Module augmentation with export list

[paleo]

TypeScript Version:

1.8.10

Code

// scale.ts
class Scale {
    weightOnEarth(mass) {}
}
export { Scale }

// advancedScale.ts
import {Scale} from "./scale" ;

declare module "./scale" {
  interface Scale {
    weightOnMoon(mass);
  }
}
Scale.prototype.weightOnMoon = function (ee) {
}

// consumer.ts
import { Scale } from "./scale";
import "./advancedScale";

let scale: Scale;
scale.weightOnMoon(10);  // ok
scale.weightOnEarth(10);

// tsconfig.json
{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5"
  }
}

Bug 1

This code is from this post, with just a small change: in scale.ts, the syntax of export list is used export { Scale }.

The compiler returns errors:

scale.ts(5,10): error TS2484: Export declaration conflicts with exported declaration of 'Scale'
advancedScale.ts(9,1): error TS2304: Cannot find name 'Scale'.
consumer.ts(7,7): error TS2339: Property 'weightOnEarth' does not exist on type 'Scale'.

Bug 2

With the original code, in consumer.ts, the line import "./advancedScale"; can be removed but the code still compiles.

[mhegazy]

Issue 2, is expected, since you have a tsconfig.json with no "files" or "exclude" list, and that tells the compiler to include all files. so the file is included whether you import it or not.

issue 1 is the real problem here. the work around is to export the declaration and not use an export statement:

// scale.ts
export class Scale {
    weightOnEarth(mass) {}
}