Kotlin Programming Language
Welcome to Kotlin!
Kotlin is a concise multiplatform language developed by JetBrains and contributors.
Some handy links:
Kotlin Multiplatform capabilities
Support for multiplatform programming is one of Kotlin’s key benefits. It reduces time spent writing and maintaining the same code for different platforms while retaining the flexibility and benefits of native programming.
Editing Kotlin
Build environment requirements
This repository is using Gradle toolchains feature
to select and auto-provision required JDKs from Eclipse Adoptium project.
Alternatively, it is still possible to only provide required JDKs via environment variables
(see gradle.properties for supported variable names). To ensure Gradle uses only JDKs
from environmental variables - disable Gradle toolchain auto-detection by passing -Porg.gradle.java.installations.auto-detect=false option
(or put it into $GRADLE_USER_HOME/gradle.properties).
On Windows you might need to add long paths setting to the repo:
git config core.longpaths true
Building
The project is built with Gradle. Run Gradle to build the project and to run the tests
using the following command on Unix/macOS:
./gradlew <tasks-and-options>
or the following command on Windows:
gradlew <tasks-and-options>
On the first project configuration gradle will download and setup the dependencies on:
intellij-core is a part of command line compiler and contains only necessary APIs.idea-full is a full blown IntelliJ IDEA Community Edition to be used in the plugin module.
These dependencies are quite large, so depending on the quality of your internet connection
you might face timeouts getting them. In this case, you can increase timeout by specifying the following
command line parameters on the first run:
./gradlew -Dhttp.socketTimeout=60000 -Dhttp.connectionTimeout=60000
Important gradle tasks
clean - clean build resultsdist - assembles the compiler distribution into dist/kotlinc/ folderinstall - build and install all public artifacts into local maven repositorycoreLibsTest - build and run stdlib, reflect and kotlin-test testsgradlePluginTest - build and run gradle plugin testscompilerTest - build and run all compiler tests
To reproduce TeamCity build use -Pteamcity=true flag. Local builds don't run proguard and have jar compression disabled by default.
OPTIONAL: Some artifacts, mainly Maven plugin ones, are built separately with Maven.
Refer to libraries/ReadMe.md for details.
To build Kotlin/Native, see
kotlin-native/README.md.
Working with the project in IntelliJ IDEA
It is recommended to use the latest released version of Intellij IDEA (Community or Ultimate Edition). You can download IntelliJ IDEA here.
After cloning the project, import the project in IntelliJ by choosing the project directory in the Open project dialog.
For handy work with compiler tests it's recommended to use Kotlin Compiler Test Helper.
Dependency verification
We have a dependencies verification feature enabled in the
repository for all Gradle builds. Gradle will check hashes (md5 and sha256) of used dependencies and will fail builds with
Dependency verification failed errors when local artifacts are absent or have different hashes listed in the
verification-metadata.xml file.
It's expected that verification-metadata.xml should only be updated with the commits that modify the build. There are some tips how
to perform such updates:
- Delete
components section of verification-metadata.xml to avoid stockpiling of old unused dependencies. You may use the following command:
#macOS
sed -i '' -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
#Linux & Git for Windows
sed -i -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
- Re-generate dependencies with Gradle's
--write-verification-metadata command (verify update relates to your changes)
./gradlew --write-verification-metadata sha256 -Pkotlin.native.enabled=true resolveDependencies
resolveDependencies task resolves dependencies for all platforms including dependencies downloaded by plugins.
You can also use ./scripts/update-verification-metadata.sh script which includes both of these steps
Keep in mind:
- If you’re adding a dependency with OS mentioned in an artifact name (
darwin, mac, osx, linux, windows), remember to add them to
implicitDependencies configuration or update resolveDependencies task if needed. resolveDependencies should resolve all dependencies
including dependencies for different platforms.
- If you have a
local.properties file in your Kotlin project folder, make sure that it doesn't contain kotlin.native.enabled=false.
Otherwise, native-only dependencies may not be added to the verification metadata. This is because local.properties has higher
precedence than the -Pkotlin.native.enabled=true specified in the Gradle command.
Updating a dependency
- Bump the version in libs.versions.toml.
- Update
verification-metadata.xml as described in Dependency verification.
- Build and publish all artifacts the same way TeamCity does:
./gradlew clean install publish mvnPublish dist -Pteamcity=true
- Check the published Maven and Gradle metadata and the compiler distribution contents with the artifacts tests:
./gradlew :repo:artifacts-tests:test
Using -dev versions
We publish -dev versions frequently.
For -dev versions you can use the list of available versions and include this maven repository:
maven("https://redirector.kotlinlang.org/maven/bootstrap")
License
Kotlin is distributed under the terms of the Apache License (Version 2.0). See license folder for details.
Contributing
Please be sure to review Kotlin's contributing guidelines to learn how to help the project.
Kotlin Foundation
The Kotlin Foundation is a non-profit organization whose mission is to promote and advance the Kotlin ecosystem. You can learn more about the structure and goals of the Kotlin Foundation on its official website.
