title: An unhandled exception occurred: Could not find the implementation for builder @angular-devkit/build-angular:dev-server
body: <p>I was trying to install ngb-tabset, and I got some error on angular-core, which accordingly I ran:</p>
  
  <pre><code>npm install -S @angular/material @angular/cdk @angular/animations
  
  npm uninstall @angular/core
  
  npm install -S @angular/core
  </code></pre>
  
  <p>But then I got some other error... for which I did <code>npm update</code>, then again few errors. I did:</p>
  
  <pre><code>rm -rf node_modules
  npm install
  </code></pre>
  
  <p>Then I started getting the below error.</p>
  
  <blockquote>
    <p>An unhandled exception occurred: Could not find the implementation for 
       builder @angular-devkit/build-angular:dev-server
       See "/tmp/ng-2tgkqg/angular-errors.log" for further details.</p>
  </blockquote>
  
  <p>I tried to do -</p>
  
  <pre><code>npm install --save-dev @angular-devkit/build-angular
  </code></pre>
  
  <p>but of no use.</p>
  
  <p>And my package.json is -</p>
  
  <pre><code>{
    "name": "@coreui/coreui-free-angular-admin-template",
    "version": "2.0.1",
    "description": "CoreUI Free Angular 2+ Admin Template",
    "author": {
      "name": "Łukasz Holeczek",
      "url": "http://holeczek.pl",
      "github": "https://github.com/mrholek",
      "twitter": "https://twitter.com/lukaszholeczek"
    },
    "contributors": [
      {
        "name": "Andrzej Kopański",
        "url": "https://github.com/xidedix"
      }
    ],
    "homepage": "https://coreui.io/angular",
    "copyright": "Copyright 2018 creativeLabs Łukasz Holeczek",
    "license": "MIT",
    "scripts": {
      "ng": "ng",
      "start": "ng serve",
      "build": "ng build --prod",
      "test": "ng test",
      "lint": "ng lint",
      "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
      "@agm/core": "^1.0.0-beta.5",
      "@angular/animations": "^6.1.10",
      "@angular/cdk": "^7.3.3",
      "@angular/common": "^6.1.10",
      "@angular/compiler": "^6.1.10",
      "@angular/core": "^6.1.10",
      "@angular/forms": "^6.1.10",
      "@angular/http": "^6.1.10",
      "@angular/material": "^7.3.3",
      "@angular/platform-browser": "^6.1.10",
      "@angular/platform-browser-dynamic": "^6.1.10",
      "@angular/router": "^6.1.10",
      "@coreui/angular": "^2.0.0-rc.1",
      "@coreui/coreui": "^2.0.20",
      "@coreui/coreui-plugin-chartjs-custom-tooltips": "^1.2.0",
      "@coreui/icons": "^0.3.0",
      "@ng-select/ng-select": "^2.16.0",
      "@progress/kendo-angular-buttons": "^4.0.0",
      "@progress/kendo-angular-dateinputs": "2 - 3",
      "@progress/kendo-angular-dropdowns": "2 - 3",
      "@progress/kendo-angular-excel-export": "1 - 2",
      "@progress/kendo-angular-grid": "^3.13.0",
      "@progress/kendo-angular-inputs": "2 - 4",
      "@progress/kendo-angular-intl": "^1.0.0",
      "@progress/kendo-angular-l10n": "^1.1.0",
      "@progress/kendo-angular-popup": "^2.0.0",
      "@progress/kendo-data-query": "^1.0.0",
      "@progress/kendo-drawing": "^1.0.0",
      "@progress/kendo-theme-default": "latest",
      "@syncfusion/ej2-angular-dropdowns": "^16.4.55",
      "@syncfusion/ej2-angular-grids": "^16.4.55",
      "@syncfusion/ej2-ng-dropdowns": "^16.2.50",
