Kotlin Multiplatform Gradle DSL Reference
Multiplatform projects are in Alpha. Language features and tooling may change in future Kotlin versions.
The Kotlin Multiplatform Gradle plugin is a tool for creating Kotlin multiplatform projects. Here we provide a reference of its contents; use it as a reminder when writing Gradle build scripts for Kotlin multiplatform projects. Learn the concepts of Kotlin multiplatform projects, how to create and configure them.
Table of Contents
Id and version
The fully qualified name of the Kotlin Multiplatform Gradle plugin is org.jetbrains.kotlin.multiplatform
. If you use the Kotlin Gradle DSL, you can apply the plugin with kotlin(“multiplatform”)
. The plugin versions match the Kotlin release versions. The most recent version is 1.4.21.
plugins {
id 'org.jetbrains.kotlin.multiplatform' version '1.4.21'
}
plugins {
kotlin("multiplatform") version "1.4.21"
}
Top-level blocks
kotlin
is the top-level block for multiplatform project configuration in the Gradle build script. Inside kotlin
, you can write the following blocks:
Block | Description |
---|---|
<targetName> | Declares a particular target of a project. The names of available targets are listed in the Targets section. |
targets | All targets of the project. |
presets | All predefined targets. Use this for configuring multiple predefined targets at once. |
sourceSets | Configures predefined and declares custom source sets of the project. |
Targets
Target is a part of the build responsible for compiling, testing, and packaging a piece of software aimed for one of the supported platforms.
Each target can have one or more compilations. In addition to default compilations for test and production purposes, you can create custom compilations.
The targets of a multiplatform project are described in the corresponding blocks inside kotlin
, for example, jvm
, android
, iosArm64
. The complete list of available targets is the following:
Name | Description |
---|---|
jvm | Java Virtual Machine |
js | JavaScript |
android | Android (APK) |
androidNativeArm32 | Android NDK on ARM (ARM32) platforms |
androidNativeArm64 | Android NDK on ARM64 platforms |
androidNativeX86 | Android NDK on x86 platforms |
androidNativeX64 | Android NDK on x86_64 platforms |
iosArm32 | Apple iOS on ARM (ARM32) platforms (Apple iPhone 5 and earlier) |
iosArm64 | Apple iOS on ARM64 platforms (Apple iPhone 5s and newer) |
iosX64 | Apple iOS 64-bit simulator |
watchosArm32 | Apple watchOS on ARM (ARM32) platforms (Apple Watch Series 3 and earlier) |
watchosArm64 | Apple watchOS on ARM64_32 platforms (Apple Watch Series 4 and newer) |
watchosX86 | Apple watchOS simulator |
tvosArm64 | Apple tvOS on ARM64 platforms (Apple TV 4th generation and newer) |
tvosX64 | Apple tvOS simulator |
linuxArm64 | Linux on ARM64 platforms, for example, Raspberry Pi |
linuxArm32Hfp | Linux on hard-float ARM (ARM32) platforms |
linuxMips32 | Linux on MIPS platforms |
linuxMipsel32 | Linux on little-endian MIPS (mipsel) platforms |
linuxX64 | Linux on x86_64 platforms |
macosX64 | Apple macOS |
mingwX64 | 64-bit Microsoft Windows |
mingwX86 | 32-bit Microsoft Windows |
wasm32 | WebAssembly |
kotlin {
jvm()
iosX64()
macosX64()
js().browser()
}
Configuration of a target can include two parts:
- Common configuration available for all targets.
- Target-specific configuration.
Each target can have one or more compilations.
