title: Cannot generate library. Invalid rule result: Instance of class Promise
body: <p>when running <code>ng generate library mylib</code></p>
  
  <p>i get the following error:</p>
  
  <blockquote>
    <p>Invalid rule result: Instance of class Promise.</p>
  </blockquote>
  
  <p>I'm thinking its a package issue but i don't know how to find which one is causing the problem. </p>
  
  <p>Heres my package.json</p>
  
  <pre><code>{
    "dependencies": {
      "@angular/animations": "~7.2.12",
      "@angular/cdk": "^7.3.7",
      "@angular/common": "~7.2.12",
      "@angular/compiler": "~7.2.12",
      "@angular/core": "~7.2.12",
      "@angular/flex-layout": "^7.0.0-beta.23",
      "@angular/forms": "~7.2.12",
      "@angular/material": "^7.3.7",
      "@angular/platform-browser": "~7.2.12",
      "@angular/platform-browser-dynamic": "~7.2.12",
      "@angular/router": "~7.2.12",
      "core-js": "^2.5.4",
      "hammerjs": "^2.0.8",
      "ngx-infinite-scroll": "^7.1.0",
      "oidc-client": "~1.6.1",
      "rxjs": "~6.4.0",
      "tslib": "^1.9.0",
      "zone.js": "~0.8.26",
      "@nrwl/angular": "^8.1.2"
    },
    "devDependencies": {
      "@angular-devkit/build-angular": "~0.13.0",
      "@angular/cli": "^7.3.8",
      "@angular/compiler-cli": "~7.2.12",
      "@angular/language-service": "~7.2.12",
      "@nrwl/workspace": "8.1.2",
      "@types/jasmine": "~2.8.8",
      "@types/jasminewd2": "~2.0.3",
      "@types/node": "~8.9.4",
      "codelyzer": "~5.0.1",
      "dotenv": "6.2.0",
      "jasmine-core": "~2.99.1",
      "jasmine-spec-reporter": "~4.2.1",
      "karma": "~4.0.1",
      "karma-chrome-launcher": "~2.2.0",
      "karma-coverage-istanbul-reporter": "~2.0.1",
      "karma-jasmine": "~1.1.2",
      "karma-jasmine-html-reporter": "^0.2.2",
      "ts-node": "~7.0.0",
      "tslint": "~5.11.0",
      "typescript": "^3.2.4"
    }
  }
  </code></pre>
  
  <p>npm version 6.9.0</p>
  
  <p>node version 10.16.0</p>
  
  <p>Let me know if you need anything else. Thanks!</p>