title: Upgrading Angular 8 to Angular 9 Error: .ts is missing from the TypeScript compilation
body: <p>I recently upgraded out Angular 8 application, to Angular 9, using the following commands:</p>
  
  <pre><code>ng update @angular/core@8 @angular/cli@8
  ng update @angular/core @angular/cli
  </code></pre>
  
  <p>The only package that manually needed changes, was <code>ngx-store</code> to <code>ngx-store-9</code>, which I did with the following commands:</p>
  
  <pre><code>npm uninstall ngx-store
  npm install ngx-store-9
  </code></pre>
  
  <p>I then went ahead and changed all of the import statements for <code>ngx-store</code> to <code>ngx-store-9</code>.</p>
  
  <p>I am now receiving the following error when I build my app:</p>
  
  <blockquote>
    <p>ERROR in ./src/app/models/companySearchCriteria.ts
    Module build failed (from ./node_modules/@ngtools/webpack/src/index.js):
    Error: D:_lieben\DevOps\Gtrack Web v3\GTrack.UI\Gtrack\src\app\models\companySearchCriteria.ts is missing from the TypeScript compilation. Please make sure it is in your tsconfig via the 'files' or 'include' property.
        at AngularCompilerPlugin.getCompiledFile (D:_lieben\DevOps\Gtrack Web v3\GTrack.UI\Gtrack\node_modules@ngtools\webpack\src\angular_compiler_plugin.js:933:23)
        at D:_lieben\DevOps\Gtrack Web v3\GTrack.UI\Gtrack\node_modules@ngtools\webpack\src\loader.js:41:31
        at processTicksAndRejections (internal/process/task_queues.js:93:5)</p>
  </blockquote>
  
  <p>Below, is my <code>tsconfig.app.json</code> file:</p>
  
  <pre><code>      "extends": "../tsconfig.json",
    "compilerOptions": {
      "outDir": "../out-tsc/app",
      "types": []
    },
    "files": [
      "main.ts",
      "polyfills.ts"
    ],
    "include": [
      "src/**/*.d.ts"
    ]
  }
  </code></pre>
  
  <p>I am not quite sure why this is happening. Any help would be appreciated.</p>