Serve Vite-based Ember apps from development server

[tricknotes]

Summary

Add support for serving Vite-based Ember applications (generated with ember-cli >= 6.8) from Vite's own development server in development mode, enabling hot module reloading without restarting Rails.

Key Changes

• New DevServer class (lib/ember_cli/dev_server.rb): Manages the Vite development server lifecycle for a single Ember application

  • Boots the server lazily on first request
  • Detects if a server is already listening and reuses it
  • Provides HTTP methods (get, head, options_request) to fetch assets and HTML from the server
  • Handles timeouts and connection failures with helpful error messages

• New DevServerProxy Rack middleware (lib/ember_cli/dev_server_proxy.rb): Proxies requests to the development server

  • Forwards GET, HEAD, and OPTIONS requests
  • Strips hop-by-hop headers to avoid connection issues
  • Rejects unsupported HTTP verbs with 405 responses

• New Deploy::DevServer strategy (lib/ember_cli/deploy/dev_server.rb): Serves applications from the development server

  • Rewrites root-relative URLs in index.html to absolute URLs pointing at the development server
  • Enables Vite's HMR client to connect directly to the development server

• Enhanced App class (lib/ember_cli/app.rb):

  • Adds dev_server? method to detect when an app should use the development server
  • Adds dev_server property to lazily initialize the DevServer
  • Selects Deploy::DevServer strategy by default for Vite-based apps in development
  • Supports dev_server configuration option to customize host, port, and timeout

• Enhanced Shell class (lib/ember_cli/shell.rb):

  • Adds start_dev_server method to spawn the Vite development server in a separate process group
  • Adds dev_server_running? method to check server status
  • Properly signals and cleans up the development server process on exit

• Enhanced Command class (lib/ember_cli/command.rb): Adds dev_server method to construct the Vite CLI command

• Enhanced PathSet class (lib/ember_cli/path_set.rb): Adds vite property to locate the Vite executable

• Comprehensive test coverage: Includes unit tests for all new classes and integration tests verifying the full request flow

Notable Implementation Details

• The development server is started in its own process group, allowing Rails to cleanly shut down the entire server tree on exit
• Root-relative URLs in index.html are rewritten to absolute URLs so the browser loads Vite's HMR client directly from the development server, not through Rails
• Assets referenced relatively by the Ember application are still proxied through Rails, maintaining compatibility with the existing asset pipeline
• The implementation gracefully falls back to reusing an existing server if one is already listening on the configured host and port, enabling manual npm start workflows
• Configuration is optional; sensible defaults (127.0.0.1, available port, 30-second timeout) are provided