[Bug]: Babel with Typescript produces functions for an empty namespaces.

[qisoft]

💻

• Would you like to work on a fix?

How are you using Babel?

babel-loader (webpack)

Input code

export namespace A {}
export namespace B {
    interface C {} 
}

Configuration file name

.babelrc

Configuration

{
    "presets": [
        [
            "@babel/preset-env",
            {
                "modules": false
            }
        ],
        [
            "@babel/preset-typescript",
            {
                "allowNamespaces": true
            }
        ]
    ]
}

Current and expected behavior

Current behavior:
Babel produces consts and empty functions for these namespaces.

Expected behavior:
Babel should ignore them the same way as TypeScript compiler does.

This is useful when you have a React component and a namespace with the same name containing the Props interface inside. This allows you to import { ComponentName } from './ComponentName' without additional import for Props type by accessing it with ComponentName.Props. Such namespace exists in types scope only and should not affect the resulting code. There is no sense and use of such function produced from these empty namespaces, it's just garbage.

Environment

• Babel version: 7.19.1
• Node version: 16

Possible solution

No response

Additional context

No response

[babel-bot]

Hey @qisoft! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite.

[qisoft]

PS: I know that I can use declare namespace { ... } instead of just namespace but this doesn't work for the nested namespace (e.g.

export namespace A {
  export declare namespace B {
    export interface C { }
  }
}

It still produces an empty function for B inside A:

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.A = void 0;
let A;
exports.A = A;

(function (_A) {
  let B;

  (function (_B) {})(B || (B = _A.B || (_A.B = {})));
})(A || (exports.A = A = {}));