Kotlin SDK

RBS provides first-class Kotlin support with automatic Kotlin compiler and JDK management, Maven-compatible dependency resolution, JUnit 5 auto-inclusion, Spring Boot support, and linting.

Setup

Toolchain

load("@rbs//java/toolchain.rbs", "java_toolchain", "java_test_deps")
load("@rbs//kotlin/toolchain.rbs", "kotlin_toolchain")

# JDK (Kotlin requires JVM)
java_toolchain(name = "java", version = "17.0.11")

# Kotlin compiler
kotlin_toolchain(name = "kotlin", version = "2.0.21")

# JUnit 5 for tests
java_test_deps()

Dependencies

Define external packages using kotlin_repository. Uses the same Maven coordinate format as Java.

load("@rbs//kotlin/dependencies.rbs", "kotlin_repository")

kotlin_repository(
    name = "spring_boot_web",
    package = "org.springframework.boot:spring-boot-starter-web",
    version = "3.2.2",
)

kotlin_repository(
    name = "kotlinx_coroutines",
    package = "org.jetbrains.kotlinx:kotlinx-coroutines-core",
    version = "1.8.1",
)

Rules

`kotlin_library`

Creates a reusable Kotlin library (JAR).

load("@rbs//kotlin/rules.rbs", "kotlin_library")

kotlin_library(
    name = "greeter",
    srcs = ["Greeter.kt"],
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Kotlin source files.
`deps`	list	Dependencies (local or `@external://`).
`runtime_deps`	list	Runtime-only dependencies (not for compilation).
`resources`	list	Resource files to include in the JAR.

`kotlin_binary`

Creates an executable Kotlin application.

load("@rbs//kotlin/rules.rbs", "kotlin_binary")

kotlin_binary(
    name = "hello",
    srcs = ["Main.kt"],
    deps = [":greeter"],
    main = "MainKt",
)

# With external dependencies (coroutines)
kotlin_binary(
    name = "async_hello",
    srcs = ["AsyncMain.kt"],
    deps = [
        ":greeter",
        "@external://org_jetbrains_kotlinx_kotlinx-coroutines-core:1.8.1",
    ],
    main = "AsyncMainKt",
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Kotlin source files.
`main`	string	Fully qualified main class (required).
`deps`	list	Dependencies.
`runtime_deps`	list	Runtime-only dependencies.
`resources`	list	Resource files.
`javaopts`	list	JVM options.

`kotlin_test`

Runs Kotlin tests. JUnit 5 is automatically included.

load("@rbs//kotlin/rules.rbs", "kotlin_test")

kotlin_test(
    name = "greeting_service_test",
    srcs = [
        "src/main/kotlin/com/example/GreetingService.kt",
        "src/test/kotlin/com/example/GreetingServiceTest.kt",
    ],
    args = ["--select-class=com.example.GreetingServiceTest"],
)

`kotlin_lint` / `kt_lint`

Runs linting on Kotlin source files (supports ktlint).

load("@rbs//kotlin/lint.rbs", "kt_lint")

kt_lint(
    name = "lint",
    srcs = ["Main.kt", "Greeter.kt", "AsyncMain.kt"],
    ktlint = True,
)

Example: Kotlin Spring Boot

WORKSPACE.rbs
BUILD.rbs
Commands

load("@rbs//java/toolchain.rbs", "java_toolchain", "java_test_deps")
load("@rbs//kotlin/toolchain.rbs", "kotlin_toolchain")
load("@rbs//kotlin/dependencies.rbs", "kotlin_repository")

java_toolchain(name = "java", version = "17.0.11")
kotlin_toolchain(name = "kotlin", version = "2.0.21")
java_test_deps()

kotlin_repository(
    name = "spring_boot_web",
    package = "org.springframework.boot:spring-boot-starter-web",
    version = "3.2.2",
)

load("@rbs//kotlin/rules.rbs", "kotlin_binary", "kotlin_library", "kotlin_test", "kotlin_lint")
load("@rbs//oci/rules.rbs", "oci_image")

kotlin_library(
    name = "springboot_lib",
    srcs = glob(["src/main/kotlin/**/*.kt"]),
    deps = ["@external://org_springframework_boot_spring_boot_starter_web:3.2.2"],
)

kotlin_binary(
    name = "app",
    srcs = glob(["src/main/kotlin/**/*.kt"]),
    main = "com.example.springboot.ApplicationKt",
    resources = ["src/main/resources/application.properties"],
    deps = ["@external://org_springframework_boot_spring_boot_starter_web:3.2.2"],
    javaopts = ["-Djava.awt.headless=true"],
)

kotlin_test(
    name = "greeting_service_test",
    srcs = [
        "src/main/kotlin/com/example/springboot/GreetingService.kt",
        "src/test/kotlin/com/example/springboot/GreetingServiceTest.kt",
    ],
    deps = ["@external://org_springframework_boot_spring_boot_starter_web:3.2.2"],
    args = ["--select-class=com.example.springboot.GreetingServiceTest"],
)

kotlin_lint(
    name = "app_lint",
    srcs = glob(["src/main/kotlin/**/*.kt"]),
)

oci_image(
    name = "image",
    binary = ":app",
    base = "ubuntu:22.04",
    env = {"JAVA_OPTS": "-Djava.awt.headless=true"},
    tag = "kotlin-springboot-example:latest",
)

rbs build app                       # Build the application
rbs run app                         # Run Spring Boot server
rbs test greeting_service_test      # Run tests
rbs build app_lint                  # Lint code
rbs build image                     # Build container image

​Kotlin SDK

​Setup

​Toolchain

​Dependencies

​Rules

​kotlin_library

​kotlin_binary

​kotlin_test

​kotlin_lint / kt_lint

​Example: Kotlin Spring Boot