rollup - How can I write CSS outside the JS destination folder

Question

Svelte uses Rollup for bundling. This is the folder structure.

svelte/
├── node_modules/
├── public/
│   ├── bundle.js
│   └── bundle.css
├── src/
│   ├── App.svelte
│   └── main.js
└── rollup.config.js

I want to save both the bundle.js and bundle.css outside the root folder.

Here's the rollup config.

input: "src/main.js",
    output: {
        format: "cjs",
        name: "app",
        file: "../../src/svelte/bundle.js",
    },
    plugins: [
        svelte({
            css: (css) => {
                css.write("/bundle.css");
            },
        }),
    ],

I can save the bundle.js fine, but the path passed to css.write() for bundle.css is relative to the bundle.js destination directory.

If I try to do css.write("../bundle.css") , I get this error...

Error: The "fileName" or "name" properties of emitted files must be strings that are neither absolute 
nor relative paths and do not contain invalid characters, received "/bundle-svelte-activities.css".

Answer 1

Here some snippets to make it happen:

...
import css from 'rollup-plugin-css-asset';

export default {
    input: 'src/main.js',
    output: {
        sourcemap: true,
        format: 'iife',
        name: 'app',
        assetFileNames: 'bundle.css',
        dir: 'public/build',
        entryFileNames: 'bundle.js'
    },
    plugins: [
       svelte({
            ...
            emitCss: true,
       }),
       ...
       css({   
           name: 'bundle',
       }),
       ...
     ],
     ...