File watcher that triggers recompilation, Tailwind rebuilds, and HMR updates.

Monitors source directories for changes, recompiles affected JS/Vue/CSS files through the Pipeline, triggers Tailwind CSS rebuilds when template files change, and broadcasts updates to connected HMR clients.

When a JS/TS/Vue file changes, the watcher attempts to find an HMR boundary (a module with import.meta.hot.accept()) by walking up the dependency graph. If found, only that module is re-imported by the client. Otherwise, a full page reload is triggered.

Options

• :root — asset source directory (required, e.g. "assets")
• :watch_dirs — additional directories to watch for Tailwind scanning (e.g. ["lib/"] for .ex/.heex templates)
• :tailwind — enable Tailwind CSS rebuilds (default: false)
• :tailwind_css — custom Tailwind input CSS (default: Tailwind base)
• :target — JS downlevel target
• :import_source — JSX import source
• :vapor — Vue Vapor mode