Validation engine

1. Setup

from tpy.validation import validate, ValidationException, Validator
from tpy.http import ApiResponse

No extra dependency. Use in controllers/services on incoming dict payloads.

2. Basic usage

try:
    data = validate(
        payload,
        {
            "email": "required|email",
            "age": "required|integer|min:18",
            "password": "required|confirmed",
            "role": "nullable|in:admin,user",
        },
    )
except ValidationException as exc:
    return ApiResponse.validation_error(exc)

# data is the cleaned/accepted input
return ApiResponse.success(service.create(data))

3. How it works

1. Rules are pipe-separated strings (required|email|min:3).
2. The engine runs each rule in order for every field.
3. On failure it raises ValidationException with per-field messages.
4. ApiResponse.validation_error(exc) turns that into HTTP 422 JSON.

4. Custom rules

Validator.extend(
    "odd",
    lambda attr, value, data: int(value) % 2 == 1,
    "Value must be odd.",
)
Validator.make({"n": 3}, {"n": "odd"}).validate()