Node.js Package Authors: Please support both CJS and ESM: https://dev.to/endel/nodejs-package-authors-please-support-both-cjs-and-esm-1oj3

README.md

Alternatively, use esbuild and tsc through the CLI to generate both CJS and ESM outputs: https://dev.to/endel/nodejs-package-authors-please-support-both-cjs-and-esm-1oj3

compile-packages.mjs

import fs from 'fs';
import path from 'path';
import glob from 'fast-glob';
import { fileURLToPath } from 'url';
import minimist from 'minimist';
import ts from "typescript";

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

import esbuild from "esbuild";

// 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 argv = minimist(process.argv.slice(2));
  console.log("ARGV:", argv);

  const packages = await getSortedPackages(argv.scope, argv.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();

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

    // Get all .ts as input files
    const entryPoints = glob.sync(path.resolve(basePath, "src", "**", "**.ts")
      .replace(/\\/g, '/')); // windows support

    const outdir = path.join(basePath, 'build');

    // Emit only .d.ts files
    const emitTSDeclaration = () => {
      console.log("Generating .d.ts files for...", pkgJSON.name);
      const program = ts.createProgram(entryPoints, {
        declaration: true,
        emitDeclarationOnly: true,
        skipLibCheck: true,
        module: "commonjs",
        target: "es2015",
        outDir: outdir,
        downlevelIteration: true, // (redis-driver)
        esModuleInterop: true,
        experimentalDecorators: true,
      });
      const emitResult = program.emit();

      const allDiagnostics = ts
        .getPreEmitDiagnostics(program)
        .concat(emitResult.diagnostics);

      allDiagnostics.forEach(diagnostic => {
        if (diagnostic.file) {
          const { line, character } = ts.getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start);
          const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, "\n");
          console.log(`${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`);
        } else {
          console.log(ts.flattenDiagnosticMessageText(diagnostic.messageText, "\n"));
        }
      });
    }

    // CommonJS output
    esbuild.build({
      entryPoints,
      outdir,
      format: "cjs",
      sourcemap: "external",
      platform: "node",
      watch: argv.watch,
    });

    // ESM output
    esbuild.build({
      entryPoints,
      outdir,
      format: "esm",
      sourcemap: "external",
      platform: "node",
      outExtension: { '.js': '.mjs', },
      watch: argv.watch && {
        onRebuild(err, result) {
          if (err) { return console.error(err); }
          // re-emit .d.ts files
          emitTSDeclaration();
        }
      },
    });

    // emit .d.ts files
    emitTSDeclaration();
  });
}

export default await main();