PostCSS - Polymer Loader

PostCSS Webpack loader for Polymer elements. Works in combination with the awesome wc-loader.

Install

yarn add --dev postcss-polymer-loader

Setup configurations

Add the postcss configuration file:

postcss.config.js

NOTE: you need to add these (or other) plugins as project dependencies.

module.exports = {
  parser: 'sugarss',
  plugins: {
    'postcss-import': {},
    'postcss-cssnext': {},
    'autoprefixer': {},
    'cssnano': {}
  }
}

Add the loader to your webpack config:

webpack.config.js

module.exports = {
  module: {

    ...

    rules: [

      ...

      {
        test: /\.js$/,
        use: ['babel-loader']  // For ES6 `import`
      }, {
        test: /\.html$/,
        use: ['wc-loader', 'postcss-polymer-loader']
      }
    ]

    ...

  }
}

Setup project

As stated, this loader needs an HTML loader and precisely the wc-loader to load Web Components. More specifically we are talking about Polymer elements.

NOTE: since the wc-loader works well with the Polymer 2.x version, the example will be written in Polymer 2 sintax, but the loader should work also with Polymer 1.x.

Folder structure (example)

|– src
| |– awesome-component
| | |– index.js
| | |- template.html
| | |- style.postcss
| |
| |- global-style.postcss
| |- main-entry.js
|
|– postcss.config.js
|– webpack.config.js

awesome-component/template.html (example)

<!-- This should be resolved by the `wc-loader` -->
<link rel="import" src="./path/to/polymer.html">

<dom-module id="awesome-component">
  <postcss src="./../global-style.postcss"></postcss>
  <postcss src="./style.postcss"></postcss>
  <template>
    <div class="TestDivOne"></div>
    <div class="TestDivTwo"></div>
  </template>
</dom-module>

awesome-component/index.js (example)

'use strict';

// import Polymer from 'polymer'; Aaaaaaaah if we could...!

import './template.html';

class AwesomeComponent extends Polymer.Element {
  static get is() { return 'awesome-component' };
  static get properties() {
    return {
        prop1: {
        type: String,
        value: 'This is awesome!'
      }
    }
  };
};

window.customElements.define(AwesomeComponent.is, AwesomeComponent);

main-entry.js (example)

'use strict';

import './src/awesome-component';

Contribute

This is currently a POC, so if you have some ideas or better solutions just open an issue and let's talk! 👍

License

MIT © LasaleFamine