Extensions

Radius uses VSCode extensions for language support. Extensions provide LSP server configurations and language definitions.

Install Extensions

From Open VSX Registry

radius ext install <publisher>.<name>

Example:

radius ext install rust-lang.rust-analyzer

This downloads the extension from Open VSX and extracts it to ~/.radius/extensions/.

From Local Directory

radius ext install ./path/to/extension

Useful for development or custom extensions.

List Extensions

radius ext list

Output:

Installed extensions:

  rust-lang.rust-analyzer  v0.4.2900 [ra_syntax_tree, rust]
  test.test-extension      v1.0.0    [typescript]

Each extension shows:

• Publisher and name
• Version
• Supported language IDs

Remove Extensions

radius ext remove <publisher>.<name>

Example:

radius ext remove rust-lang.rust-analyzer

How Extensions Work

Language Detection

Extensions define file extension mappings in package.json:

{
  "contributes": {
    "languages": [{
      "id": "rust",
      "extensions": [".rs"]
    }]
  }
}

When you run radius read-var file.rs, Radius:

1. Finds .rs → rust mapping from extensions
2. Looks up LSP server for rust language
3. Starts the LSP server if needed
4. Sends requests to the server

LSP Server Detection

Radius uses static extraction to find LSP servers:

1. Scans extension directories for server binaries (server/, bin/)
2. Falls back to PATH using language ID → command mapping
3. User config in ~/.radius/lsp-servers.json

Check detected servers:

radius lsp list

language            command                                 source
--------------------------------------------------------------------------------
typescript          typescript-language-server --stdio      extension (test.test-extension)
rust                rust-analyzer                           extension (rust-lang.rust-analyzer)
python              pylsp                                   user-config (~/.radius/lsp-servers.json)
go                  gopls                                   fallback

Source Priority

1. extension - Extracted from installed extension
2. user-config - Defined in ~/.radius/lsp-servers.json
3. fallback - Built-in default mapping

Creating Extensions

For custom language support, create a minimal extension:

Directory Structure

my-extension/
├── package.json
└── (optional) server/
    └── language-server

package.json

{
  "name": "my-language-support",
  "publisher": "my-org",
  "version": "1.0.0",
  "engines": {
    "vscode": "^1.70.0"
  },
  "contributes": {
    "languages": [{
      "id": "mylang",
      "extensions": [".mylang", ".ml"]
    }]
  }
}

Install

radius ext install ./my-extension

Configure LSP

If the server isn't bundled, add to ~/.radius/lsp-servers.json:

{
  "servers": {
    "mylang": {
      "command": "mylang-lsp",
      "args": ["--stdio"]
    }
  }
}