Troubles combining bundling Svelte Material UI with custom SCSS using Rollup

Question

I have Svelte 3.x (with TS enabled) and a pretty standard Rollup config for bundling my SCSS files with this file structure:

| src
|   styles.scss
|   etc.

rollup.config.js:

export default {
    input: 'src/main.ts',
    output: {
        sourcemap: true,
        format: 'iife',
        name: 'myapp',
        file: 'public/build/bundle.js'
    },
    plugins: [
        svelte({
            // enable run-time checks when not in production
            dev: !production,
            // we'll extract any component CSS out into
            // a separate file - better for performance
            css: css => {
                css.write('bundle.css');
            },
            preprocess: autoPreprocess(),
        }),

        // If you have external dependencies installed from
        // npm, you'll most likely need these plugins. In
        // some cases you'll need additional configuration -
        // consult the documentation for details:
        // https://github.com/rollup/plugins/tree/master/packages/commonjs
        resolve({
            browser: true,
            dedupe: ['svelte']
        }),
        commonjs(),
        typescript({ sourceMap: !production }),

        // In dev mode, call `npm run start` once
        // the bundle has been generated
        !production && serve(),

        // Watch the `public` directory and refresh the
        // browser on changes when not in production
        !production && livereload('public'),

        // If we're building for production (npm run build
        // instead of npm run dev), minify
        production && terser()
    ],
    watch: {
        clearScreen: false
    }
};

This works fine. Now I'm struggling getting Svelte Material UI running.

After installing postcss, rollup-plugin-postcss, rollup-plugin-sass, svelte-material-uiand svelte-preprocess-sass and reading through here and there and there I added this to the plugins array in rollup.config.js:

postcss({
  extract: true,
  minimize: true,
  use: [
    ['sass', {
      includePaths: [
        './src/theme',
        './node_modules'
      ]
    }]
  ]
})

When I test it in my app using a @smui/button the button (with a default styling and the default ripple effect) works, but none of my SCSS gets compiled (or get overwritten during bundling).

I'm searching the needle in the haystack and appreciate any hint.

Answer 1

Got it, I just missed adding emitCss: true in the Svelte plugin config. So my working rollup.config.js is this:

export default {
    input: 'src/main.ts',
    output: {
        sourcemap: true,
        format: 'iife',
        name: 'myapp',
        file: 'public/build/bundle.js'
    },
    plugins: [
        svelte({
            // enable run-time checks when not in production
            dev: !production,
            // we'll extract any component CSS out into
            // a separate file - better for performance
            css: css => {
                css.write('bundle.css');
            },
            emitCss: true,
            preprocess: autoPreprocess()
        }),

        // If you have external dependencies installed from
        // npm, you'll most likely need these plugins. In
        // some cases you'll need additional configuration -
        // consult the documentation for details:
        // https://github.com/rollup/plugins/tree/master/packages/commonjs
        resolve({
            browser: true,
            dedupe: ['svelte']
        }),
        commonjs(),
        typescript({ sourceMap: !production }),

        // In dev mode, call `npm run start` once
        // the bundle has been generated
        !production && serve(),

        // Watch the `public` directory and refresh the
        // browser on changes when not in production
        !production && livereload('public'),

        // If we're building for production (npm run build
        // instead of npm run dev), minify
        production && terser()
    ],
    watch: {
        clearScreen: false
    }
};

This also has been answered here.