@vytches/ddd-validation

Specification pattern, business rule validators, and validation error types

Installation

pnpm add @vytches/ddd-validation

What's included

Specification pattern

| Export | Kind | Description | | --------------------------------- | ----- | ------------------------------------------------------------------------------------------- | | Specification | class | Alias for CompositeSpecification — abstract base with and(), or(), not() | | CompositeSpecification<T> | class | Abstract specification with composition methods and PredicateSpecification static factory | | AsyncCompositeSpecification<T> | class | Async variant with andAsync(), orAsync(), notAsync() | | MemoizedSpecification<T> | class | Wraps another specification and caches the result | | NotSpecification<T> | class | Negates another specification | | AndSpecification<T> | class | Conjunction of two specifications | | OrSpecification<T> | class | Disjunction of two specifications | | AndAsyncSpecification<T> | class | Async conjunction | | OrAsyncSpecification<T> | class | Async disjunction | | NotAsyncSpecification<T> | class | Async negation | | AlwaysTrueSpecification<T> | class | Always returns true | | AlwaysFalseSpecification<T> | class | Always returns false | | PredicateSpecification<T> | class | Wraps a predicate function as a specification | | PropertyBetweenSpecification<T> | class | Checks that a property value is between two bounds | | PropertyInSpecification<T> | class | Checks that a property value is in an allowed set | | PropertyEqualsSpecification<T> | class | Checks that a property value equals an expected value | | SpecificationValidator<T> | class | Validates an object against a specification and returns errors |

Business rules

| Export | Kind | Description | | -------------------------- | ----- | ------------------------------------------------------------------- | | BusinessRuleValidator<T> | class | Fluent validator builder — chain must(), ensure(), validate() |

Validation errors

| Export | Kind | Description | | ------------------ | ----- | ------------------------------------------------------ | | ValidationError | class | Single validation error with property path and message | | ValidationErrors | class | Collection of ValidationError instances |

Facade

| Export | Kind | Description | | ------------------ | -------------------------------- | ------------------------------------------------------------------ | | ValidationFacade | object (aliased as Validation) | Factory methods: create<T>(), fromSpecification(), combine() |

Rules registry

| Export | Kind | Description | | --------------- | ----- | ---------------------------- | | RulesRegistry | class | Registry for named rule sets |

Adapters

| Export | Kind | Description | | ----------------------- | ----- | -------------------------------------------------------- | | BaseValidationAdapter | class | Base class for integrating external validation libraries | | AdapterUtils | class | Helper utilities for adapter implementations |

Quick start

Specification pattern

import { Specification } from '@vytches/ddd-validation';

class AgeAtLeast18 extends Specification<{ age: number }> {
  isSatisfiedBy(candidate: { age: number }): boolean {
    return candidate.age >= 18;
  }
}

class HasValidEmail extends Specification<{ email: string }> {
  isSatisfiedBy(candidate: { email: string }): boolean {
    return candidate.email.includes('@');
  }
}

const rule = new AgeAtLeast18().and(new HasValidEmail());
const isValid = rule.isSatisfiedBy({ age: 20, email: '[email protected]' }); // true

BusinessRuleValidator

import { BusinessRuleValidator } from '@vytches/ddd-validation';

interface CreateUser {
  name: string;
  email: string;
  age: number;
}

const validator = BusinessRuleValidator.create<CreateUser>()
  .must(u => u.name.length > 0, 'name', 'Name is required')
  .must(u => u.email.includes('@'), 'email', 'Invalid email')
  .must(u => u.age >= 18, 'age', 'Must be 18 or older');

const result = validator.validate({
  name: 'Alice',
  email: '[email protected]',
  age: 20,
});
if (!result.isSuccess) {
  console.error(result.error); // ValidationErrors
}

ValidationFacade

import { ValidationFacade as Validation } from '@vytches/ddd-validation';

const validator = Validation.fromSpecification(
  new AgeAtLeast18(),
  'Must be at least 18 years old',
  'age'
);

const result = validator.validate(user);

PredicateSpecification (inline)

import { CompositeSpecification } from '@vytches/ddd-validation';

const isActive = CompositeSpecification.create<User>(u => u.active === true);
const isAdmin = CompositeSpecification.create<User>(u => u.role === 'admin');

const isActiveAdmin = isActive.and(isAdmin);

Package boundaries

@vytches/ddd-validation depends on:

• @vytches/ddd-contracts — ISpecification, IAsyncSpecification, IValidator, IValidationErrors
• @vytches/ddd-utils — Result

License

MIT