Default import from an ESM package into a CommonJS project with esModuleInterop is faulty

[JonasDoe]

🔎 Search Terms

"cjs esm esModuleInterop default", "common esm esModuleInterop default"

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about default imports from ESM to CommonJS
• I'm using TypeScript 5.4.5

⏯ Playground Link

https://github.com/JonasDoe/typescript-esm-issue

💻 Code

With esModuleInterop=true:

import { default as Provider } from 'oidc-provider'; // this is an ESM project with export default class Provider
console.log('Created new Provider:', new Provider('http://example.tld'))

The transpiled code will be:

"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
const oidc_provider_1 = __importDefault(require("oidc-provider"));
console.log('Created new Provider:', new oidc_provider_1.default('http://example.tld'));

🙁 Actual behavior

• Create a CommonJS project with Node22, so --experimental-require-module is supported.
• Import the default export of an ESM dependency
• Enable esModuleInterop
• Transpilation will create an object like {"default": {"default": the-imported-object}}, so the-imported-object isn't found

🙂 Expected behavior

• Transpilation should create an object like {"default": the-imported-object}, so without the double nesting.

Additional information about the issue

The original suggestion that this is a bug in TypeScript came from here: panva/node-oidc-provider#1249 (reply in thread), and by a person with greater knowledge about Node and TypeScript. So I'm sorry if I left something unclear.

[RyanCavanaugh]

esModuleInterop depends on the __esModule property in order to work, but Node's --experimental-require-module doesn't generate that. See nodejs/node#52697

[RyanCavanaugh]

Also nodejs/node#52166

Once that experimental feature lands (unexperimentally) in Node, you'll need to a) update to a version of TypeScript, which will eventually exist, that supports it and b) set module: nodenext in tsconfig

[JonasDoe]

I see! Thank you for the reponse!