A plugin for esbuild that allows importing CSS, SVG, HTML, XLIFF files as tagged-template literals. The files are (optionally) minified using esbuild minifier (for CSS), html-minifier (for HTML), and svgo (for SVG).

npm i esbuild-plugin-lit -D

Include plugin in your build script:

const { default: litPlugin } = require("esbuild-plugin-lit");

require("esbuild").build({
  entryPoints: ["index.ts"],
  bundle: true,
  outfile: "index.js",
  minify: true,
  plugins: [litPlugin()],
});

Now you can import CSS, SVG, HTML files as tagged-template literals:

import styles from 'styles.css';
import icon from 'icon.svg';

class SpecialButton extends LitElement {
  static styles = styles;
  ...
  render() {
    return html`
      <button>
        <span class="icon">${icon}</span>
      </button>
    `
  }
}

For TypeScript support, include ambient module types in your config file:

{
  "include": ["./node_modules/esbuild-plugin-lit/modules.d.ts"]
}

The plugin supports setting custom file extensions and transformation for each imported types, for example, the following with load SASS files:

const { default: litPlugin } = require("esbuild-plugin-lit");
const SASS = require("sass");

require("esbuild").build({
  ...
  plugins: [litPlugin(
    {
      // augment the global filter
      filter: /\.(css|svg|html|xlf|scss)$/,
      css: {
        // specify extension for css
        extension: /\.s?css$/,
        transform: (data) => Sass.renderSync({ data }).css.toString(),
      },
    },
  )],
});

If minification is set for esbuild (minify: true), the plugin will minify imported CCS files using esbuild's built-in minifier. You can set minify: false in settings for CSS to opt-out from minification:

require("esbuild").build({
  ...
  plugins: [litPlugin({
    css: {
      minify: false,
    },
  })],
});

To minify SVG and HTML files, the plugin uses svgo and html-minifier packages respectively, so make sure they are installed if such minification is required:

npm i svgo -D
npm i html-minifier -D

Then supply the minifiers' options to the plugin:

require("esbuild").build({
  ...
  minify: true,
  plugins: [litPlugin({
    svg: {
      svgo: {
        plugins: [
          "preset-default",
          "removeXMLNS",
        ],
      },
    },
    html: {
      htmlMinifier: {}, // use the default options
    },
  })],
});

Lit provides lit-localize package for localization purposes. When used in the so-called runtime mode, the package relies on a set of rollup based tools to extract messages from templates into XLIFF localization files (lit-localize extract), and to later compile them into "importable" JS files using lit-localize build.

With esbuild-plugin-lit one can skip the build step and "load" XLIFF files directly as shown in our example project:

...
// Load xliff files statically
import * as ce from "./xliff/ce.xlf";
import * as es from "./xliff/es.xlf";

const locales = new Map(
  [["ce", ce], ["es", es]],
);

const { setLocale } = configureLocalization({
  sourceLocale: "en",
  targetLocales: ["ce", "es"],
  loadLocale: async (locale) => locales.get(locale),
});
...

The files are compiled on the fly by esbuild, thus, simplifying the toolchain and speeding up the process.

To load XLIFF files, install tmxl:

npm i txml -D

And set xlf option:

require("esbuild").build({
  ...
  loader: {
    ".xlf": "text",
  },
  plugins: [litPlugin({
    xlf: {}, // use default settings
  })],
});

The plugin also supports building with Deno:

import * as esbuild from "https://deno.land/x/[email protected]/mod.js";
import { denoPlugin } from "https://deno.land/x/[email protected]/mod.ts";
import pluginLit from "https://raw.githubusercontent.com/zandaqo/esbuild-plugin-lit/master/mod.ts";

await esbuild
  .build({
    plugins: [
      pluginLit({
        specifier: "https://cdn.skypack.dev/[email protected]?dts",
      }),
      denoPlugin(),
    ],
    entryPoints: ["./main.ts"],
    outfile: "./main.js",
    target: "es2022",
    format: "esm",
    bundle: true,
    minify: true,
    sourcemap: true,
  });

esbuild.stop();

Though, keep in mind that Deno does not support ambient module typing (declare module) and each asset import has to be typed using // @deno-types.

MIT @ Maga D. Zandaqo