator¶

class ValidatingCombinator(Generic[T])

Base class for validating combinators. Supports &, |, and ~ operators.

Methods:

validate(ctx: T) -> ValidationResult[T] -- Run validation and collect all errors

ValidatingPredicate¶

class ValidatingPredicate(ValidatingCombinator[T])

Predicate with an error message. Created by @vrule and @vrule_args.

The error can be a format string (using {ctx} and parameter names) or a callable (ctx) -> str.

Example:

@vrule(error="User {ctx.name} must be an admin")
def is_admin(user):
    return user.is_admin

AsyncValidatingCombinator¶

class AsyncValidatingCombinator(Generic[T])

Async base class for validating combinators. Supports &, |, and ~ operators.

Methods:

async validate(ctx: T) -> ValidationResult[T] -- Run async validation

AsyncValidatingPredicate¶

class AsyncValidatingPredicate(AsyncValidatingCombinator[T])

Async predicate with an error message. Created by @async_vrule and @async_vrule_args.

Example:

@async_vrule(error="User must have permission")
async def has_permission(user):
    return await db.check_permission(user.id)