Typescript: Object detection for "Exported variable `` has or is using name `` from external module"

[Deathspike]

With the following structure:

• node_modules/a/default.d.ts containing a typing and a function
• node_modules/a/package.json containing a typings field to default.d.ts
• src/default.ts' re-exporting everything from a and exporting new functions
• src/newFunctions.ts using the src/default.ts

You get "exported variable has or is using name from external module" errors when using an object:

import * as b from './default';

// Bug: This does the same thing, but in an object. It should still compile fine, but it doesn't.
export let wrap = {
  findPersonById: function(id: number): b.IPerson {
    return b.findPersonById(id);
  }
}

However, when you don't use an object the functionality works as expected:

import * as b from './default';

// OK: Expected behavior. Since `b` exports everything from `a`, exporting `b.IPerson` is fine.
export function wrapFindPersonById(id: number): b.IPerson {
  return b.findPersonById(123);
}

Using 1.8.0-dev.20151204. Full repo https://github.com/Deathspike/typescript-reference-bug-example/

[mhegazy]

A simplified repro is available in https://github.com/Microsoft/TypeScript/issues/8612

[robyoder]

8612 is what I'm trying to do. What is the difficulty of fixing this issue? Or, is there any way to work around this so that all the exports from a group of files can be imported into the same namespace?

[robyoder]

Aha. All I have to do is reference the original file, even if I don't use that reference. So, before, I had this:

////// model/index.ts

export { Team } from './Team'
export { Game } from './Game'
export { Score } from './Score'

////// action/index.ts

import * as model from '../model'

// This declaration produces the "cannot be named" error
export const getTeam = (teamId: string): model.Team => {
    // ...
}

But if I add import * as __Team from '../model/Team' to action/index.ts I'm error-free:

////// action/index.ts

import * as model from '../model'
import * as __Team from '../model/Team' // Throwaway reference

// No more error!
export const getTeam = (teamId: string): model.Team => {
    // ...
}

It's less than ideal, but at least I can keep my model.Team format.

[MaxLi1994]

if setting compilerOptions.declaration to false, there will be no more error!

[robyoder]

Right... but that's not what we want. It should work fine whether we generate declaration files or not. In my case, I need the declaration files to be generated, and this workaround has proven successful, but quite the pain.

[alex-okrushko]

Any ETA on this? Thanks!

[atrauzzi]

Would love to see this one addressed, a bit pesky.

[axefrog]

At the very least, as a shorter-term solution, it'd be nice to see a compiler option that allows definition files to be generated, with definitions that "cannot be named" simply being omitted, or replaced with any. I want definition files, but I find it annoying that one my two co-dependent projects keeps insisting that the definitions in the other can't be named, like some kind of low-ranking bureaucrat who refuses to think beyond the literal wording in his employee manual.

[baio]

I've just started to move shared code from your /shared project folder to separate module and stuck with this issue. Very sad !

[robyoder]

In case you missed it, there is a workaround to this issue if you're stuck. I posted it above.

[theigor]

@robyoder - I'm running into this same issue but with a module that's not mine. Specifically - express.

import * as express from "express";

let router = express.Router();

router.use(...);

export = router;

recreates this issue for router but I can't simply say import * as Router from "express/Router" because that doesn't exist. Is there a different workaround for this case or am I doing something wrong?

Thanks!

[theigor]

Oh and I found a solution here - https://github.com/Microsoft/TypeScript/issues/9944#issuecomment-288776200

[robyoder]

@theigor right, that's the solution. You could still use it as express.Router() though. All TS needs is the name to be imported. So you'd just add

import { Router } from "express";

but you don't actually need to change any other code (to use Router directly).

[robyoder]

@weswigham your fix is good for explicit re-exports like this:

export { Team } from "./Team";

but TS still fails when using a star export like this:

export * from "./Team";

I've pushed a simple project showing this issue: https://github.com/robyoder/tsctest

[weswigham]

@robyoder Wanna open a new issue with the new repro? The reason for that failure is different from the underlying reason the named reexports were failing.

[robyoder]

@weswigham done: #20657