Svelte Language Server

A language server (implementing the language server protocol) for Svelte.

Requires Node 12 or later.

What is a language server?

From https://microsoft.github.io/language-server-protocol/overview

The idea behind a Language Server is to provide the language-specific smarts inside a server that can communicate with development tooling over a protocol that enables inter-process communication.

In simpler terms, this allows editor and addon devs to add support for svelte specific 'smarts' (e.g. diagnostics, autocomplete, etc) to any editor without reinventing the wheel.

Features

Svelte language server is under development and the list of features will surely grow over time.

Currently Supported:

• Svelte
  • Diagnostic messages for warnings and errors
  • Svelte specific formatting (via prettier-plugin-svelte)
• HTML (via vscode-html-languageservice)
  • Hover info
  • Autocompletions
  • Emmet
  • Symbols in Outline panel
• CSS / SCSS / LESS (via vscode-css-languageservice)
  • Diagnostic messages for syntax and lint errors
  • Hover info
  • Autocompletions
  • Formatting (via prettier)
  • Emmet
  • Color highlighting and color picker
  • Symbols in Outline panel
• TypeScript / JavaScript (via TypeScript)
  • Diagnostics messages for syntax errors, semantic errors, and suggestions
  • Hover info
  • Formatting (via prettier)
  • Symbols in Outline panel
  • Autocompletions
  • Go to definition
  • Code Actions

How can I use it?

Install a plugin for your editor:

• VS Code

Settings

The language server has quite a few settings to toggle features. They are listed below. When using the VS Code extension, you can set these through the settings UI or in the settings.json using the keys mentioned below.

When using the language server directly, put the settings as JSON inside initializationOptions.configuration for the initialize command. When using the didChangeConfiguration command, pass the JSON directly. The language server also accepts configuration for Emmet (key: emmet; settings reference), Prettier (key: prettier), CSS (key: css / less / scss; settings reference) and TypeScript (keys: javascript and typescript for JS/TS config; settings reference).

Example:

Init:

{
    initializationOptions: {
        configuration: {
            svelte: {
                plugin: {
                    css: { enable: false },
                    // ...
                }
            },
            typescript: { /* .. */ },
            javascript: { /* .. */ },
            prettier: { /* .. */ },
            // ...
        }
    }
}

Update:

{
    svelte: {
        plugin: {
            css: { enable: false },
            // ...
        }
    },
    typescript: { /* .. */ },
    javascript: { /* .. */ },
    prettier: { /* .. */ },
    // ...
    }
}

List of settings

svelte.plugin.typescript.enable

Enable the TypeScript plugin. Default: true

svelte.plugin.typescript.diagnostics.enable

Enable diagnostic messages for TypeScript. Default: true

svelte.plugin.typescript.hover.enable

Enable hover info for TypeScript. Default: true

svelte.plugin.typescript.documentSymbols.enable

Enable document symbols for TypeScript. Default: true

svelte.plugin.typescript.completions.enable

Enable completions for TypeScript. Default: true

svelte.plugin.typescript.codeActions.enable

Enable code actions for TypeScript. Default: true

svelte.plugin.typescript.selectionRange.enable

Enable selection range for TypeScript. Default: true

svelte.plugin.typescript.signatureHelp.enable

Enable signature help (parameter hints) for JS/TS. Default: true

svelte.plugin.typescript.semanticTokens.enable

Enable semantic tokens (semantic highlight) for TypeScript. Default: true

svelte.plugin.css.enable

Enable the CSS plugin. Default: true

svelte.plugin.css.globals

Which css files should be checked for global variables (--global-var: value;). These variables are added to the css completions. String of comma-separated file paths or globs relative to workspace root.

svelte.plugin.css.diagnostics.enable

Enable diagnostic messages for CSS. Default: true

svelte.plugin.css.hover.enable

Enable hover info for CSS. Default: true

svelte.plugin.css.completions.enable

Enable auto completions for CSS. Default: true

svelte.plugin.css.completions.emmet

Enable emmet auto completions for CSS. Default: true If you want to disable emmet completely everywhere (not just Svelte), you can also set "emmet.showExpandedAbbreviation": "never" in your settings.

