Types are not compatible with moduleResolution: "NodeNext"

[Starmarshal]

rollup-plugin-license@3.7.1 doesn't work with moduleResolution: "NodeNext".

With the usual import:

import rollupPluginLicense from 'rollup-plugin-license';

TypeScript resolves the CommonJS module as an object instead of a function, so calling the
plugin fails and the build breaks. The function can be reached with a manual .default
access, but that's not a safe workaround: depending on how the module is loaded, .default
is undefined at runtime (see
FalseExportDefault).

The reason is a mismatch between the types and the runtime:

• the package is CommonJS: "main": "dist/index.js", no exports field, no "type": "module";
• dist/index.js exports the plugin with module.exports = rollupPluginLicense;;
• dist/index.d.ts declares:

declare function rollupPluginLicense(options: Options): Plugin;

export default rollupPluginLicense;

For a CommonJS module, export default in the .d.ts describes module.exports.default,
which doesn't exist at runtime.
arethetypeswrong
confirms this - it reports "Incorrect default export" for all resolution kinds
(node10, node16 from CJS, node16 from ESM, bundler).

The types should use export = instead:

declare function rollupPluginLicense(options: Options): Plugin;

export = rollupPluginLicense;

One caveat: export = can't be combined with other export statements, so the exported
types (Options, Person, Dependency, ThirdParty, etc.) would need to be moved into
a declare namespace rollupPluginLicense block.

Would it be possible to fix this?

[madhav669]

Your diagnosis is right. I reproduced it with rollup-plugin-license@3.7.1 + TS module/moduleResolution: "NodeNext":

error TS2349: This expression is not callable.
  Type 'typeof import(".../rollup-plugin-license/dist/index")' has no call signatures.

One thing worth knowing though: rollup-plugin-license isn't part of this repo, it lives at mjeanroy/rollup-plugin-license (that's the repository in its package.json). I couldn't find an existing issue there for this, so opening one with the write-up above (the export = + declare namespace fix) is the way to get it fixed.

Until then, two workarounds that both type-check under NodeNext and call the real function at runtime (so no .default that's undefined):

1. Cast the default import (in ESM, the default import of a CJS module is module.exports, i.e. the function itself; only the types are wrong):

import licenseCjs from 'rollup-plugin-license';

// Types claim a `default` export; at runtime the import *is* the function.
const license = licenseCjs as unknown as typeof licenseCjs.default;

2. Load it with createRequire (useful if you'd rather not lean on ESM/CJS interop):

import { createRequire } from 'node:module';
import type licenseModule from 'rollup-plugin-license';

const license: typeof licenseModule.default =
  createRequire(import.meta.url)('rollup-plugin-license');

Both give you a fully typed license(options). Once the types switch to export =, the plain import license from 'rollup-plugin-license' will work and you can drop the workaround.