      "@types/jquery": "^3.3.29",
      "angular-confirmation-popover": "^4.2.0",
      "angular-neo4j": "^0.7.1",
      "angular2-bootstrap-switch": "^0.2.3",
      "angular2-countrypicker": "^1.0.0",
      "angular2-google-maps": "^0.17.0",
      "apriori": "^1.0.7",
      "bcryptjs": "^2.4.3",
      "bootstrap": "^4.0.0-beta.3",
      "chart.js": "^2.7.3",
      "core-js": "^2.6.5",
      "cors": "^2.8.5",
      "country-select-js": "^2.0.1",
      "crud-sdk": "0.0.30",
      "cryptr": "^4.0.2",
      "csv-writer": "^1.2.0",
      "express": "^4.16.4",
      "express-jwt": "^5.3.1",
      "express-session": "^1.15.6",
      "file-saver": "^2.0.1",
      "flag-icon-css": "^3.2.1",
      "font-awesome": "^4.7.0",
      "html2canvas": "^1.0.0-rc.3",
      "html2pdf.js": "^0.9.1",
      "jquery": "^3.4.0",
      "jspdf": "^1.5.3",
      "jspdf-autotable": "^3.1.1",
      "login-sdk": "0.0.3",
      "mkdirp": "^0.5.1",
      "moment": "^2.22.2",
      "mongodb": "^2.2.33",
      "mongoskin": "^2.0.3",
      "morgan": "^1.9.1",
      "multer": "^1.4.1",
      "mutationobserver-shim": "^0.3.2",
      "nemex-angular2-realtimegeolocation": "0.0.6",
      "ng-multiselect-dropdown": "^0.2.3",
      "ng2-charts": "^1.6.0",
      "ng2-opd-popup": "^1.1.21",
      "ng2-select": "^2.0.0",
      "ngx-accordion": "0.0.17",
      "ngx-bootstrap": "^3.3.0",
      "ngx-country-select": "^2.0.6",
      "ngx-horizontal-timeline": "0.0.5",
      "ngx-loading": "^3.0.1",
      "ngx-mat-select-search": "^1.5.3",
      "ngx-pagination": "^3.2.1",
      "ngx-perfect-scrollbar": "^6.3.1",
      "ngx-scrollbar": "^3.2.2",
      "ngx-select-dropdown": "^1.0.1",
      "ngx-smart-modal": "^7.1.1",
      "ngx-ui-switch": "^8.0.0",
      "nodemailer": "^5.0.0",
      "nodemon": "^1.19.1",
      "notification-sdk": "0.0.9",
      "pdfmake": "^0.1.57",
      "primeicons": "^1.0.0",
      "primeng": "^7.1.3",
      "q": "^1.5.1",
      "redis": "^2.8.0",
      "request": "^2.88.0",
      "request-promise": "^4.2.2",
      "request-promise-native": "^1.0.5",
      "restify": "^7.2.2",
      "rootpath": "^0.1.2",
      "rxjs": "^6.4.0",
      "rxjs-compat": "^6.0.0",
      "simple-line-icons": "^2.4.1",
      "tinyurl": "^1.1.2",
      "ts-helpers": "^1.1.2",
      "tsickle": "^0.33.0",
      "tslib": "^1.10.0",
      "venn.js": "^0.2.20",
      "web-animations-js": "^2.3.1",
      "zone.js": "^0.8.29"
    },
    "devDependencies": {
      "@angular-devkit/build-angular": "^0.7.5",
      "@angular/cli": "^6.2.7",
      "@angular/compiler-cli": "^6.1.10",
      "@angular/language-service": "^6.1.10",
      "@types/jasmine": "^2.8.9",
      "@types/jasminewd2": "^2.0.5",
      "@types/node": "^10.14.4",
      "body-parser": "^1.18.3",
      "codelyzer": "^4.5.0",
      "jasmine-core": "^3.2.1",
      "jasmine-spec-reporter": "^4.2.1",
      "karma": "^3.0.0",
      "karma-chrome-launcher": "^2.2.0",
      "karma-coverage-istanbul-reporter": "^2.0.4",
      "karma-jasmine": "^1.1.2",
      "karma-jasmine-html-reporter": "^1.3.1",
      "protractor": "^5.4.1",
      "ts-node": "^7.0.1",
      "tslint": "^5.11.0",
      "typescript": "^2.9.2"
    },
    "engines": {
      "node": "&gt;= 8.9.4",
      "npm": "&gt;= 5.6.0"
    }
  }
  </code></pre>
  
