vscode-ktfmt

Format Kotlin code in Visual Studio Code with ktfmt (currently bundled version: 0.62).

Features

Document formatting provider for .kt and .kts files (works with Format Document and editor.formatOnSave).
Explicit Kotlin: Format with ktfmt command.
Automatically downloads the supported ktfmt fat JAR on first use, with SHA-256 verification.
Configurable formatting style: meta, google, kotlinlang (default).
Override hooks for both the Java installation (ktfmt.javaHome) and the ktfmt JAR (ktfmt.jarPath).

Requirements

A Java Development Kit (JDK 11+ recommended) reachable via one of:
1. ktfmt.javaHome setting
2. JAVA_HOME environment variable (works out of the box with SDKMAN!)
3. java on PATH

Installation

Install from the Visual Studio Code Marketplace (publisher: ombratteng).

Usage

Open any .kt or .kts file and:

Run Format Document (default Shift+Alt+F), or
Run the Kotlin: Format with ktfmt command from the Command Palette, or

Enable editor.formatOnSave and set the default formatter:

{
  "[kotlin]": {
    "editor.defaultFormatter": "ombratteng.ktfmt",
    "editor.formatOnSave": true
  },
  "[kotlin-script]": {
    "editor.defaultFormatter": "ombratteng.ktfmt",
    "editor.formatOnSave": true
  }
}

Settings

Setting	Type	Default	Description
`ktfmt.style`	enum	`"meta"`	Formatting style: `meta`, `google`, `kotlinlang`.
`ktfmt.javaHome`	string	`""`	Path to a JDK installation. Falls back to `JAVA_HOME`, then `java` on `PATH`. Supports `~` and `$VAR`/`${VAR}`.
`ktfmt.jarPath`	string	`""`	Override path to a ktfmt fat JAR. When set, the bundled version is not downloaded.
`ktfmt.extraArgs`	string[]	`[]`	Extra arguments passed to ktfmt.
`ktfmt.maxWidth`	number \| null	`null`	Override the maximum line width (`--max-width`).
`ktfmt.removeUnusedImports`	boolean	`true`	Remove unused imports. When `false`, passes `--do-not-remove-unused-imports`.
`ktfmt.enableEditorConfig`	boolean	`false`	Pass `--enable-editorconfig` to honor `.editorconfig` overrides for supported options (limited).

Commands

Kotlin: Format with ktfmt (ktfmt.format)
Kotlin: Download/Update ktfmt JAR (ktfmt.downloadJar)
Kotlin: Show ktfmt JAR Path (ktfmt.showJarPath)

How the JAR is managed

The extension is pinned to a specific ktfmt version (declared in the source as SUPPORTED_KTFMT_VERSION). On first format, the matching ktfmt-<version>-with-dependencies.jar is downloaded from Maven Central into VS Code's per-user global storage and verified against a known SHA-256.

When the extension is updated and the supported version changes, the previously cached JAR no longer matches and a fresh download is triggered automatically on the next format.

To pin to your own JAR, set ktfmt.jarPath — the auto-download is bypassed entirely.

Development

pnpm install
pnpm run build         # one-shot build
pnpm run watch         # rebuild on change
pnpm run typecheck     # tsc --noEmit
pnpm run package       # produce a .vsix

Open the project in VS Code and press F5 to launch a new Extension Host with the extension loaded.

License

BSD 3-Clause. See LICENSE.

ktfmt - Kotlin Formatter

omBratteng