KDraft

A Kotlin KSP (Kotlin Symbol Processing) annotation processor for automatic Draft DSL Builder code generation.

Features

• @Draftable Annotation: Mark data classes to automatically generate Draft builders
• DSL-style Builders: Fluent, type-safe builder pattern using Kotlin DSL syntax
• Dynamic Property Setting: Set properties by name using the set(propertyName, value) method
• Type Safety: Generated code maintains full type safety

Usage

1. Add Dependencies

In your build.gradle.kts:

plugins {
    kotlin("jvm") version "2.3.0"
    id("com.google.devtools.ksp") version "2.3.4"
}

dependencies {
    implementation("com.bangbang93.kdraft:kdraft-annotations:1.0.0")
    ksp("com.bangbang93.kdraft:kdraft-processor:1.0.0")
}

2. Annotate Your Data Class

@Draftable
data class User(
    val id: Int,
    val name: String,
    val email: String,
    val age: Int
)

3. Use the Generated DSL

val user = userDraft {
    id = 1
    name = "John Doe"
    email = "somebody@example.com"
    set("age", 30)
}

Generated Code

For the User class above, the processor generates:

class UserDraft {
    var id: Int = 0
    var name: String = ""
    var email: String = ""
    var age: Int = 0

    fun set(propertyName: String, value: Any?) {
        when (propertyName) {
            "id" -> id = value as Int
            "name" -> name = value as String
            "email" -> email = value as String
            "age" -> age = value as Int
            else -> throw IllegalArgumentException("Unknown property: $propertyName")
        }
    }

    fun build(): User = User(id, name, email, age)
}

fun userDraft(block: UserDraft.() -> Unit): User {
    return UserDraft().apply(block).build()
}

Building

./gradlew build

Running the Sample

./gradlew :kdraft-sample:run

How It Works

1. Annotate a data class with @Draftable
2. KSP processor scans for annotated classes during compilation
3. For each annotated class, it generates:
   • A Draft class with mutable properties
   • A DSL function for convenient instance construction
   • A set() method for dynamic property assignment
4. Generated code is placed in build/generated/ksp/main/kotlin/

Type Support

The processor supports the following types with default values:

Type	Default Value
Int	0
Long	0L
Short	0
Byte	0
Float	0.0f
Double	0.0
Boolean	false
Char	'\u0000'
String	""
List	emptyList()
Set	emptySet()
Map	emptyMap()
Nullable types	null

License

MIT License