Angular 6 / 7 “the result of a dependency is an expression”

Question

The main problem is not why you are getting that warnings. The way you are accessing the library is not an ideal way. Let’s look into a little better approach [Using Angular 7] with your own sample steps, which will not cause that issue in the first place.

Step 1: [Same as yours]

ng new workspace # accept the defaults
ng new product # accept the defaults
cd workspace 
ng generate library widgets 
ng build --prod widgets # leave out "--prod" for Angular 7
cd ../product
ng build

Step 2: Create .tgz library file

cd ../workspace/dist/widgets/
npm pack
cp widgets-0.0.1.tgz ../../../product/

Step 3: Add “widgets” library in package.json

Open package.json file of product project, and under devDependencies add the following line:

"widgets": "file:./widgets-0.0.1.tgz",

Step 2 and Step 3 are required if you have the library locally. Otherwise, if your library is packed and publish into npm repository, then you don’t need file: keyword. You can just mention the version like other dependencies.

Step 4: Install newly added library

Run npm install in product project.

Step 5: Use the library

Modify app.module.ts file:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { WidgetsModule } from 'widgets'; // new line

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    WidgetsModule // new line
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Step 6: Build product project

Now, run ng build in product project. It will run successfully.

Angular Product Project Build