Configure compilations
Kotlin multiplatform projects use compilations for producing artifacts. Each target can have one or more compilations, for example, for production and test purposes.
For each target, default compilations include:
main
andtest
compilations for JVM, JS, and Native targets.- A compilation per Android build variant, for Android targets.
If you need to compile something other than production code and unit tests, for example, integration or performance tests, you can create a custom compilation.
You can configure how artifacts are produced in:
- All compilations in your project at once.
- Compilations for one target since one target can have multiple compilations.
- A specific compilation.
See the list of compilation parameters and compiler options available for all or specific targets.
Configure all compilations
kotlin {
targets.all {
compilations.all {
kotlinOptions {
allWarningsAsErrors = true
}
}
}
}
Configure compilations for one target
kotlin {
jvm().compilations.all {
kotlinOptions {
sourceMap = true
metaInfo = true
}
}
}
kotlin {
targets.jvm.compilations.all {
kotlinOptions {
sourceMap = true
metaInfo = true
}
}
}
Configure one compilation
kotlin {
jvm().compilations.main {
kotlinOptions {
jvmTarget = "1.8"
}
}
}
kotlin {
jvm {
val main by compilations.getting {
kotlinOptions {
jvmTarget = "1.8"
}
}
}
}
Create a custom compilation
If you need to compile something other than production code and unit tests, for example, integration or performance tests, create a custom compilation.
For example, to create a custom compilation for integration tests of the jvm()
target, add a new item to the compilations
collection.
For custom compilations, you need to set up all dependencies manually. The default source set of a custom compilation does not depend on the
commonMain
and thecommonTest
source sets.
kotlin {
jvm() {
compilations.create('integrationTest') {
defaultSourceSet {
dependencies {
def main = compilations.main
// Compile against the main compilation's compile classpath and outputs:
implementation(main.compileDependencyFiles + main.output.classesDirs)
implementation kotlin('test-junit')
/* ... */
}
}
// Create a test task to run the tests produced by this compilation:
tasks.register('jvmIntegrationTest', Test) {
// Run the tests with the classpath containing the compile dependencies (including 'main'),
// runtime dependencies, and the outputs of this compilation:
classpath = compileDependencyFiles + runtimeDependencyFiles + output.allOutputs
// Run only the tests from this compilation's outputs:
testClassesDirs = output.classesDirs
}
}
}
}
kotlin {
jvm() {
compilations {
val main by getting
val integrationTest by compilations.creating {
defaultSourceSet {
dependencies {
// Compile against the main compilation's compile classpath and outputs:
implementation(main.compileDependencyFiles + main.output.classesDirs)
implementation(kotlin("test-junit"))
/* ... */
}
}
// Create a test task to run the tests produced by this compilation:
tasks.register<Test>("integrationTest") {
// Run the tests with the classpath containing the compile dependencies (including 'main'),
// runtime dependencies, and the outputs of this compilation:
classpath = compileDependencyFiles + runtimeDependencyFiles + output.allOutputs
// Run only the tests from this compilation's outputs:
testClassesDirs = output.classesDirs
}
}
}
}
}
You also need to create a custom compilation in other cases, for example, if you want to combine compilations for different JVM versions in your final artifact, or you have already set up source sets in Gradle and want to migrate to a multiplatform project.
Include Java sources in JVM compilations
By default, the JVM target ignores Java sources and compiles only Kotlin source files.
To include Java sources in the compilations of the JVM target, explicitly enable the Java language support for the target:
In the build script of an existing project.
kotlin {
jvm {
withJava()
}
}
This applies the Gradle
java
plugin and configures the target to cooperate with it.
The Java source files are placed in the child directories of the Kotlin source roots. For example, the paths are:
The common source sets cannot include Java sources.
Due to current limitations, the Kotlin plugin replaces some tasks configured by the Java plugin:
- The target’s JAR task instead of
jar
(for example,jvmJar
). - The target’s test task instead of
test
(for example,jvmTest
). - The resources are processed by the equivalent tasks of the compilations instead of
*ProcessResources
tasks.
The publication of this target is handled by the Kotlin plugin and doesn’t require steps that are specific for the Java plugin.
Configure interop with native languages
Kotlin provides interoperability with native languages and DSL to configure this for a specific compilation.
Native language | Supported platforms | Comments |
---|---|---|
C | All platforms, except for WebAssembly | |
Objective-C | Apple platforms (macOS, iOS, watchOS, tvOS) | |
Swift via Objective-C | Apple platforms (macOS, iOS, watchOS, tvOS) | Kotlin can use only Swift declarations marked with the @objc attribute. |
A compilation can interact with several native libraries. Configure interoperability in the cinterops
block of the compilation with available parameters.
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 eqivalent of the -I<path> compiler option).
includeDirs.allHeaders("path1", "path2")
// Additional directories to search headers listed in the 'headerFilter' def-file option.
// -headerFilterAdditionalSearchPrefix command line option equivalent.
includeDirs.headerFilterOnly("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 to look for headers.
includeDirs.apply {
// Directories for header search (an equivalent of the -I<path> compiler option).
allHeaders("path1", "path2")
// Additional directories to search headers listed in the 'headerFilter' def-file option.
// -headerFilterAdditionalSearchPrefix command line option equivalent.
headerFilterOnly("path1", "path2")
}
// A shortcut for includeDirs.allHeaders.
includeDirs("include/directory", "another/directory")
}
val anotherInterop by cinterops.creating { /* ... */ }
}
}
}
Compilation for Android
The compilations created for an Android target by default are tied to Android build variants: for each build variant, a Kotlin compilation is created under the same name.
Then, for each Android source set compiled for each of the variants, a Kotlin source set is created under that source set name prepended by the target name, like the Kotlin source set androidDebug
for an Android source set debug
and the Kotlin target named android
. These Kotlin source sets are added to the variants’ compilations accordingly.
The default source set commonMain
is added to each production (application or library) variant’s compilation. The commonTest
source set is similarly added to the compilations of unit test and instrumented test variants.
Annotation processing with kapt
is also supported, but due to current limitations it requires that the Android target is created before the kapt
dependencies are configured, which needs to be done in a top-level dependencies
block rather than within Kotlin source set dependencies.
kotlin {
android { /* ... */ }
}
dependencies {
kapt("com.my.annotation:processor:1.0.0")
}
Compilation of the source set hierarchy
Kotlin can build a source set hierarchy with the dependsOn
relation.
If the source set jvmMain
depends on a source set commonMain
then:
- Whenever
jvmMain
is compiled for a certain target,commonMain
takes part in that compilation as well and is also compiled into the same target binary form, such as JVM class files. - Sources of
jvmMain
‘see’ the declarations ofcommonMain
, including internal declarations, and also see the dependencies ofcommonMain
, even those specified asimplementation
dependencies. jvmMain
can contain platform-specific implementations for the expected declarations ofcommonMain
.- The resources of
commonMain
are always processed and copied along with the resources ofjvmMain
. - The language settings of
jvmMain
andcommonMain
should be consistent.
Language settings are checked for consistency in the following ways:
jvmMain
should set alanguageVersion
that is greater than or equal to that ofcommonMain
.jvmMain
should enable all unstable language features thatcommonMain
enables (there’s no such requirement for bugfix features).jvmMain
should use all experimental annotations thatcommonMain
uses.apiVersion
, bugfix language features, andprogressiveMode
can be set arbitrarily.