The ReSharper Platform is based on .NET, implemented mostly in C#. In addition, Rider plugins run as a JVM application, mainly implemented in Java and Kotlin. At this time, it's not possible to develop plugins for the ReSharper Platform in non-.NET languages. Developing a plugin for the ReSharper Platform requires knowledge and experience with the following technologies and concepts:
Java/Kotlin, and other IntelliJ-relevant technologies, as described in the IntelliJ SDK documentation (Rider only)
Please keep in mind that the ReSharper Platform is a large project, and while we are doing our best to cover as many topics as possible, it is not possible to include every feature and use-case in the documentation. Developing a plugin will sometimes require digging into sample projects, analyzing other open-source plugins, or getting help on our tracked platforms.