JetBrains has shown off a pre-alpha version of its forthcoming official Kotlin support for Visual Studio Code and an implementation of Language Server Protocol for the Kotlin language. The announcements were made at JetBrains' KotlinConf, along with news of what's coming in Kotlin 2.2. 

Kotlin is the open source language originated by JetBrains and promoted by Google as a first class language for Android to replace or supplement Java.

JetBrains used the conference to show off a pre-alpha version of a new Kotlin extension for Visual Studio Code, along with an official Kotlin Language Server Protocol (LSP). Both are currently only accessible on GitHub.

The LSP is based on IntelliJ IDEA& and the IntelliJ IDEA Kotlin Plugin implementation. Microsoft's LSP defines a common protocol for language servers. LSPs enable IDEs to provide features such as auto completion, go to definition, and provide help from documentation and tips. The extension and LSP are necessary evils for JetBrains; they increase the attractiveness of VS Code, which is a rival to their own IDEs; but extend the options for developers wanting to use Kotlin so increase take-up of the JetBrains language. 

JetBrains says that although the extension is still in its early stages, it already includes basic support for code completion, navigation, inspections, quick-fixes, Java interoperability, and basic project import. The current version only supports Kotlin Gradle projects that are JVM-only. An Alpha release is planned for later this year. 

More details were also released at the conference on what's coming in Kotlin 2.2, which is described as "on the horizon"; in fact a release candidate was announced on May 15. The new features include the addition of guard conditions in when-with-subject; multi-dollar interpolation; non-local break and continue; and context parameters (currently in beta). 

Guard conditions were introduced in Kotlin 2.1, and can be used in when expressions or statements with subjects. Guard conditions allow you to include more than one condition for the branches of a when expression, making complex control flows more explicit and concise as well as flattening the code structure. Version 2.2 extends this to work with when with subjects. 

The new version also adds a preview of context parameters. These allow functions and properties to declare dependencies that are implicitly available in the surrounding context. This feature replaces an older experimental feature called context receivers.

Other announcements at the conference include the move to K2 mode as the default in IntelliJ IDEA 2025.1, meaning that the IDE now reuses parts of the much faster K2 compiler for code analysis; and further work on Amper, JetBrains' experimental Kotlin and JVM build tool.

JetBrains also announced an open source framework called Koog, which is designed for building AI agents in Kotlin. Koog includes predefined workflows and patterns, which you can use directly or combine with each other. 

• Mike James is the author of Programmer’s Guide To Kotlin, 3rd Ed written for Java programmers, Android developers and programmers wanting to discover why Kotlin is a better Java and of Android Programming in Kotlin: Starting With An App.

More Information

Kotlin Home Page

Kotlin LSP On GitHub

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