svelte.plugin.css.documentColors.enable

Enable document colors for CSS. Default: true

svelte.plugin.css.colorPresentations.enable

Enable color picker for CSS. Default: true

svelte.plugin.css.documentSymbols.enable

Enable document symbols for CSS. Default: true

svelte.plugin.css.selectionRange.enable

Enable selection range for CSS. Default: true

svelte.plugin.html.enable

Enable the HTML plugin. Default: true

svelte.plugin.html.hover.enable

Enable hover info for HTML. Default: true

svelte.plugin.html.completions.enable

Enable auto completions for HTML. Default: true

svelte.plugin.html.completions.emmet

Enable emmet auto completions for HTML. Default: true If you want to disable emmet completely everywhere (not just Svelte), you can also set "emmet.showExpandedAbbreviation": "never" in your settings.

svelte.plugin.html.tagComplete.enable

Enable HTML tag auto closing. Default: true

svelte.plugin.html.documentSymbols.enable

Enable document symbols for HTML. Default: true

svelte.plugin.html.linkedEditing.enable

Enable Linked Editing for HTML. Default: true

svelte.plugin.svelte.enable

Enable the Svelte plugin. Default: true

svelte.plugin.svelte.diagnostics.enable

Enable diagnostic messages for Svelte. Default: true

svelte.plugin.svelte.compilerWarnings

Svelte compiler warning codes to ignore or to treat as errors. Example: { 'css-unused-selector': 'ignore', 'unused-export-let': 'error'}

svelte.plugin.svelte.format.enable

Enable formatting for Svelte (includes css & js) using prettier-plugin-svelte. Default: true

You can set some formatting options through this extension. They will be ignored if there's any kind of configuration file, for example a .prettierrc file. Read more about Prettier's configuration file here.

svelte.plugin.svelte.format.config.svelteSortOrder

Format: join the keys options, scripts, markup, styles with a - in the order you want. Default: options-scripts-markup-styles

This option is ignored if there's any kind of configuration file, for example a .prettierrc file.

svelte.plugin.svelte.format.config.svelteStrictMode

More strict HTML syntax. Default: false

This option is ignored if there's any kind of configuration file, for example a .prettierrc file.

svelte.plugin.svelte.format.config.svelteAllowShorthand

Option to enable/disable component attribute shorthand if attribute name and expression are the same. Default: true

This option is ignored if there's any kind of configuration file, for example a .prettierrc file.

svelte.plugin.svelte.format.config.svelteBracketNewLine

Put the > of a multiline element on a new line. Default: true

This option is ignored if there's any kind of configuration file, for example a .prettierrc file.

svelte.plugin.svelte.format.config.svelteIndentScriptAndStyle

Whether or not to indent code inside <script> and <style> tags. Default: true

This option is ignored if there's any kind of configuration file, for example a .prettierrc file.

svelte.plugin.svelte.format.config.printWidth

Maximum line width after which code is tried to be broken up. This is a Prettier core option. If you have the Prettier extension installed, this option is ignored and the corresponding option of that extension is used instead. This option is also ignored if there's any kind of configuration file, for example a .prettierrc file. Default: 80

svelte.plugin.svelte.format.config.singleQuote

Use single quotes instead of double quotes, where possible. This is a Prettier core option. If you have the Prettier extension installed, this option is ignored and the corresponding option of that extension is used instead. This option is also ignored if there's any kind of configuration file, for example a .prettierrc file. Default: false

svelte.plugin.svelte.hover.enable

Enable hover info for Svelte (for tags like #if/#each). Default: true

svelte.plugin.svelte.completions.enable

Enable autocompletion for Svelte (for tags like #if/#each). Default: true

svelte.plugin.svelte.rename.enable

Enable rename/move Svelte files functionality. Default: true

svelte.plugin.svelte.codeActions.enable

Enable code actions for Svelte. Default: true

svelte.plugin.svelte.selectionRange.enable

Enable selection range for Svelte. Default: true

svelte.plugin.svelte.runesLegacyModeCodeLens.enable

Whether or not to show a code lens at the top of Svelte files indicating if they are in runes mode or legacy mode. Only visible in Svelte 5 projects. Default: true

svelte.plugin.svelte.defaultScriptLanguage

The default language to use when generating new script tags in Svelte. Default: none

Credits

• James Birtles for creating the foundation which this language server is built on
• Vue's Vetur language server which heavily inspires this project