ng serve with --aot or --prod flag, doesn't build with ES2015 support

[hugodes]

🐞 Bug report

Command (mark with an x)

- [ ] new
- [ ] build
- [x] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Is this a regression?

Not to my knowledge.

Description

When running the command:

ng serve --aot
or
ng serve --prod

The served html doesn't output with es2015 / differential loading.

🔬 Minimal Reproduction

I created a bear-bones ng8 project that shows the issue.
https://github.com/hugodes/cli-2015

script includes part of the html are:

<script src="runtime.858f8dd898b75fe86926.js"></script><script src="polyfills-es5.f50c7749278f35217fe9.js" nomodule></script><script src="polyfills.c87fd890b4d24e91db1e.js"></script><script src="main.c83376d1497eb7bd76af.js"></script></body>

should be:

<script src="runtime-es2015.858f8dd898b75fe86926.js" type="module"></script><script src="polyfills-es2015.559e7c8b3a629fdb5581.js" type="module"></script><script src="runtime-es5.741402d1d47331ce975c.js" nomodule></script><script src="polyfills-es5.2e5f0eafe40ded881b53.js" nomodule></script><script src="main-es2015.98e01c2f839116c6f30d.js" type="module"></script><script src="main-es5.3a0b969a3eb452415775.js" nomodule></script></body>

🌍 Your Environment

```
Angular CLI: 8.0.2
Node: 10.16.0
OS: darwin x64
Angular: 8.0.0
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.800.2
@angular-devkit/build-angular     0.800.2
@angular-devkit/build-optimizer   0.800.2
@angular-devkit/build-webpack     0.800.2
@angular-devkit/core              8.0.2
@angular-devkit/schematics        8.0.2
@angular/cli                      8.0.2
@ngtools/webpack                  8.0.2
@schematics/angular               8.0.2
@schematics/update                0.800.2
rxjs                              6.5.2
typescript                        3.4.5
webpack                           4.30.0
```

Anything else relevant?

tsconfig.json:

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "importHelpers": true,
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "module": "esnext",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es2015",
    "typeRoots": [
      "node_modules/@types"
    ],
    "lib": [
      "es2018",
      "dom"
    ]
  }
}

angular.json:

{
  "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
  "version": 1,
  "newProjectRoot": "projects",
  "projects": {
    "error": {
      "root": "",
      "sourceRoot": "src",
      "projectType": "application",
      "prefix": "app",
      "schematics": {},
      "architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "outputPath": "dist/error",
            "index": "src/index.html",
            "main": "src/main.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.app.json",
            "assets": [
              "src/favicon.ico",
              "src/assets"
            ],
            "styles": [
              "src/styles.css"
            ],
            "scripts": []
          },
          "configurations": {
            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "optimization": true,
              "outputHashing": "all",
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "budgets": [
                {
                  "type": "initial",
                  "maximumWarning": "2mb",
                  "maximumError": "5mb"
                }
              ]
            }
          }
        },
        "serve": {
          "builder": "@angular-devkit/build-angular:dev-server",
          "options": {
            "browserTarget": "error:build"
          },
          "configurations": {
            "production": {
              "browserTarget": "error:build:production"
            }
          }
        },
        "extract-i18n": {
          "builder": "@angular-devkit/build-angular:extract-i18n",
          "options": {
            "browserTarget": "error:build"
          }
        },
        "test": {
          "builder": "@angular-devkit/build-angular:karma",
          "options": {
            "main": "src/test.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.spec.json",
            "karmaConfig": "src/karma.conf.js",
            "styles": [
              "src/styles.css"
            ],
            "scripts": [],
            "assets": [
              "src/favicon.ico",
              "src/assets"
            ]
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": [
              "src/tsconfig.app.json",
              "src/tsconfig.spec.json"
            ],
            "exclude": [
              "**/node_modules/**"
            ]
          }
        }
      }
    },
    "error-e2e": {
      "root": "e2e/",
      "projectType": "application",
      "prefix": "",
      "architect": {
        "e2e": {
          "builder": "@angular-devkit/build-angular:protractor",
          "options": {
            "protractorConfig": "e2e/protractor.conf.js",
            "devServerTarget": "error:serve"
          },
          "configurations": {
            "production": {
              "devServerTarget": "error:serve:production"
            }
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": "e2e/tsconfig.e2e.json",
            "exclude": [
              "**/node_modules/**"
            ]
          }
        }
      }
    }
  },
  "defaultProject": "error"
}

[alan-agius4]

Hi, thanks for opening this but differential loading is only enabled on ng build. The main reason behind this is that differential loading requires 2 builds which during development it will hinder the development experience.

That said, during serve and test, we will only generate the ES2015 bundle as this is now the default script target configuration in the tsconfig.json.

[hugodes]

Thanks @alan-agius4 , I created a new issue with the underlying problem I was having here : #14747

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