Can't access default export properties when `moduleResolution: 'NodeNext'`

[Ifiok Jr.]

✨ Description

typescript@4.7.2 added ECMAScript support.

With the new setting activated, importing from this module doesn't recognize any of the properties available on the default export is.

Currently, is exports itself as a merged namespace and function.

declare function is(value: unknown): TypeName;
declare namespace is {
  export var undefined: (value: unknown) => value is undefined;
}

export default is;

This doesn't seem to recognize properties with the new setting active.

I think that changing to use an interface as the main export should maintain the current behaviour and fix backward compatibility issues.

declare interface Is {
  (value: unknown): TypeName;
  undefined: (value: unknown) => value is undefined;
}

declare const is: Is;
export default is;

I've also opened an issue in the TypeScript repo.

💻 Code

tsconfig.json

{
  "compilerOptions": {
    "module": "ESNext",
    "target": "ESNext",
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "moduleResolution": "NodeNext", // This is the added option
  }
}

Example

import is from '@sindresorhus/is';

is.nullOrUndefined('something');
// => Property 'nullOrUndefined' does not exist on type 'typeof import("file:///node_modules/@sindresorhus/is/dist/index")

is.emptyObject({});
// => Property 'emptyObject' does not exist on type 'typeof import("file:///node_modules/@sindresorhus/is/dist/index")'.

📦 Versions

• typescript - 4.7.2
• @sindresorhus/is - 4.6.0

[Ifiok Jr.]

It seems like this is a TypeScript issue, and the only way to currently fix it is to upgrade this package to support esm (type: module).

I'll keep it open since it might be useful for those who run into the same issue.

[Sindre Sorhus]

Can you try https://github.com/sindresorhus/is/releases/tag/v5.0.0?

[Ifiok Jr.]

Thanks @sindresorhus

The types are working in the playground now when the module is set to NodeNext.