  <p>angular.json</p>
  
  <pre><code>{
    "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
    "version": 1,
    "newProjectRoot": "projects",
    "projects": {
      "ng": {
        "root": "",
        "sourceRoot": "src",
        "projectType": "application",
        "architect": {
          "build": {
            "builder": "@angular-devkit/build-angular:browser",
            "options": {
              "outputPath": "dist",
              "index": "src/index.html",
              "main": "src/main.ts",
              "tsConfig": "src/tsconfig.app.json",
              "polyfills": "src/polyfills.ts",
              "assets": [
                "src/assets"
              ],
              "styles": [
                "./node_modules/bootstrap/dist/css/bootstrap.css",
                "node_modules/bootstrap/dist/css/bootstrap.min.css",
                "./node_modules/ngx-bootstrap/datepicker/bs-datepicker.css",
                "node_modules/@coreui/icons/css/coreui-icons.css",
                "node_modules/flag-icon-css/css/flag-icon.css",
                "node_modules/font-awesome/css/font-awesome.css",
                "node_modules/simple-line-icons/css/simple-line-icons.css",
                "src/scss/style.scss",
                "./node_modules/ngx-ui-switch/ui-switch.component.css",
                "node_modules/ngx-smart-modal/ngx-smart-modal.scss"
              ],
              "stylePreprocessorOptions": {
                "includePaths": [
                  "./node_modules"
                ]
              },
              "scripts": [
                "node_modules/chart.js/dist/Chart.min.js"
              ]
            },
            "configurations": {
              "production": {
                "optimization": true,
                "outputHashing": "all",
                "sourceMap": false,
                "extractCss": true,
                "namedChunks": false,
                "aot": true,
                "extractLicenses": true,
                "vendorChunk": false,
                "buildOptimizer": true,
                "fileReplacements": [
                  {
                    "replace": "src/environments/environment.ts",
                    "with": "src/environments/environment.prod.ts"
                  }
                ]
              }
            }
          },
          "serve": {
            "builder": "@angular-devkit/build-angular:dev-server",
            "options": {
              "browserTarget": "ng:build"
            },
            "configurations": {
              "production": {
                "browserTarget": "ng:build:production"
              }
            }
          },
          "extract-i18n": {
            "builder": "@angular-devkit/build-angular:extract-i18n",
            "options": {
              "browserTarget": "ng:build"
            }
          },
          "test": {
            "builder": "@angular-devkit/build-angular:karma",
            "options": {
              "main": "src/test.ts",
              "karmaConfig": "./karma.conf.js",
              "polyfills": "src/polyfills.ts",
              "tsConfig": "src/tsconfig.spec.json",
              "scripts": [
                "node_modules/chart.js/dist/Chart.min.js"
              ],
              "styles": [
                "node_modules/bootstrap/dist/css/bootstrap.css",
                "./node_modules/ngx-bootstrap/datepicker/bs-datepicker.css",
                {
                  "input": "node_modules/@progress/kendo-theme-default/dist/all.css"
                },
                "node_modules/flag-icon-css/css/flag-icon.css",
                "node_modules/font-awesome/css/font-awesome.css",
                "node_modules/simple-line-icons/css/simple-line-icons.css",
                "src/scss/style.scss"
              ],
              "stylePreprocessorOptions": {
                "includePaths": [
                  "./node_modules"
                ]
              },
              "assets": [
                "src/assets",
                "src/favicon.ico"
              ]
            }
          },
          "lint": {
            "builder": "@angular-devkit/build-angular:tslint",
            "options": {
              "tsConfig": [
                "src/tsconfig.app.json",
                "src/tsconfig.spec.json"
              ],
              "exclude": [
                "**/node_modules/**"
              ]
            }
          }
        }
      },
      "ng-e2e": {
        "root": "",
        "sourceRoot": "",
        "projectType": "application",
        "architect": {
          "e2e": {
            "builder": "@angular-devkit/build-angular:protractor",
            "options": {
              "protractorConfig": "./protractor.conf.js",
              "devServerTarget": "ng:serve"
            }
          },
          "lint": {
            "builder": "@angular-devkit/build-angular:tslint",
            "options": {
              "tsConfig": [
                "e2e/tsconfig.e2e.json"
              ],
              "exclude": [
                "**/node_modules/**"
              ]
            }
          }
        }
      }
    },
    "defaultProject": "ng",
    "schematics": {
      "@schematics/angular:component": {
        "prefix": "app",
        "styleext": "scss"
      },
      "@schematics/angular:directive": {
        "prefix": "app"
      }
    }
  }
  </code></pre>