Kotlin plugin

There are currently two Kotlin plugins.

JetBrains Kotlin plugin

Donated by JetBreains.

Original URL: https://github.com/JetBrains/kotlin-netbeans

It can be found inside contrib folder of Apache NetBeans source code:

https://github.com/JetBrains/kotlin-netbeans/issues/137

https://github.com/apache/netbeans/pull/1398

Steps to build it:

1. The pom.xml requires some dependencies that are not in the central maven repository. These are: asm-all.jar, idea-formatter.jar, intellij-core.jar, kotlin-converter.jar, kotlin-formatter.jar, kotlin-ide-common.jar, openapi-formatter.jar.  intellij-core.jar artifact can be directly taken from: https://www.jetbrains.com/intellij-repository/releases. The other artifacts can be found at https://github.com/JetBrains/kotlin-eclipse project inside the kotlin-bundled-compiler folder. Once you have collected all these libraries, create a lib folder inside kotlin-netbeans project and paste them inside there.
2. In NetBeans, click on Tools → Plugins → Settings tab and add a new plugin Portal: Name: NetBeans 8.2 Plugin Portal, URL: http://updates.netbeans.org/netbeans/updates/8.2/uc/final/distribution/catalog.xml.gz. Make it active.

Once you build the project, all Java and NetBeans dependencies should be resolved. However, not the Kotlin code which throws a lot of compilation errors. The plugin contains Kotlin code that needs to be built/migrated to the latest Kotlin compiler version and all the compilation errors need to be fixed.

LSP Kotlin Plugin

NetBeans 12.x and later already provide some basic support in the java/kotlin.editor module. This should be the plugin that should be further developed. It uses Kotlin.tmLanguage.json. This JavaDoc explains how to integrate a TextMate lexer with NetBeans.

With this plugin one can open a .kt file via the Windows→Favourites tab.

There are also contrib/groovy.grails and contrib/groovy.grailsproject.