Kotlin Language Server

The extension provides IntelliJ-powered features for Kotlin development, including:

• Code Intelligence: Up-to-date Kotlin language support, code completion, signature help, diagnostics, inspections, and quick fixes for Kotlin and kotlinx libraries.
• Navigation: Go to definition, references, type definition, implementation, call hierarchy, and documentation hover support.
• Refactoring & Editing: Rename refactoring, organize imports, code formatting, code folding, and file templates for new Kotlin files.
• Visual Aids: Semantic highlighting, inlay hints for types and parameter names, and document/workspace symbols.
• Build Systems: Support for JVM projects using Gradle, Maven, and experimental Android Gradle Plugin support. (Note: Kotlin Multiplatform (KMP) support is planned for future releases).

The Kotlin Language Server provides the following features based on IntelliJ IDEA implementation:

• Language Support: Up-to-date Kotlin language versions and semantic highlighting.
• IntelliJ-powered Intelligence: Code completion, diagnostics, and quick fixes for Kotlin and kotlinx libraries.
• Refactoring & Editing: Rename refactoring, organize imports, code formatting, and code folding.
• Navigation: Documentation navigation, hover support, and Call Hierarchy.
• Build Systems: Support for JVM projects using Gradle and Maven. Experimental support for the Android Gradle Plugin is available. (Note: Kotlin Multiplatform (KMP) support is planned for future releases).

To set up the development environment, install dependencies using pnpm install. To run the extension in a development host, open the project in VS Code and press F5 (selecting the Extension launch configuration). This triggers a watch task.

When making changes to files in src/, Rspack will rebuild automatically. To apply changes in the development host after a rebuild, use Cmd+R (or Ctrl+R on Windows/Linux) to reload the window.

If you need to rebuild the tree-sitter-kotlin.wasm artifact after updating the source, follow these steps:

1. Check out the desired commit from the tree-sitter-kotlin source repository.
2. Run the tree-sitter build command using the --wasm flag, pointing to the path of the checked-out source.
3. This process requires Docker with the emscripten/emsdk image.
4. Note that the package uses a pre-generated src/parser.c, so a tree-sitter generate step is not required.
5. Copy the resulting tree-sitter-kotlin.wasm file into the current directory and update the commit reference in the documentation.

tree-sitter build --wasm <path-to-tree-sitter-kotlin-source>

To use the Kotlin language server in Visual Studio Code, follow these steps:

1. Install the extension in Visual Studio Code.
2. Open a folder containing a Kotlin JVM project managed by Gradle or Maven.
3. Open any .kt file to activate the extension and the language server.

Important Migration Note: If you have an older extension named jetbrains.kotlin installed from GitHub, you must uninstall it when prompted by the dialog. The new jetbrains.kotlin-server extension will not activate correctly if the old extension is still present. After uninstalling, reload the VS Code window.

4. Wait for the project import and indexing process to complete before using features.

To build a VSIX package, ensure that server artifacts are built first, then execute the ./build.sh script.

If building this package within a pnpm workspace, you may need to enable pnpm 11 using corepack first:

./build.sh

# If in a pnpm workspace, enable pnpm 11:
corepack enable
corepack prepare pnpm@11.4.0 --activate

To connect Neovim to a kotlin-lsp instance already running and listening on a network port (default is 9999), configure nvim.lsp using vim.lsp.rpc.connect.

{
  cmd = vim.lsp.rpc.connect('127.0.0.1', tonumber(9999))
  single_file_support = true,
  filetypes = { "kotlin" },
  root_markers = { "build.gradle", "build.gradle.kts", "pom.xml" },
}

If you use the nvim-lspconfig plugin, you can use the built-in preset for kotlin_lsp. Ensure the kotlin-lsp CLI is installed and available in your $PATH before configuring.

-- enable the language server
vim.lsp.enable('kotlin_lsp')

-- configure language server's options
vim.lsp.config('kotlin_lsp', {
    single_file_support = false,
})

To run kotlin-lsp using the stdio communication method, follow these steps:

1. Install socat and netcat on your system.
2. Ensure the kotlin-lsp.sh script is executable: chmod +x $KOTLIN_LSP_DIR/kotlin-lsp.sh
3. Create a symlink to kotlin-lsp.sh in your $PATH (e.g., $HOME/.local/bin/kotlin-ls).
4. Configure nvim.lsp with the following settings:

{
  cmd = { "kotlin-ls", "--stdio" },
  single_file_support = true,
  filetypes = { "kotlin" },
  root_markers = { "build.gradle", "build.gradle.kts", "pom.xml" },
}

To use the Kotlin Language Server with the Helix editor, ensure the kotlin-lsp CLI is installed and available in your $PATH. Then, add the following configuration to your languages.toml file (typically located at ~/.config/helix/languages.toml):

[[language]]
name = "kotlin"
language-servers = [ "kotlin-lsp" ]