rollup.config.js

import fs from 'fs';
import replace from '@rollup/plugin-replace';
import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import json from '@rollup/plugin-json';
import sucrase from '@rollup/plugin-sucrase';
import typescript from '@rollup/plugin-typescript';
import pkg from './package.json';

const is_publish = !!process.env.PUBLISH;

const ts_plugin = is_publish
	? typescript({
		include: 'src/**',
		typescript: require('typescript')
	})
	: sucrase({
		transforms: ['typescript']
	});

const external = id => id.startsWith('svelte/');

fs.writeFileSync(`./compiler.d.ts`, `export { compile, parse, preprocess, walk, VERSION } from './types/compiler/index';`);

export default [
	/* runtime */
	{
		input: `src/runtime/index.ts`,
		output: [
			{
				file: `index.mjs`,
				format: 'esm',
				paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '.')}/index.mjs`
			},
			{
				file: `index.js`,
				format: 'cjs',
				paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '.')}/index.js`
			}
		],
		external,
		plugins: [ts_plugin]
	},

	{
		input: `src/runtime/ssr.ts`,
		output: [
			{
				file: `ssr.mjs`,
				format: 'esm',
				paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '.')}/index.mjs`
			},
			{
				file: `ssr.js`,
				format: 'cjs',
				paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '.')}/index.js`
			}
		],
		external,
		plugins: [ts_plugin]
	},

	...fs.readdirSync('src/runtime')
		.filter(dir => fs.statSync(`src/runtime/${dir}`).isDirectory())
		.map(dir => ({
			input: `src/runtime/${dir}/index.ts`,
			output: [
				{
					file: `${dir}/index.mjs`,
					format: 'esm',
					paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '..')}/index.mjs`
				},
				{
					file: `${dir}/index.js`,
					format: 'cjs',
					paths: id => id.startsWith('svelte/') && `${id.replace('svelte', '..')}/index.js`
				}
			],
			external,
			plugins: [
				replace({
					__VERSION__: pkg.version
				}),
				ts_plugin,
				{
					writeBundle(bundle) {
						if (dir === 'internal') {
							const mod = bundle['index.mjs'];
							if (mod) {
								fs.writeFileSync('src/compiler/compile/internal_exports.ts', `// This file is automatically generated\nexport default new Set(${JSON.stringify(mod.exports)});`);
							}
						}

						fs.writeFileSync(`${dir}/package.json`, JSON.stringify({
							main: './index',
							module: './index.mjs',
							types: './index.d.ts'
						}, null, '  '));

						fs.writeFileSync(`${dir}/index.d.ts`, `export * from '../types/runtime/${dir}/index';`);
					}
				}
			]
		})),

	/* compiler.js */
	{
		input: 'src/compiler/index.ts',
		plugins: [
			replace({
				__VERSION__: pkg.version,
				'process.env.NODE_DEBUG': false // appears inside the util package
			}),
			{
				resolveId(id) {
					// util is a built-in module in Node.js, but we want a self-contained compiler bundle
					// that also works in the browser, so we load its polyfill instead
					if (id === 'util') {
						return require.resolve('./node_modules/util'); // just 'utils' would resolve this to the built-in module
					}
				}
			},
			resolve(),
			commonjs({
				include: ['node_modules/**']
			}),
			json(),
			ts_plugin
		],
		output: [
			{
				file: 'compiler.js',
				format: is_publish ? 'umd' : 'cjs',
				name: 'svelte',
				sourcemap: true,
			},
			{
				file: 'compiler.mjs',
				format: 'esm',
				name: 'svelte',
				sourcemap: true,
			}
		],
		external: is_publish
			? []
			: id => id === 'acorn' || id === 'magic-string' || id.startsWith('css-tree')
	}
];