Deno Lsp

deno-lsp

Full Deno LSP integration for Claude Code, providing real-time code intelligence and comprehensive Deno development guidance.

Features

LSP Integration (via MCP)

Full deno lsp integration providing:

• Diagnostics - Real-time error and warning detection
• Hover - Type information and documentation on hover
• Go-to-Definition - Navigate to symbol definitions
• Code Actions - Quick fixes and refactoring suggestions
• Completions - Intelligent code completion

Supported File Extensions

.ts, .tsx, .js, .jsx, .mts, .cts, .mjs, .cjs

Skills

This plugin includes comprehensive Deno development guidance:

Skill	Focus
deno-typescript	Quick reference for Deno TypeScript development
deno-core	Configuration, imports, testing, permissions, anti-patterns
deno-ddd	Domain-Driven Design architecture patterns
deno-patterns	Modern TypeScript patterns, resource management, migration

Prerequisites

Install Deno globally:

curl -fsSL https://deno.land/install.sh | sh

Or with Homebrew:

brew install deno

Verify installation:

deno --version

Requirements

• Deno >= 2.0 (for full LSP support)
• deno.json or deno.jsonc in project root (plugin only activates in Deno projects)
• ENABLE_LSP_TOOL=1 environment variable (see Enabling LSP below)

Enabling LSP

Claude Code requires the ENABLE_LSP_TOOL environment variable to be set for version < 2.1.1:

Temporary (current session):

ENABLE_LSP_TOOL=1 claude

Permanent (add to shell profile):

# Add to ~/.bashrc, ~/.zshrc, or equivalent:
export ENABLE_LSP_TOOL=1

After enabling, restart Claude Code for the LSP to initialize

Usage

LSP Features

The LSP integration activates automatically when you work with TypeScript/JavaScript files in a Deno project. Claude will receive diagnostics, type information, and suggestions from the Deno language server.

Skills

Skills activate automatically based on context:

• Ask about Deno configuration, imports, or testing → deno-core activates
• Work on complex business logic or architecture → deno-ddd activates
• Ask about modern patterns or Node.js migration → deno-patterns activates
• Quick questions about Deno → deno-typescript activates

Configuration

No configuration required. The plugin uses your project's deno.json for LSP settings.

LSP Configuration

The plugin configures the Deno LSP with these defaults (in .lsp.json and plugin.json):

{
  "typescript": {
    "command": "deno",
    "args": [
      [
        "lsp"
      ]
    ],
    "extensionToLanguage": {
      ".ts": "typescript",
      ".tsx": "typescriptreact",
      ".js": "javascript",
      ".jsx": "javascriptreact",
      ".mts": "typescript",
      ".cts": "typescript",
      ".mjs": "javascript",
      ". cjs": "javascript"
    },
    "transport": "stdio",
    "initializationOptions": {
      "enable": true,
      "enablePaths": [
        "src",
        "tests",
        "fixtures"
      ],
      "lint": true,
      "unstable": false,
      "suggest": {
        "autoImports": true,
        "imports": {
          "autoDiscover": true
        }
      }
    },
    "maxRestarts": 3
  }
}

Note: The server key is "typescript" to match the language identifiers in extensionToLanguage. This ensures Deno LSP handles TypeScript files as the default server.

Available LSP Settings

Setting	Description
enable	Enable/disable Deno LSP
lint	Enable linting
unstable	Enable unstable APIs
config	Path to deno.json
importMap	Path to import map
suggest.autoImports	Enable auto-import suggestions
codeLens.test	Show test code lens

Custom Project Settings

Add the lint section to your deno.json file to configure project-specific LSP settings:

{
  "lint": {
    "rules": {
      "include": [
        "no-external-import"
      ]
    },
    "include": [
      "src/"
    ],
    "exclude": [
      ".tmp/",
    ]
  }
}

LSP not using Deno for TypeScript

If another LSP (like typescript-language-server) handles TypeScript instead of Deno:

• The deno-lsp plugin registers for the "typescript" language identifier
• Disable conflicting TypeScript LSP plugins in settings
• Ensure deno-lsp is enabled and loaded first

Debug Mode

Run Claude Code with debug logging to see LSP initialization:

claude --debug

Look for log lines mentioning "LSP" or "deno" to verify the server starts.

More Information

• Deno Runtime Documentation
• Deno Standard Library
• JSR Registry
• GitHub Repository