feat(unplugin): new unplugin package. Run stencil code in most bundlers

[johnjenkins]

What is the current behavior?

GitHub Issue Number: N/A

What is the new behavior?

Introduces @stencil/unplugin - a universal bundler plugin that lets you run Stencil code directly in Vite, Rollup, Webpack, esbuild, and Rspack projects without a full Stencil compiler / build pipeline.

Each .tsx component file is transpiled on-the-fly via transpileSync into a self-registering custom element. Only files containing Stencil decorators are transformed; everything else passes through untouched.

Key features:

• Drop-in plugin for all major bundlers - one line of config
• CSS pipeline with optional Sass, Less, PostCSS, and lightningcss support (peer deps, silently skipped if absent)
• HMR support: Vite uses a WebSocket patch strategy; Webpack/Rspack use module.hot prototype patching
• Optional docs: true mode exposes a Custom Elements Manifest via a virtual module (@stencil/unplugin/docs)

Quick usage (Vite):

// vite.config.ts
import { stencilVite } from '@stencil/unplugin';
export default defineConfig({ plugins: [stencilVite()] });

Quick usage (Webpack):

// webpack.config.js
const { stencilWebpack } = require('@stencil/unplugin');
module.exports = { plugins: [stencilWebpack()] };

Accessing the CEM (docs mode):

import cem from '@stencil/unplugin/docs';
console.log(cem.modules);

Documentation

Does this introduce a breaking change?

• Yes
• No

Testing

Other information