Does not unwrap default exports in CJS under default property

[enisdenjo]

Problem

Various transpilers (like TypeScript) put default exports under the default property when transpiling ESM to CJS.

Meaning:

// mylib (source es)
export default function foo() {};

becomes (roughly):

// mylib (transpiled cjs)
Object.defineProperty(exports, "__esModule", { value: true });
exports.default = foo;
function foo() {};

When consuming such modules, transpilers add "unwrap" helpers (like tslib.__importDefault in TypeScript) to detect the __esModule property in exports and use the default property.

In essence, importing mylib from above like this:

// (source es)
import foo from 'mylib';

will produce the following output (roughly) in TypeScript:

// (transpiled cjs)
const tslib = require('tslib');
const foo = tslib.__importDefault(require('mylib'));

This is not the case with pkgroll, it'll consume mylib without any helpers or checks during bundling.

Please consult the attached repro repository as well as the failing CI showcasing the issue.

Expected behavior

pkgroll uses helpers or detects such cases during bundling to create outputs that handle such cases.

Minimal reproduction URL

https://github.com/enisdenjo/pkgroll-cjs-default-exports-unwrap

Version

v2.5.1

Node.js version

v22.11.0

Package manager

npm

Operating system

macOS

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