http.get (urlFromFirebase) .text () пуст. Он дает 'syntaxerror-unknown-end-of- json -input' после JSON .Parse

Question

Когда я вызываю http из firebase в Angular9, кажется, что ответ нулевой, потому что .text () в ответ дает null. 'https://firestore.googleapis.com/v1/projects/angularfirebasegb/databases/ (по умолчанию) / documents / cart? Key = AIzaSyDNW48hAmvH8eAZpbeflRKb0khY5Blzsqg Это URL-адрес запроса, я разрешаю любому пользователю читать / отправлять текст. На самом деле у меня есть эта проблема с использованием теста Кармы в классе:

- cart.service.spe c .ts--

import { TestBed, inject, fakeAsync, tick } from '@angular/core/testing';
import { CartService } from './cart.service';
import { AngularFireModule } from '@angular/fire';
import { AngularFirestore, AngularFirestoreModule } from '@angular/fire/firestore';
import { CartList } from './cart.services.mock';
import { Observable } from 'rxjs';
import { MockBackend } from '@angular/http/testing';
import { Http, ConnectionBackend, BaseRequestOptions, Response } from '@angular/http';
import { httpFactory } from '@angular/http/src/http_module';
import { JsonPipe } from '@angular/common';

export const environment = {
  production: false,
  firebase: {
    apiKey: "AIzaSyDNW48hAmvH8eAZpbeflRKb0khY5Blzsqg",
    authDomain: "angularfirebasegb.firebaseapp.com",
    databaseURL: "https://angularfirebasegb.firebaseio.com",
    projectId: "angularfirebasegb",
    storageBucket: "angularfirebasegb.appspot.com",
    messagingSenderId: "388340512107",
    appId: "1:388340512107:web:2cf5e9a1daea5cfaf1082e",
    measurementId: "G-L43R4QN2LN"
  }
};

let AngularFireStoreMock = {
  collection: function (param: any) {
    return {
      // mime valueChanges in cart.service.ts
      valueChanges: function () { return Observable.of(CartList) },
      add: function (item) { return item }
    }
  }
}

describe('CartService', () => {
  let service: CartService;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        AngularFireModule.initializeApp(environment.firebase),
        AngularFirestoreModule
      ],
      providers: [
        CartService,
        { provide: AngularFirestore, useValue: AngularFireStoreMock },
        BaseRequestOptions,
        MockBackend,
        {
          provide: Http,
          useFactory: (backend: ConnectionBackend, defaultOptions: BaseRequestOptions) => {
            return new Http(backend, defaultOptions);
          },
          // dependencies
          deps: [MockBackend, BaseRequestOptions]
        }
      ]
    });
    service = TestBed.inject(CartService);
  });

  it('should have callHttp woeking', inject([CartService, MockBackend], fakeAsync((service: CartService, backend: MockBackend) => {
    let responseFromBackEnd;

    let response =
    {
      "documents": [
        {
          "name": "projects/angularfirebasegb/databases/(default)/documents/cart/dhnV5jYUPDTOUZyfGDw1",
          "fields": {
            "genre": {
              "mapValue": {}
            },
            "category": {
              "stringValue": ""
            },
            "price": {
              "doubleValue": 100.1
            },
            "title": {
              "stringValue": "Hello world"
            },
            "description": {
              "stringValue": "Hello world description"
            }, 
            "image": {
              "stringValue": "https://image.shutterstock.com/image-photo/white-transparent-leaf-on-mirror-260nw-1029171697.jpg"
            },
            "upvotes": {
              "integerValue": "0"
            }
          },
          "createTime": "2020-05-03T23:03:37.329754Z",
          "updateTime": "2020-05-03T23:09:04.281872Z"
        }
      ]
    };

    backend.connections.subscribe(connection => {
      connection.mockRespond(new Response(<any>{
        body: JSON.stringify(Response)
      }));
    });

    service.httpCall().subscribe(data => {
      responseFromBackEnd = data;
    });

    tick();
    let jsonFromBackend = JSON.parse(responseFromBackEnd.text());

    expect(jsonFromBackend).toEqual(response);
  }))
  );

  it('should be created', inject([CartService], (service: CartService) => {
    expect(service).toBeTruthy();
  }));

  it('should have add method defined', inject([CartService], (service: CartService) => {
    expect(service.add).toBeTruthy();
  }));

  it('should have query method defined', inject([CartService], (service: CartService) => {
    expect(service.query).toBeTruthy();
  }));

  it('should have query method defined working', inject([CartService], fakeAsync((service: CartService) => {
    let all$ = service.query();
    let response;

    // NOMINARE LE VARIABILI DI TIPO OBSERVABLE CON IL '$', PER CONVENZIONE. TUTTAVIA NON E' OBBLIGATORIO
    all$.subscribe((items) => {
      response = items;
    });

    // use tick because is an asyncronous call, thus go ahed and do all the necesary changes
    tick();

    expect(response).toBe(CartList);
  })));
});

У меня есть исключение в этой строке:

let jsonFromBackend = JSON.parse(responseFromBackEnd.text());

, и исключение следующее:

SyntaxError: Unexpected end of JSON input

Это потому, что responseFromBackend содержит:

headers: undefined
ok: false
status: undefined
statusText: undefined
type: undefined
url: undefined
_body: undefined
__proto__: Body

и пытается выполнить синтаксический анализ json пустой строки (на самом деле значение responseFromBackEnd.text () равно «»).

httpCall ( ) метод определяется в:

- cart.service.ts -

import { Injectable } from '@angular/core';
// install rxjs first: npm install rxjs-compat --save
import { Observable } from 'rxjs/Observable';
import { BookModel } from '../../models/book/book.model';
import { Subject } from 'rxjs/Subject';
import { AngularFirestore } from '@angular/fire/firestore';
//import { AngularFirestore } from 'angularfire2/firestore';
// se non presente: npm install @angular/http@latest
import { Http } from '@angular/http';


@Injectable({
  providedIn: 'root'
})
export class CartService {
  private emitAddToCart = new Subject<any>();
  addEmitted$ = this.emitAddToCart.asObservable();
  // http requests (https://firebase.google.com/docs/firestore/use-rest-api) example of httprequest
  hardCodeUrl = 'https://firestore.googleapis.com/v1/projects/angularfirebasegb/databases/(default)/documents/cart?key=AIzaSyDNW48hAmvH8eAZpbeflRKb0khY5Blzsqg';


  constructor(private db: AngularFirestore, private http: Http) { }

    query() {
      // promise
      return this.db.collection('/cart').valueChanges();
    }

  add(data){
    // this is going to put some items into an item collection, storing data in firebase
    let item = this.db.collection<BookModel>('/cart').add(data.getData());
    // next is going to do all the save for us (but the name is a quite strange)
    this.emitAddToCart.next(item);
    return item;
  }

  emitChange(book: BookModel) {
    this.emitAddToCart.next(book);
  }

  httpCall() {
    debugger;
    return this.http.get(this.hardCodeUrl);
  }
}

Не знаю, чтобы разобраться, я новичок в angular