title: component selector is not a known element
body: <p>I have 2 modules <code>AppModule</code> and <code>MyArtModule</code> with some components declared in it.</p>
  
  <p>when I tried to use <code>ConfirmComponent</code> selector in <code>GraphicsComponent</code> it's working fine, but when I tried to use <code>ConfirmComponent</code> selector in <code>MyArtComponent</code> it's throwing an error <code>'artifi-confirm-alert' is not a known element:</code></p>
  
  <blockquote>
    <p>'artifi-confirm-alert' is not a known element:</p>
    
    <ol>
    <li><p>If 'artifi-confirm-alert' is an Angular component, then verify that it is part of this module.</p></li>
    <li><p>If 'artifi-confirm-alert' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component
    to suppress this message.</p></li>
    </ol>
  </blockquote>
  
  <ul>
  <li>AppModule
  
  <ul>
  <li>GraphicsComponent</li>
  <li>ConfirmComponent</li>
  <li>MyArtModule
  
  <ul>
  <li>MyArtComponent</li>
  </ul></li>
  </ul></li>
  </ul>
  
  <hr>
  
  <p>AppModule Code</p>
  
  <pre><code>@NgModule({
    declarations: [
      GraphicsComponent,
      ConfirmAlertComponent
    ],
    imports: [
      BrowserModule,
      MyArtModule
    ],
    ...
  })
  </code></pre>
  
  <hr>
  
  <p>MyArtModule Code</p>
  
  <pre><code>@NgModule({
    declarations: [
      MyArtComponent,
    ],
    imports: [
      CommonModule
    ],
    providers: [
      MyArtService
    ],
    exports: [
      MyArtComponent
    ]
  })
  </code></pre>
  
  <hr>
  
  <p><strong>replicated issue code</strong> - <a href="https://stackblitz.com/edit/skdroid-childmodule-in-child-component" rel="nofollow noreferrer">https://stackblitz.com/edit/skdroid-childmodule-in-child-component</a></p>
  
  <p>I've created <code>OneModule</code> with <code>OneComponent</code> and <code>TwoModule</code> with <code>TwoComponent</code>.</p>
  
  <p><code>&lt;app-one&gt;&lt;/app-one&gt;</code> and <code>&lt;app-two&gt;&lt;/app-two&gt;</code> are accessible in AppComponent.</p>
  
  <p>but unable to access <code>&lt;app-two&gt;&lt;/app-two&gt;</code> in AppOne component.</p>