rollup.config.mjs

import fs from "fs";
import path from "path";
import util from "util";
import { fileURLToPath } from "url";
import minimist from "minimist";

import typescript from "@rollup/plugin-typescript";
import { nodeResolve } from "@rollup/plugin-node-resolve";
import commonJs from "@rollup/plugin-commonjs";
import externals from "rollup-plugin-node-externals";

import { getPackages } from "@lerna/project";
import { filterPackages } from "@lerna/filter-packages";
import batchPackages from "@lerna/batch-packages";

// we need to change up how __dirname is used for ES6 purposes
const __dirname = path.dirname(fileURLToPath(import.meta.url));

/**
 * Get a list of the non-private sorted packages
 */
async function getSortedPackages(scope, ignore) {
	const packages = await getPackages(__dirname);
	const filtered = filterPackages(packages, scope, ignore, false);

	return batchPackages(filtered).reduce((arr, batch) => arr.concat(batch), []);
}

async function main() {
	// Support --scope and --ignore globs if passed in via commandline
	const { scope, ignore } = minimist(process.argv.slice(2));
	const packages = await getSortedPackages(scope, ignore);

	const configs = packages.map((pkg) => {
		// Absolute path to package directory
		const basePath = path.relative(__dirname, pkg.location);

		// "main" field from package.json file.
		const pkgJSON = pkg.toJSON();

		// Absolute path to input file
		const input = path.join(basePath, pkgJSON.input);

		// Skip rollup build if package has "build" configured.
		if (pkgJSON.scripts?.build) {
			console.log(pkgJSON.name, "has custom build! skipping rollup build.");
			return;
		}

		// Copy README.md and LICENSE into child package folder.
		if (!fs.existsSync(path.join(basePath, "README.md"))) {
			fs.copyFileSync(
				path.resolve(__dirname, "README.md"),
				path.join(basePath, "README.md"),
			);
			fs.copyFileSync(
				path.resolve(__dirname, "LICENSE"),
				path.join(basePath, "LICENSE"),
			);
		}

		const tsconfig = {
			rootDir: path.join(basePath),
			declarationDir: path.join(basePath, "build"),
			declaration: true,
			include: ["src/**/*.ts"],
		};

		//
		// Here's the individual rollup.config.js for each package
		// Uses two separate builds: one for CJS and other for ESM.
		//
		return [
			{
				input,
				preserveModules: true,
				output: [
					{ dir: path.join(basePath, "build"), format: "cjs", sourcemap: true },
				],
				plugins: [
					externals({
						deps: true,
						peerDeps: true,
						devDeps: true,
						packagePath: path.join(basePath, "package.json"),
					}),
					nodeResolve(),
					commonJs(),
					typescript({
						...tsconfig,
						module: "ESNext",
						target: "ESNext",
					}),
				],
			},
			{
				input,
				preserveModules: true,
				output: [
					{
						dir: path.join(basePath, "build"),
						format: "esm",
						entryFileNames: "[name].mjs",
						sourcemap: true,
					},
				],
				plugins: [
					externals({
						deps: true,
						peerDeps: true,
						devDeps: true,
						packagePath: path.join(basePath, "package.json"),
					}),
					nodeResolve(),
					commonJs(),
					typescript({
						...tsconfig,
						module: "ESNext",
						target: "ESNext",
					}),
				],
			},
		];
	});

	console.log("ROLLUP CONFIGS:", util.inspect(configs, false, Infinity, true));

	return configs.filter((c) => c !== undefined);
}

export default (await main()).flat();