Common target configuration
In any target block, you can use the following declarations:
Name | Description |
---|---|
attributes | Attributes used for disambiguating targets for a single platform. |
preset | The preset that the target has been created from, if any. |
platformType | Designates the Kotlin platform of this target. Avaiable values: jvm , androidJvm , js , native , common . |
artifactsTaskName | The name of the task that builds the resulting artifacts of this target. |
components | The components used to setup Gradle publications. |
JVM targets
In addition to common target configuration, jvm
targets have a specific function:
Name | Description |
---|---|
withJava() | Includes Java sources into the JVM target’s compilations. |
Use this function for projects that contain both Java and Kotlin source files. Note that the default source directories for Java sources don’t follow the Java plugin’s defaults. Instead, they are derived from the Kotlin source sets. For example, if the JVM target has the default name jvm
, the paths are src/jvmMain/java
(for production Java sources) and src/jvmTest/java
for test Java sources. Learn how to include Java sources in JVM compilations.
kotlin {
jvm {
withJava()
}
}
JavaScript targets
The js
block describes the configuration of JavaScript targets. It can contain one of two blocks depending on the target execution environment:
Name | Description |
---|---|
browser | Configuration of the browser target. |
nodejs | Configuration of the Node.js target. |
Learn more about configuring Kotlin/JS projects.
Browser
browser
can contain the following configuration blocks:
Name | Description |
---|---|
testRuns | Configuration of test execution. |
runTask | Configuration of project running. |
webpackTask | Configuration of project bundling with Webpack. |
dceTask | Configuration of Dead Code Elimination. |
distribution | Path to output files. |
kotlin {
js().browser {
webpackTask { /* ... */ }
testRuns { /* ... */ }
dceTask {
keep("myKotlinJsApplication.org.example.keepFromDce")
}
distribution {
directory = File("$projectDir/customdir/")
}
}
}
Node.js
nodejs
can contain configurations of test and run tasks:
Name | Description |
---|---|
testRuns | Configuration of test execution. |
runTask | Configuration of project running. |
kotlin {
js().nodejs {
runTask { /* ... */ }
testRuns { /* ... */ }
}
}
Native targets
For native targets, the following specific blocks are available:
Name | Description |
---|---|
binaries | Configuration of binaries to produce. |
cinterops | Configuration of interop with C libraries. |
Binaries
There are the following kinds of binaries:
Name | Description |
---|---|
executable | Product executable. |
test | Test executable. |
sharedLib | Shared library. |
staticLib | Static library. |
framework | Objective-C framework. |
kotlin {
linuxX64 { // Use your target instead.
binaries {
executable {
// Binary configuration.
}
}
}
}
For binaries configuration, the following parameters are available:
Name | Description |
---|---|
compilation | The compilation from which the binary is built. By default, test binaries are based on the test compilation while other binaries - on the main compilation. |
linkerOpts | Options passed to a system linker during binary building. |
baseName | Custom base name for the output file. The final file name will be formed by adding system-dependent prefix and postfix to this base name. |
entryPoint | The entry point function for executable binaries. By default, it’s main() in the root package. |
outputFile | Access to the output file. |
linkTask | Access to the link task. |
runTask | Access to the run task for executable binaries. For targets other than linuxX64 , macosX64 , or mingwX64 the value is null . |
isStatic | For Objective-C frameworks. Includes a static library instead of a dynamic one. |
binaries {
executable('my_executable', [RELEASE]) {
// Build a binary on the basis of the test compilation.
compilation = compilations.test
// Custom command line options for the linker.
linkerOpts = ['-L/lib/search/path', '-L/another/search/path', '-lmylib']
// Base name for the output file.
baseName = 'foo'
// Custom entry point function.
entryPoint = 'org.example.main'
// Accessing the output file.
println("Executable path: ${outputFile.absolutePath}")
// Accessing the link task.
linkTask.dependsOn(additionalPreprocessingTask)
// Accessing the run task.
