Sapper + Svelte Image + Tailwind CSS

_layout.svelte

<script>
	import Nav from '../components/Nav.svelte';

	export let segment;
</script>

<Nav {segment}/>

<main>
	<slot></slot>
</main>

<style global lang="postcss">
  /* https://www.swyx.io/svelte_tailwind_setup/#step-3-add-the-tailwind-includes-to-your-svelte-app */
  
  /* only apply purgecss on utilities, per Tailwind docs */
  /* purgecss start ignore */
  @tailwind base;
  @tailwind components;
  /* purgecss end ignore */

  @tailwind utilities;

</style>

rollup.config.js

import path from 'path';
import resolve from '@rollup/plugin-node-resolve';
import replace from '@rollup/plugin-replace';
import commonjs from '@rollup/plugin-commonjs';
import url from '@rollup/plugin-url';
import svelte from 'rollup-plugin-svelte';
import babel from '@rollup/plugin-babel';
import { terser } from 'rollup-plugin-terser';
import config from 'sapper/config/rollup.js';
import pkg from './package.json';
import seqPreprocessor from 'svelte-sequential-preprocessor';
import autoPreprocess from 'svelte-preprocess';
import image from 'svelte-image';


const mode = process.env.NODE_ENV;
const dev = mode === 'development';
const legacy = !!process.env.SAPPER_LEGACY_BUILD;
const production = !process.env.ROLLUP_WATCH;

const onwarn = (warning, onwarn) =>
	(warning.code === 'MISSING_EXPORT' && /'preload'/.test(warning.message)) ||
	(warning.code === 'CIRCULAR_DEPENDENCY' && /[/\\]@sapper[/\\]/.test(warning.message)) ||
	onwarn(warning);

// https://stackoverflow.com/questions/62446218/change-the-order-of-preprocessors-in-svelte-sapper
// https://www.npmjs.com/package/svelte-sequential-preprocessor
const preprocess = seqPreprocessor([
	autoPreprocess({
		sourceMap: !production,
		postcss: {
			plugins: [
				require("tailwindcss"),
				require("autoprefixer"),
				require("postcss-nesting")
			],
		},
	}), 
	image({
		inlineBelow: 10000,
		placeholder: 'blur', //blur
	})
]);

export default {
	client: {
		input: config.client.input(),
		output: config.client.output(),
		plugins: [
			replace({
				'process.browser': true,
				'process.env.NODE_ENV': JSON.stringify(mode)
			}),
			svelte({
				preprocess: preprocess,
				compilerOptions: {
					dev,
					hydratable: true
				}
			}),
			url({
				sourceDir: path.resolve(__dirname, 'src/node_modules/images'),
				publicPath: '/client/'
			}),
			resolve({
				browser: true,
				dedupe: ['svelte']
			}),
			commonjs(),

			legacy && babel({
				extensions: ['.js', '.mjs', '.html', '.svelte'],
				babelHelpers: 'runtime',
				exclude: ['node_modules/@babel/**'],
				presets: [
					['@babel/preset-env', {
						targets: '> 0.25%, not dead'
					}]
				],
				plugins: [
					'@babel/plugin-syntax-dynamic-import',
					['@babel/plugin-transform-runtime', {
						useESModules: true
					}]
				]
			}),

			!dev && terser({
				module: true
			})
		],

		preserveEntrySignatures: false,
		onwarn,
	},

	server: {
		input: config.server.input(),
		output: config.server.output(),
		plugins: [
			replace({
				'process.browser': false,
				'process.env.NODE_ENV': JSON.stringify(mode)
			}),
			svelte({
				compilerOptions: {
					dev,
					generate: 'ssr',
					hydratable: true
				},
				emitCss: false
			}),
			url({
				sourceDir: path.resolve(__dirname, 'src/node_modules/images'),
				publicPath: '/client/',
				emitFiles: false // already emitted by client build
			}),
			resolve({
				dedupe: ['svelte']
			}),
			commonjs()
		],
		external: Object.keys(pkg.dependencies).concat(require('module').builtinModules),

		preserveEntrySignatures: 'strict',
		onwarn,
	},

	serviceworker: {
		input: config.serviceworker.input(),
		output: config.serviceworker.output(),
		plugins: [
			resolve(),
			replace({
				'process.browser': true,
				'process.env.NODE_ENV': JSON.stringify(mode)
			}),
			commonjs(),
			!dev && terser()
		],

		preserveEntrySignatures: false,
		onwarn,
	}
};

tailwind.config.js

// Add a tailwind.config.js file at the project root
// https://www.swyx.io/svelte_tailwind_setup/
const isProduction = !process.env.ROLLUP_WATCH; // or some other env var like NODE_ENV
module.exports = {
    // only needed in Tailwind 1.0 for tailwind 2.0 compat
    // future: { 
    //     purgeLayersByDefault: true, 
    //     removeDeprecatedGapUtilities: true,
    //   },
    plugins: [
        // for tailwind UI users only
        // require('@tailwindcss/ui'),
        // other plugins here
    ],
    purge: {
        content: [
            "./src/**/*.svelte",
            // may also want to include HTML files
            // "./src/**/*.html"
        ],
        // this is for extracting Svelte `class:` syntax but is not perfect yet, see below
        defaultExtractor: content => {
            const broadMatches = content.match(/[^<>"'`\s]*[^<>"'`\s:]/g) || []
            const broadMatchesWithoutTrailingSlash = broadMatches.map(match => _.trimEnd(match, '\\'))
            const matches = broadMatches
                .concat(broadMatchesWithoutTrailingSlash)
            return matches
        },
        enabled: isProduction // disable purge in dev
    },
};