Working fix for GET http://localhost:4200/null 404 (Not Found) in angular2 with angular-cli

Issue

I'm working with angular2 project with angular-cli. Today I updated version of below to 2.4.1.

"@angular/common": "~2.4.1",
"@angular/compiler": "~2.4.1",
"@angular/compiler-cli": "^2.4.1",
"@angular/core": "~2.4.1",
"@angular/forms": "~2.4.1",
"@angular/http": "~2.4.1",
"@angular/platform-browser": "~2.4.1",
"@angular/platform-browser-dynamic": "~2.4.1",
"@angular/router": "~3.4.1",
"angular-cli": "^1.0.0-beta.24"

When I used 2.0.0, it doesn't make an error, but now, it makes an error like GET http://localhost:4200/null 404 (Not Found).

Even though it makes an error, it's working well. However, I want to know why it happens, and fix this error. If anyone knows about this, please let me know. Thank you :)

Packages.json

{
  ...
  
  "private": true,
  "dependencies": {
    "@angular/common": "~2.4.1",
    "@angular/compiler": "~2.4.1",
    "@angular/compiler-cli": "^2.4.1",
    "@angular/core": "~2.4.1",
    "@angular/forms": "~2.4.1",
    "@angular/http": "~2.4.1",
    "@angular/material": "^2.0.0-beta.0",
    "@angular/platform-browser": "~2.4.1",
    "@angular/platform-browser-dynamic": "~2.4.1",
    "@angular/router": "~3.4.1",
    "@types/moment-timezone": "^0.2.33",
    "angular-cli": "^1.0.0-beta.24",
    "angular2-google-maps": "^0.17.0",
    "bootstrap": "^3.3.7",
    "bourbon": "^4.2.7",
    "core-js": "^2.4.1",
    "es6-promise": "^4.0.5",
    "font-awesome": "^4.7.0",
    "hammerjs": "^2.0.8",
    "moment": "^2.17.1",
    "moment-timezone": "^0.5.10",
    "node-sass": "^3.13.0",
    "primeng": "^1.1.0",
    "pubnub-angular2": "^1.0.0-beta.6",
    "quill": "^1.1.8",
    "rxjs": "5.0.1",
    "ts-helpers": "^1.1.1",
    "typescript": "^2.0.10",
    "typings": "^2.1.0",
    "zone.js": "^0.7.4"
  },
  "devDependencies": {
    "@types/hammerjs": "^2.0.33",
    "@types/jasmine": "^2.2.30",
    "@types/moment": "^2.13.0",
    "@types/moment-timezone": "^0.2.33",
    "@types/node": "^6.0.42",
    "angular-cli": "^1.0.0-beta.24",
    "bootstrap-sass": "^3.3.7",
    "codelyzer": "~0.0.26",
    "jasmine-core": "2.4.1",
    "jasmine-spec-reporter": "2.5.0",
    "karma": "1.2.0",
    "karma-chrome-launcher": "^2.0.0",
    "karma-cli": "^1.0.1",
    "karma-jasmine": "^1.0.2",
    "karma-remap-istanbul": "^0.2.1",
    "protractor": "4.0.9",
    "ts-loader": "^1.3.3",
    "ts-node": "1.2.1",
    "tslint": "4.2.0",
    "typescript": "2.0.2"
  }
}

angular-cli.json

{
  "project": {
    "version": "1.0.0-beta.24",
    "name": "five-delivery-admin"
  },
  "apps": [
    {
      "root": "src",
      "outDir": "dist",
      "assets": ["assets"],
      "index": "index.html",
      "main": "main.ts",
      "test": "test.ts",
      "tsconfig": "tsconfig.json",
      "prefix": "app",
      "mobile": false,
      "styles": [
        "styles.scss",
        "../node_modules/hammerjs/hammer.min.js",
        "../node_modules/primeng/resources/themes/omega/theme.css",
        "../node_modules/primeng/resources/primeng.min.css",
        "../node_modules/font-awesome/css/font-awesome.min.css",
        "../node_modules/bootstrap/dist/css/bootstrap.min.css",
        "../node_modules/quill/dist/quill.core.css",
        "../node_modules/quill/dist/quill.snow.css",
        "../node_modules/quill/dist/quill.bubble.css"
      ],
      "scripts": [
        "../node_modules/quill/dist/quill.min.js",
        "../node_modules/hammerjs/hammer.min.js"
      ],
      "environments": {
        "source": "environments/environment.ts",
        "dev": "environments/environment.ts",
        "prod": "environments/environment.prod.ts"
      }
    }
  ],
  "addons": [],
  "packages": [],
  "e2e": {
    "protractor": {
      "config": "./protractor.conf.js"
    }
  },
  "test": {
    "karma": {
      "config": "./karma.conf.js"
    }
  },
  "defaults": {
    "styleExt": "scss",
    "prefixInterfaces": false
  }
}

tsconfig.json

{
  "compilerOptions": {
    "declaration": false,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "lib": ["es6", "dom"],
    "mapRoot": "./",
    "module": "es6",
    "moduleResolution": "node",
    "outDir": "../dist/out-tsc",
    "sourceMap": true,
    "target": "es5",
    "typeRoots": [
      "../node_modules/@types"
    ]
  }
}

Solution

So I just had an exhausting time figuring this out, but I did.

This happened to me right after doing an update as well but it had nothing to do with that.

It's definitely from a reference to a variable with a null value and it's most likely an image src attribute. At least it was for me and I'm using values from a server all over the place in my app and img src were the only things causing this and it makes sense.

I had something similar to this:

<img [src]="myData?.imageUrl">

I thought that the ? safe operator would make sure I didn't get null errors, which it generally does but it seems like when you bind to a src attribute, the browser throws an error, not the compiler. The compiler lets you bind null to it because of the safe operator, but because src is a reference URL, the browser is still looking for that URL and the console throws the error because it can't find the URL relative/app/path/null

The two ways I found to solve this:

1. Use ngIf: <img *ngIf="myData" [src]="myData.imageUrl"/> (entire image and its src attribute never even get loaded if theres no data, avoiding the issue entirely)
2. Use interpolation: <img src="{{ myData?.imageUrl }}"/> (NOTICE in this solution you still need the safe operator because the compiler will throw an error otherwise, as expected, but now if the value is null, then src="" instead of null, which is valid HTML and wont throw a reference error)

Hope this helps!

Answered By - HauntedSmores