// Note that the runTask is null for non-host platforms.
runTask?.dependsOn(prepareForRun)
}
framework('my_framework' [RELEASE]) {
// Include a static library instead of a dynamic one into the framework.
isStatic = true
}
}
binaries {
executable("my_executable", listOf(RELEASE)) {
// Build a binary on the basis of the test compilation.
compilation = compilations["test"]
// Custom command line options for the linker.
linkerOpts = mutableListOf("-L/lib/search/path", "-L/another/search/path", "-lmylib")
// Base name for the output file.
baseName = "foo"
// Custom entry point function.
entryPoint = "org.example.main"
// Accessing the output file.
println("Executable path: ${outputFile.absolutePath}")
// Accessing the link task.
linkTask.dependsOn(additionalPreprocessingTask)
// Accessing the run task.
// Note that the runTask is null for non-host platforms.
runTask?.dependsOn(prepareForRun)
}
framework("my_framework" listOf(RELEASE)) {
// Include a static library instead of a dynamic one into the framework.
isStatic = true
}
}
Learn more about building native binaries.
CInterops
cinterops
is a collection of descriptions for interop with native libraries. To provide an interop with a library, add an entry to cinterops
and define its parameters:
Name | Description |
---|---|
defFile | def file describing the native API. |
packageName | Package prefix for the generated Kotlin API. |
compilerOpts | Options to pass to the compiler by the cinterop tool. |
includeDirs | Directories to look for headers. |
Learn more how to configure interop with native languages.
kotlin {
linuxX64 { // Replace with a target you need.
compilations.main {
cinterops {
myInterop {
// Def-file describing the native API.
// The default path is src/nativeInterop/cinterop/<interop-name>.def
defFile project.file("def-file.def")
// Package to place the Kotlin API generated.
packageName 'org.sample'
// Options to be passed to compiler by cinterop tool.
compilerOpts '-Ipath/to/headers'
// Directories for header search (an analogue of the -I<path> compiler option).
includeDirs.allHeaders("path1", "path2")
// A shortcut for includeDirs.allHeaders.
includeDirs("include/directory", "another/directory")
}
anotherInterop { /* ... */ }
}
}
}
}
kotlin {
linuxX64 { // Replace with a target you need.
compilations.getByName("main") {
val myInterop by cinterops.creating {
// Def-file describing the native API.
// The default path is src/nativeInterop/cinterop/<interop-name>.def
defFile(project.file("def-file.def"))
// Package to place the Kotlin API generated.
packageName("org.sample")
// Options to be passed to compiler by cinterop tool.
compilerOpts("-Ipath/to/headers")
// Directories for header search (an analogue of the -I<path> compiler option).
includeDirs.allHeaders("path1", "path2")
// A shortcut for includeDirs.allHeaders.
includeDirs("include/directory", "another/directory")
}
val anotherInterop by cinterops.creating { /* ... */ }
}
}
}
Android targets
The Kotlin multiplatform plugin contains two specific functions for android targets. Two functions help you configure build variants:
Name | Description |
---|---|
publishLibraryVariants() | Specifies build variants to publish. Learn more about publishing Android libraries. |
publishAllLibraryVariants() | Publishes all build variants. |
kotlin {
android {
publishLibraryVariants("release", "debug")
}
}
Learn more about compilation for Android.
The
android
configuration insidekotlin
doesn’t replace the build configuration of any Android project. Learn more about writing build scripts for Android projects in Android developer documentation.
Source sets
The sourceSets
block describes source sets of the project. A source set contains Kotlin source files that participate in compilations together, along with their resources, dependencies, and language settings.
A multiplatform project contains predefined source sets for its targets; developers can also create custom source sets for their needs.
Predefined source sets
Predefined source sets are set up automatically upon creation of a multiplatform project. Available predefined source sets are the following:
Name | Description |
---|---|
commonMain | Code and resources shared between all platforms. Available in all multiplatform projects. Used in all main compilations of a project. |
commonTest | Test code and resources shared between all platforms. Available in all multiplatform projects. Used in all test compilations of a project. |
<targetName><compilationName> | Target-specific sources for a compilation. <targetName> is the name of a predefined target and <compilationName> is the name of a compilation for this target. Examples: jsTest , jvmMain . |
With Kotlin Gradle DSL, the sections of predefined source sets should be marked by getting
.
kotlin {
sourceSets {
commonMain { /* ... */ }
}
}
kotlin {
sourceSets {
val commonMain by getting { /* ... */ }
}
}
Learn more about source sets.
