rjsv-websocket

A plugin for rjsv that starts a local WebSocket server and allows external applications to monitor the file transpilation state.

The server sends a notification whenever transpilation finishes, so other tools can react to changes (e.g. live reload, build automation, etc.).

Installation

The plugin requires the em-websocket Ruby gem (which automatically installs eventmachine as a dependency):

gem install em-websocket

Recommended installation: place the plugin in your $HOME/.rjsv/plugins directory.

For more details, see the official documentation: Plugins

Usage

The plugin is enabled by adding the websocket argument to the end of the rjsv command.

It is recommended to place it at the end so that subsequent flags are processed by the main application instead of the plugin.

The WebSocket server starts only when file watching (watch mode) is enabled.

Example

rjsv -t -w -s 'src/rb' -o 'src/js' websocket

WebSocket Server

After startup, a local WebSocket server runs at:

ws://localhost:7071

Messages

When transpilation completes, the server sends the following message to all connected clients:

{ "type": "update" }

Typical Use Cases

• frontend live reload
• build process synchronization
• integration with developer tools

Architecture Overview

        ┌───────────────────────┐
        │  RJSV::CLI::States    │
        │  (watch_state)        │
        └─────────┬─────────────┘
                  │ tracks files
                  ▼
        ┌───────────────────────┐
        │  File System Events   │
        │  (added, modified,    │
        │   removed)            │
        └─────────┬─────────────┘
                  │ trigger
                  ▼
        ┌─────────────────────────────┐
        │ RJSV::Plugins::Websocket    │
        │           States            │
        │ (create_server, send_update)│
        └─────────┬───────────┬───────┘
                  │           │
                  │ send      │ server lifecycle
                  ▼           ▼
        ┌─────────────────────────────┐
        │  WebSocket Server           │
        │  (ws://localhost:7071)      │
        └─────────────────────────────┘
                  │
                  │ notification "update"
                  ▼
        ┌─────────────────────────────┐
        │ Connected Clients / Tools   │
        │ (live reload, build sync)   │
        └─────────────────────────────┘

This diagram shows how the CLI, WebSocket plugin, server, and connected clients interact.