Haydi

Haydi (pronounced “high-dee”) is an experiment to create an on-demand dev server (like Vite) for Deno.

Open the playground/react directory in your IDE and run deno task dev to see it in action. It will on-demand compile the source files both for the server and the client and run a simple React SSR demo app.

Design

Haydi has a plugin system (internal for now) inspired by Vite’s. It uses plugins to resolve, load, and transform modules both for the server and the browser.

For the server-side code, modules are transformed into an async function body and executed. This will allow hot loading later on. This will be dropped once Deno supports a native loader API.

For the client-side code, modules are transformed and sent to the browser on demand. Bare imports (e.g. import React from "react") are resolved using the import-map.browser.json file and rewritten. Currently, they resolve to CDN versions. We can cache them locally later. Relying on a CDN (even if cached) skirts around the most complicated part of Vite (dependency optimization).

Future plans

• Proper error handling
• Hot reloading and HMR
• Local browser module caching
• CSS and other assets
• Vue, Svelte, Preact, Solid etc.
• Proper CLI
• Configuration options
• External plugin interface
• Production build

Credits

• Fatih Aygün, MIT License
• The “module to function body” transform is adapted from Vite’s SSR transform