Custom source sets
Custom source sets are created by the project developers manually. To create a custom source set, add a section with its name inside the sourceSets
section. If using Kotlin Gradle DSL, mark custom source sets by creating
.
kotlin {
sourceSets {
myMain { /* ... */ } // create or configure a source set by the name 'myMain'
}
}
kotlin {
sourceSets {
val myMain by creating { /* ... */ } // create a new source set by the name 'MyMain'
}
}
Note that a newly created source set isn’t connected to other ones. To use it in the project’s compilations, connect it with other source sets.
Source set parameters
Configurations of source sets are stored inside the corresponding blocks of sourceSets
. A source set has the following parameters:
Name | Description |
---|---|
kotlin.srcDir | Location of Kotlin source files inside the source set directory. |
resources.srcDir | Location of resources inside the source set directory. |
dependsOn | Connection with another source set. |
dependencies | Dependencies of the source set. |
languageSettings | Language settings applied to the source set. |
kotlin {
sourceSets {
commonMain {
kotlin.srcDir('src')
resources.srcDir('res')
dependencies {
/* ... */
}
}
}
}
kotlin {
sourceSets {
val commonMain by getting {
kotlin.srcDir("src")
resources.srcDir("res")
dependencies {
/* ... */
}
}
}
}
Compilations
A target can have one or more compilations, for example, for production or testing. There are predefined compilations that are added automatically upon target creation. You can additionally create custom compilations.
To refer to all or some particular compilations of a target, use the compilations
object collection. From compilations
, you can refer to a compilation by its name.
Learn more about configuring compilations.
Predefined compilations
Predefined compilations are created automatically for each target of a project except for Android targets. Available predefined compilations are the following:
Name | Description |
---|---|
main | Compilation for production sources. |
test | Compilation for tests. |
kotlin {
jvm {
compilations.main.output // get the main compilation output
compilations.test.runtimeDependencyFiles // get the test runtime classpath
}
}
kotlin {
jvm {
val main by compilations.getting {
output // get the main compilation output
}
compilations["test"].runtimeDependencyFiles // get the test runtime classpath
}
}
Custom compilations
In addition to predefined compilations, you can create your own custom compilations. To create a custom compilation, add a new item into the compilations
collection. If using Kotlin Gradle DSL, mark custom compilations by creating
.
Learn more about creating a custom compilation.
kotlin {
jvm() {
compilations.create('integrationTest') {
defaultSourceSet {
dependencies {
/* ... */
}
}
// Create a test task to run the tests produced by this compilation:
tasks.register('jvmIntegrationTest', Test) {
/* ... */
}
}
}
}
kotlin {
jvm() {
compilations {
val integrationTest by compilations.creating {
defaultSourceSet {
dependencies {
/* ... */
}
}
// Create a test task to run the tests produced by this compilation:
tasks.register<Test>("integrationTest") {
/* ... */
}
}
}
}
}
Compilation parameters
A compilation has the following parameters:
Name | Description |
---|---|
defaultSourceSet | The compilation’s default source set. |
kotlinSourceSets | Source sets participating in the compilation. |
allKotlinSourceSets | Source sets participating in the compilation and their connections via dependsOn() . |
kotlinOptions | Compiler options applied to the compilation. For the list of available options, see Compiler options. |
compileKotlinTask | Gradle task for compiling Kotlin sources. |
compileKotlinTaskName | Name of compileKotlinTask . |
compileAllTaskName | Name of the Gradle task for compiling all sources of a compilation. |
output | The compilation output. |
compileDependencyFiles | Compile-time dependency files (classpath) of the compilation. |
runtimeDependencyFiles | Runtime dependency files (classpath) of the compilation. |
kotlin {
jvm {
compilations.main.kotlinOptions {
// Setup the Kotlin compiler options for the 'main' compilation:
jvmTarget = "1.8"
}
compilations.main.compileKotlinTask // get the Kotlin task 'compileKotlinJvm'
compilations.main.output // get the main compilation output
compilations.test.runtimeDependencyFiles // get the test runtime classpath
}
// Configure all compilations of all targets:
targets.all {
compilations.all {
kotlinOptions {
allWarningsAsErrors = true
}
}
}
}
kotlin {
jvm {
val main by compilations.getting {
kotlinOptions {
// Setup the Kotlin compiler options for the 'main' compilation:
jvmTarget = "1.8"
}
compileKotlinTask // get the Kotlin task 'compileKotlinJvm'
output // get the main compilation output
}
compilations["test"].runtimeDependencyFiles // get the test runtime classpath
}
// Configure all compilations of all targets:
targets.all {
compilations.all {
kotlinOptions {
allWarningsAsErrors = true
}
}
}
}
Dependencies
The dependencies
block of the source set declaration contains the dependencies of this source set.
