esbuild-plugin-lit-css

esbuild-plugin-lit-css

ESBuild plugin to import css files as JavaScript tagged-template literal objects.

The "Lit" stands for "Literal"

You can use it to import CSS for various libraries like lit-element, @microsoft/fast-element, or others.

Do I Need This?

No. This is an optional package who's sole purpose is to make it easier to write CSS-in-CSS while working on lit-element projects. You can just as easily write your CSS in some 'styles.css.js' modules a la:

import { css } from 'lit-element';
export default css`:host { display: block; }`;

And this may actually be preferred.

Hopefully this package will become quickly obsolete when the CSS Modules Proposal (or something like it) is accepted and implemented.

In the mean time, enjoy importing your CSS into your component files.

Options

Name	Accepts	Default
filter	RegExp of file names to apply to	/\.css$/i
cssnano	Boolean or Object of cssnano options.	false
specifier	Package to import css from	lit
tag	Name of the template-tag function	css
transform	Optional function (sync or async) which transforms css sources (e.g. postcss)	x => x

Usage

import esbuild from 'esbuild';
import { litCssPlugin } from 'esbuild-plugin-lit-css';

await esbuild.build({
  ...theRestOfYourConfig,
  plugins: [
    litCssPlugin(),
  ],
});

Then import your CSS:

:host {
  display: block;
}

h1 {
  color: hotpink;
}

import { LitElement, customElement, html } from 'lit-element';

import style from './css-in-css.css';

@customElement('css-in-css')
class CSSInCSS extends LitElement {
  static get styles() {
    return [style];
  }

  render() {
    return html`<h1>It's Lit!</h1>`;
  }
}

Usage with FAST

plugins: [
  litcss({ specifier: '@microsoft/fast-element' })
]

import { FASTElement, customElement, html } from '@microsoft/fast-element';

import styles from './css-in-css.css';

const template = html<CSSinCSS>`<h1>It's Lit!</h1>`;

@customElement({ name: 'css-in-css', template, styles })
class CSSinCSS extends FASTElement {}

Usage with Sass, Less, PostCSS, etc.

To load scss files:

1. Specify the filter option to litCssPlugin to include scss files
2. Define a transform function in the plugin options.

// esbuild script
import esbuild from 'esbuild';
import Sass from 'sass';

await esbuild.build({
  entryPoints: [/*...*/],
  plugins: [
    litCssPlugin({
      filter: /.scss$/,
      transform: (data, { filePath }) =>
        Sass.renderSync({ data, file: filePath })
          .css.toString(),
    }),
  ]
});

Similarly, to transform sources using PostCSS, specify a transform function:

import esbuild from 'esbuild';
import postcss from 'postcss';
import postcssNesting from 'postcss-nesting';

const processor = postcss(postcssNesting());

await esbuild.build({
  entryPoints: [/*...*/],
  plugins: [
    litCssPlugin({
      transform: (css, { filePath }) =>
        processor.process(css, { from: filePath })
          .css,
    }),
  ]
});

Looking for webpack? lit-css-loader Looking for rollup? rollup-plugin-lit-css Looking for typescript? typescript-transform-lit-css