Module Augmentation fails when exports are declared in an ExportClause

[EvanCahill]

TypeScript Version:

nightly (1.9.0-dev.20160502)

Code

// ext1.d.ts
declare module "State" {
    interface IState {
        num: number;
    }
    export { IState };
}

// ext2.d.ts
declare module "State" {
    interface IState {
        str: string;
    }
    export { IState };
}

//app.ts
import { IState } from "State";

function test(state: IState): void {
    console.log(state.num);
    console.log(state.str);
}

// tsconfig.json
{
    "files": [
        "app.ts",
        "ext1.d.ts",
        "ext2.d.ts"
    ]
}

Expected behavior:
The "State" module and IState interface declarations should be merged and the code should compile without errors.

Actual behavior:
The declaration files report error TS2300: Duplicate identifier 'IState'

Workaround:
The above errors do not occur when both IState interfaces are exported inline using the export modifier instead of in a ExportClause.
NOTE: If the first is exported inline and the second is exported in an ExportClause then the second declaration errors with TS2482: Export declaration conflicts with exported declaration of 'IState'.

[mhegazy]

The behavior is what i would expect. the error message could be better.

also note, you do not need the export modifier. all declarations are implicitly exported in an ambient context. so this is is semantically equivalent to your sample:

// ext2.d.ts
declare module "State" {
    interface IState {
        str: string;
    }
}

[EvanCahill]

If the two are semantically equivalent then why does the the former producer errors while the later does not? That is, if both interface declarations omit the export and are implicitly exported instead then the code compiles.

With regards to the use of the export keyword I included it as that is how the declarations are generated by the compiler when compiling with --module system|amd, --outFile and --declaration. For a little more context on the problem I have 3 projects all setup with the above compiler options. The first two projects both have a State.ts file which declare the IState interface. The third project consumes the other two. If I export the IState interface in both places using an inline export then everything compiles and works as desired. If instead I export them in an ExportClause then I get the duplicate identifier errors.

[Denis535]

It seems I also stumbled on this problem.

import gulp = require("gulp"); // import declaration conflicts with local declaration of gulp

gulp["devTask"] = function () {
    if (process.env.NODE_ENV !== 'production') return gulp.task.apply(this, arguments);
}

module gulp {
    interface Gulp {
        devTask(name: string): void;
    }
}

I don't understand is this error a bug or not?
If not, why I can merge interfaces in my modules, but can't merge with not mine module?
What does Domain: Error Messages mean? As I understand you just want to replace error text?

[mhegazy]

looking at this again, this is the same issue as #8140.

[mhegazy]

closing in favor of #8140.

[Denis535]

All the same I don't understand. Should it work or not?
Now I changed variable name:

import _gulp = require("gulp");

_gulp["devTask"] = function () {
    if (process.env.NODE_ENV !== 'production') return _gulp.task.apply(this, arguments);
}

declare module gulp {
    interface Gulp {
        devTask(name: string): void;
    }
}

Now there is no errors, but _gulp still hasn't my function.

[mhegazy]

All the same I don't understand. Should it work or not?

I think it should not work, and it should be an error. currently it is not an error, but it does not work as expected.

Now there is no errors, but _gulp still hasn't my function.

you should use module augmentation instead:

import gulp = require("gulp");

// augment the module
declare module "gulp" {
    interface Gulp {
        devTask(name: string): void;
    }
}

gulp.devTask = function () {
    if (process.env.NODE_ENV !== 'production') return gulp.task.apply(this, arguments);
}

[Denis535]

You code throws an error.
declare module "gulp" { // duplicate identifier ' "gulp" '

[mhegazy]

what version of TS are you using?

[Denis535]

Typescript for Microsoft Visual Studio 1.8.29.0.

[mhegazy]

looks like you are running into #7545, which has been fixed after 1.8.

[Denis535]

What is the last version?
On npm I see 1.8.10. On this repository I see 1.9.0.
Here is https://www.microsoft.com/en-us/download/details.aspx?id=48593 even version 1.8.6.0 (But my currently installed one is 1.8.29.0).
In C:\Program Files (x86)\Microsoft SDKs\TypeScript\1.8\ tsc version 1.8.9.

Is there a way to get version of TypeScript used for compiling? Because I'm not sure what TS version VS is using.

[mhegazy]

tsc --v

What is available currently is the nightly builds (npm install typescript@next).

[Denis535]

tsc --v

I mean something kind of
console.log( TypeScript.version );
Because I'm not sure which the TS is used (npm loca, global, Microsoft SDKs).

Ok, I installed typescript@next. And read this https://github.com/Microsoft/TypeScript/wiki/Dev-Mode-in-Visual-Studio
Do I really must to edit the registry? Why not make just TS path option in Visual Studio?

[mhegazy]

VS stores options in the registry as well :)

[shaunluttin]

We're seeing a similar error. After doing npm install ag-grid --save, we tried to augment the module as follows.

// augmentation.d.ts
import agGrid = require("ag-grid");

declare module "ag-grid" {
    interface ColDef {
        str: string;
    }
}

On build with tsc 2.4.1 we see the following error:

node_modules/ag-grid/main.d.ts(135,10): error TS2484: Export declaration conflicts with exported declaration of 'ColDef'.

We have also tried this approach:

// augmentation.d.ts
declare module "ag-grid" {
    interface ColDef {
        str: string;
    }
}

In that case, the actual behavior is that the ColDef interface now has only the str property.

// index.ts
import { ColDef } from "ag-grid";

let def: ColDef;