Learn more about configuring dependencies.
There are four types of dependencies:
Name | Description |
---|---|
api | Dependencies used in the API of the current module. |
implementation | Dependencies used in the module but not exposed outside it. |
compileOnly | Dependencies used only for compilation of the current module. |
runtimeOnly | Dependencies available at runtime but not visible during compilation of any module. |
kotlin {
sourceSets {
commonMain {
dependencies {
api 'com.example:foo-metadata:1.0'
}
}
jvm6Main {
dependencies {
implementation 'com.example:foo-jvm6:1.0'
}
}
}
}
kotlin {
sourceSets {
val commonMain by getting {
dependencies {
api("com.example:foo-metadata:1.0")
}
}
val jvm6Main by getting {
dependencies {
implementation("com.example:foo-jvm6:1.0")
}
}
}
}
Additionally, source sets can depend on each other and form a hierarchy. In this case, the dependsOn() relation is used.
Source set dependencies can also be declared in the top-level dependencies
block of the build script. In this case, their declarations follow the pattern <sourceSetName><DependencyKind>
, for example, commonMainApi
.
dependencies {
commonMainApi 'com.example:foo-common:1.0'
jvm6MainApi 'com.example:foo-jvm6:1.0'
}
dependencies {
"commonMainApi"("com.example:foo-common:1.0")
"jvm6MainApi"("com.example:foo-jvm6:1.0")
}
Language settings
The languageSettings
block of a source set defines certain aspects of project analysis and build. The following language settings are available:
Name | Description |
---|---|
languageVersion | Provides source compatibility with the specified version of Kotlin. |
apiVersion | Allows using declarations only from the specified version of Kotlin bundled libraries. |
enableLanguageFeature | Enables the specified language feature. The available values correspond to the language features that are currently experimental or have been introduced as such at some point. |
useExperimentalAnnotation | Allows using the specified opt-in annotation. |
progressiveMode | Enables the progressive mode. |
kotlin {
sourceSets.all {
languageSettings {
languageVersion = '1.4' // possible values: '1.0', '1.1', '1.2', '1.3', '1.4'
apiVersion = '1.4' // possible values: '1.0', '1.1', '1.2', '1.3', '1.4'
enableLanguageFeature('InlineClasses') // language feature name
useExperimentalAnnotation('kotlin.ExperimentalUnsignedTypes') // annotation FQ-name
progressiveMode = true // false by default
}
}
}
kotlin {
sourceSets.all {
languageSettings.apply {
languageVersion = "1.4" // possible values: "1.0", "1.1", "1.2", "1.3", "1.4"
apiVersion = "1.4" // possible values: "1.0", "1.1", "1.2", "1.3", "1.4"
enableLanguageFeature("InlineClasses") // language feature name
useExperimentalAnnotation("kotlin.ExperimentalUnsignedTypes") // annotation FQ-name
progressiveMode = true // false by default
}
}
}