bug: rollup inlines external dependency because import path was re-written

Type of Issue

• Bug Report
• Feature Request

Description

FESM bundles include inlined external dependencies.

How To Reproduce

Exmaple w/ ngx-translate:

The ng-package.json:

{
    "$schema": "../../node_modules/ng-packagr/lib/ng-package.schema.json",
    "lib": {
        "entryFile": "public_api.ts",
        "externals": {
            "@ngx-translate/core": "ngx-translate-core"
        }
    }
}

The source code:

import { TranslateService } from '@ngx-translate/core';

export class MyLib {
  // do stuff with TranslateService
}

In the .ng_build directory, the generated .js file ends up with the following import:

import { TranslateModule, TranslateLoader } from '@ngx-translate/core/index';

The import path from @ngx-translate/core in the source was re-written to @ngx-translate/core/index, thus the externals mapping does not match and rollup inlines the third-party dependency.

---

To confirm the cause, the following setting then produces a good FESM bundle!

{
    "lib": {
        "entryFile": "public_api.ts",
        "externals": {
            "@ngx-translate/core": "ngx-translate-core",
            "@ngx-translate/core/index": "ngx-translate-core"
        }
    }
}

FESM Bundle:

import { TranslateLoader, TranslateModule } from '@ngx-translate/core/index';

Expected Behaviour

Externals dependencies shouldn’t be rewritten.

Usage of lib.externals in ng-package.json SHOULD BE the TypeScript import path from sources! In above examples: @ngx-translate/core.

Version Information

ng-packagr: v1.0.0-pre.14
node: v8.1.1
@angular: v4.3.3
@ngx-translate/core: v7.1.0
rxjs: 5.4.2
zone.js: 0.8.16

[dherges]

Sorry. I stopped one step short:

$ cd dist && yarn link && cd ..
$ yarn link "ngx-codemirror"
$ yarn build
ERROR in ./dist/ngx-codemirror/ngx-codemirror.es5.js
Module not found: Error: Can't resolve 'codemirror/index' in '~/github/ngx-codemirror/dist/ngx-codemirror'
resolve 'codemirror/index' in '~/github/ngx-codemirror/dist/ngx-codemirror'
  Parsed request is a module
  using description file: ~github/ngx-codemirror/dist/package.json (relative path: ./ngx-codemirror)
    Field 'browser' doesn't contain a valid alias configuration
  after using description file: ~github/ngx-codemirror/dist/package.json (relative path: ./ngx-codemirror)
    resolve as module

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