Allow augmentation of re-exported module

[christianacca]

I've sadly discovered that it not possible to augment a ES2015 module that is being re-exported. At least not without specifying the full path to the ES2015 that is then being re-exported.

This has significant implications, particularly for library authors and consumers.

An example would probably help clarify.

Suppose as an authored of a library I want to expose a simple surface area from which consumers should import from. I do this by creating an index.ts file that re-exports modules from nested sub-folders like so:

// index.ts
export { AClass } from './path/to/class-a';
export { BClass } from './path/to/class-b';
export { CClass } from './path/to/class-c';

Now a consumer can import like so:

import { AClass, BClass } from 'some-library'; 

The benefits of the above:

1. As library author I am free to reorganise the modules into sub-folders as the library code base grows without breaking consumers
2. As library consumer I don't need to have intimate knowledge of how the library organises it's file on disk - instead I have one path to import modules and this is the name of the npm package itself.

Once augmentation enters the picture all of the above benefits are now gone.

This is really bad for everyone.

What can be done about the situation?

Thanks
Christian

[christianacca]

Also, not being able to augment a re-exported module can cause confusion (eg: #11406) but does not necessarily have an obvious solution as per @RyanCavanaugh comment

[mhegazy]

so, is this your library? or a library you are using?

one thing to note, ES2015 does not allow augmenting on the top level of a module anyways. so moving forward the only augmentation allowed at runtime is augmenting export shapes themselves.

[christianacca]

Hi @mhegazy thanks for the quick reply.

Let's suppose this is a library I'm using that's been authored by someone else.

In reality, I hit this issue whilst writing a demo app of a library that I'm authoring. I spent 2 hours banging my head thinking I was going crazy!

In my case I was trying to augment an interface re-exported from ng-table

[blakeembrey]

There was a similar discussion at #9532 (comment). The only workaround I'm aware of is to augment the specific module instead of the exported one but that has all the caveats you mentioned. E.g. declare module './path/to/class-a'.

[christianacca]

Yup that is the workaround, but not a particularly satisfying one.

It means the author loses the freedom to rearrange modules inside a package. The consumer also has to know the "internal" paths.

[doliver3]

I've hit the same problem. It is important to have a solution to this problem.

[endel]

I've just hit this problem too. I'd like to augment THREE module but it's not possible.

Tried many ways, without success, such as:

declare namespace THREE {
    export interface Object3D {/* augmentations */}
}

declare module 'three' {
    export interface Object3D {/* augmentations */}
}

declare module 'three/three-core' {
    export interface Object3D {/* augmentations */}
}

Any workaround for this would be appreciated!

[speigg]

Ah, this is why it's not working. I'm trying to do the same thing as @endel (augmenting a re-exported class from the package-scoped three module).

EDIT, this worked for me:

declare module 'three/three-core' {
    interface Object3D {/* augmentations */}
}

[speigg]

I keep running into this issue over again, forgetting that I can't augment re-exported modules. Would be great if this were fixed.