es2015 re-export module and override single export function of the re-exported module

Question

I want to re-export a whole module and override only a specific function of the re-exported module. But it seems exporting the override function doesn't get processed when the same function is already re-rexported.

(http://www.ecma-international.org/ecma-262/6.0/#sec-module-semantics-static-semantics-early-errors, 'It is a Syntax Error if the ExportedNames of ModuleItemList contains any duplicate entries.')

The motivation behind my approach is to minimize explicit re-exporting a very big or long module, if I only want to override a specific function or method in the re-exported module.

Is there any way to implement my approach in es6/es2015?

My code so far:

module-a.js

export class MyFirstStandardClass {
  sendMeMessages() {
  return `hello, I'm a standard implementation`;
  }
}
export function talkToMe() {
  return `standard talking: how are you doing?`;
}

module-b.js

import * as StandardModule from 'module-a';

export function talkToMe(condition = true) {
  if (condition) {
    return `project conditional talking: ${StandardModule.talkToMe()}`;
  }
  return `project without a condition!`;
}

export * from 'module-a';

module-c.js

import * as MyModule from 'module-b';
import React, { Component } from 'react';

export default class App extends Component {

  componentWillMount() {
    console.log(MyModule);
    this.myFirstStandardInstance = new MyModule.MyFirstStandardClass();
  }

  render() {
    return (
      <div>
        <label>
          Class
        </label>
        <div>
          { this.myFirstStandardInstance.sendMeMessages() }
        </div>
        <label>
          Function
        </label>
        <div>
          { MyModule.talkToMe(true) } // returns 'standard talking: how are you doing?'; expected 'project conditional talking: standard talking: how are you doing?' 
        </div>
      </div>
    );
  }
}

Answer 1

It seems my first solution should work. According to the ECMAScript spec local exports should have priority. (http://www.ecma-international.org/ecma-262/6.0/#sec-getexportednames)

It's an issue in the Babel transpiler. More info: https://github.com/systemjs/systemjs/issues/1031#issuecomment-171262430

Issue in Babel: https://phabricator.babeljs.io/T6967

Answer 2

You can select which modules from module-a to export on one line. So in your module-b.js you can do:

// export all modules excluding `talkToMe`
export { MyFirstStandardClass, someOtherModule } from 'module-a';

export function talkToMe(condition = true) {
    // ...
}

Or you can export default object and choose what to exclude/override with Object.assign():

import * as StandardModule from 'module-a';

const overridenExports = {
    talkToMe: function(condition = true) {
        // ...
    }
}

const myModule = Object.assign({}, StandardModule, overridenExports);

export default myModule;

and import default like:

import MyModule from 'module-b';