Herb Language Server

Package: @herb-tools/language-server

Language Server Protocol integration for HTML-aware ERB parsing using the Herb Parser.

Installation

Visual Studio Code

Install the Herb LSP extension from the Visual Studio Marketplace.

Cursor (Open VSX Registry)

Install the Herb LSP extension from the Open VSX Registry.

Zed

The Herb Language Server is part of the official Ruby extension for Zed. Just install the Ruby extension in Zed and you should be good to go.

Read more in the documentation.

Neovim (using nvim-lspconfig)

After installing the Herb Language Server (see below), add herb_ls to your Neovim config (requires nvim 0.11+):

require('lspconfig')
vim.lsp.enable('herb_ls')

Sublime Text (using Sublime LSP)

After installing the Herb Language Server (see below) and Sublime LSP, update the preferences for the LSP package:

// LSP.sublime-settings
{
  "clients": {
    "herb": {
      "enabled": true,
      "command": [
        "herb-language-server",
        "--stdio"
      ],
      "selector": "text.html.ruby | text.html.rails",
      "settings": {
        "languageServerHerb.linter": {
          "enabled": true,
          "excludedRules": ["parser-no-errors"]
        }
      },
      "initializationOptions": {
        "enabledFeatures": {
          "diagnostics": true,
        },
        "experimentalFeaturesEnabled": true
      }
    }
  },
}

Manual Installation

You can use the language server in any editor that supports the Language Server Protocol.

NPM (Global)

npm install -g @herb-tools/language-server

Yarn (Global)

yarn global add @herb-tools/language-server

Preview Releases

Want to try unreleased features? Use pkg.pr.new to run the language server from any commit or PR:

npx https://pkg.pr.new/@herb-tools/language-server@{commit} --stdio

Replace {commit} with a commit SHA (e.g., 0d2eabe) or branch name (e.g., main). Find available previews at pkg.pr.new/~/marcoroth/herb.

Run

herb-language-server --stdio

Usage

Usage: herb-language-server [options]

Options:

  --stdio          use stdio
  --node-ipc       use node-ipc
  --socket=<port>  use socket

NPX

Alternatively you can also run the language server directly with npx without installing anything:

npx @herb-tools/language-server --stdio

Configuration

The language server can be configured using a .herb-lsp/config.json file in your project root. This file is automatically created when the language server starts if it doesn't exist.

Formatter Configuration

You can configure formatting behavior by adding a formatter section to your config:

{
  "version": "0.3.1",
  "createdAt": "2025-06-29T00:00:00.000Z",
  "updatedAt": "2025-06-29T00:00:00.000Z",
  "options": {
    "formatter": {
      "enabled": true,
      "indentWidth": 2,
      "maxLineLength": 80
    }
  }
}

formatter Options

• enabled (boolean): Enable or disable formatting for this project. Defaults to false.
• indentWidth (number): Number of spaces for each indentation level. Defaults to 2.
• maxLineLength (number): Maximum line length before wrapping. Defaults to 80.

Note: VS Code users can also control formatting globally through the languageServerHerb.formatter.enabled setting in VS Code preferences. Formatting is currently in Beta and disabled by default.