rollup.config.mjs

import fs from 'node:fs/promises';

import terser from '@rollup/plugin-terser';
import typescript from '@rollup/plugin-typescript';
import { dts } from 'rollup-plugin-dts';

/**
 * @param {string} path
 * @returns {Promise<boolean>}
 */
async function pathExists(path) {
  try {
    await fs.access(path);
    return true;
  } catch (_err) {
    return false;
  }
}

const PACKAGE_JSON_PATH = './package.json';

if (!pathExists(PACKAGE_JSON_PATH)) {
  throw new Error(`Expected "${PACKAGE_JSON_PATH}" path to exist`);
}

const packageJsonObject = JSON.parse(await fs.readFile(PACKAGE_JSON_PATH));
const packageDependencies = Object.keys(packageJsonObject.dependencies ?? {});

/** @type {!import("rollup").MergedRollupOptions[]} */
export default [
  {
    input: './src/index.ts',
    external: packageDependencies,
    output: [
      {
        dir: './lib/esm',
        format: 'esm',
        sourcemap: true,
        sourcemapPathTransform: (relativeSourcePath) => {
          // Rollup seems to generate source maps pointing to the wrong directory. Ugly patch to fix it
          if (relativeSourcePath.startsWith('../')) {
            return relativeSourcePath.slice(3);
          } else {
            return relativeSourcePath;
          }
        },
      },
    ],
    plugins: [
      typescript({
        tsconfig: './tsconfig.esm.json',
      }),
      terser(),
    ],
  },
  {
    input: 'lib/esm/index.d.ts',
    output: [{ file: 'lib/esm/index.d.ts', format: 'es' }],
    plugins: [
      dts({
        tsconfig: './tsconfig.esm.json',
      }),
    ],
  },
];