rsvelte for VS Code

Rust-powered formatting and linting for Svelte, powered by rsvelte — a port of the Svelte compiler to Rust. This extension bundles @rsvelte/language-server and launches it over stdio.

Features

• Syntax highlighting for .svelte files (including <script lang="ts">, <style lang="scss|less|postcss|sass|stylus">, <template lang="pug">, and ```svelte code blocks in Markdown), plus Svelte-aware bracket matching, auto-closing, folding, and snippets. The official Svelte extension is not required.
• Format on demand / on save via the native rsvelte-fmt CLI. Works for .svelte plus the JS/TS/CSS/JSON families (everything is dispatched to oxfmt internally for a complete format).
• Inline diagnostics from the bundled rsvelte_lint engine (compiler warnings + a11y + native rules). No extra install — the linter ships inside the extension as wasm.

That's the full feature set — hover, completion, go-to-definition, rename, find-references, and TypeScript diagnostics are not provided (this is a formatter + linter, not a full language server). Those wait on tsgo's tsserver mode landing upstream; until then, use @rsvelte/svelte-check for batch type-checking.

Requirements

Formatting requires the native rsvelte-fmt binary. Install it in your project:

npm install -D @rsvelte/fmt

The extension resolves node_modules/.bin/rsvelte-fmt from the workspace. If it isn't found, formatting is disabled (linting still works). You can point at a specific binary with rsvelte.rsvelteFmtPath.

Using it alongside the official Svelte extension

This extension ships its own Svelte grammar and language definition, so it is a standalone replacement for svelte.svelte-vscode. Running both at once duplicates diagnostics, completions and hovers, makes VS Code prompt for which formatter to use, and leaves it up to activation order which copy of the source.svelte grammar ends up registered. The extension warns once if it detects the official extension — disable one of the two.

Setup as the default formatter

To format Svelte files with rsvelte, set it as the default formatter (so it doesn't conflict with the official Svelte extension):

// .vscode/settings.json
{
  "[svelte]": {
    "editor.defaultFormatter": "rsvelte.rsvelte-vscode"
  }
}

Settings

Lint configuration

Which rules run, at what severity, comes from a rsvelte-lint.json (or .rsvelte-lintrc.json) in your project — the same file the rsvelte-lint CLI reads, found by walking up from the file being linted, so the editor reports what CI does:

{
  "rules": {
    "svelte/no-unused-class-name": "off",
    "svelte/no-at-html-tags": "error"
  }
}

Without one, every rule runs at its default severity — noisy in a codebase that has never been linted with rsvelte. Start from nothing with "extends": ["none"] and opt rules in, or turn off the ones your project already covers elsewhere (e.g. via eslint-plugin-svelte). Saving the config applies it immediately. See the configuration reference for the full shape.

License

MIT. The bundled grammars, snippets and language configurations are copied from sveltejs/language-tools (MIT) — see THIRD_PARTY_NOTICES.md.