Valdi is a modular Kotlin library designed for validation and domain-driven design (DDD) enforcement in your Kotlin projects. It provides a powerful validation DSL, domain modeling annotations, and static analysis tooling to help you build robust, maintainable applications aligned with DDD principles.

valdi-validation-core provides a Kotlin-first validation framework centered around the concept of a Factory. A factory validates input using a set of constraints and either produces a valid output or returns validation errors.

Constraints are defined as predicates coupled with error results implementing a marker interface for validation failures. Validation stops at the first failure, providing clear and precise error feedback.

The API exposes a simple and expressive DSL to build constraints inline, supporting both constant and lazily created errors.

val factory = factory<UserInput, User, UserError> {
    constraints {
        gives(UserError.EmptyName) on { it.name.isBlank() }
        gives { UserError.InvalidEmail(it.email) } unless { it.email.isValidEmail() }
    }
    constructor { input -> User(input.name, input.email) }
}

sealed interface UserError : ValidationError { /* ... */ }

val result: ValidationResult<User, UserError> = factory.create(input)
val unsafe: User = factory.createOrThrow(input)
val nullable: User? = factory.createOrNull(input)

To support Domain-Driven Design practices, valdi provides optional modules that integrate with your domain model and help enforce consistency:

The valdi-domain-core module introduces marker annotations like @ValueObject, @AggregateRoot, and @DomainEntity. These are used to declare the role of a class within your domain model. They do not affect behavior but serve as structural metadata.

The valdi-domain-detekt module provides Detekt rules that analyze your codebase for violations of common DDD patterns, based on the annotations defined in valdi-domain-core. This enables early feedback during development and helps maintain architectural boundaries.

These modules are optional and can be used independently of the validation system.

valdi is published as a set of modular libraries. You can include only what you need.

implementation("com.y9vad9.valdi:valdi-validation-core:$version")

implementation("com.y9vad9.valdi:valdi-validation-core:$version")

detektPlugins("com.y9vad9.valdi:valdi-domain-detekt:$version")

valdi is a Kotlin Multiplatform library with support for the following targets:

• JVM (with toolchain targeting Java 11)
• JavaScript (both Browser and Node.js)
• iOS (x64, arm64, simulator arm64)
• WebAssembly:
• wasmJs (for both Browser and Node.js)
• wasmWasi (for Node.js)

This project is licensed under the MIT License. You are free to use, modify, and distribute it with attribution.