Error in Angular 4: Unexpected 'undefined' provided instead of a stream

Question

Error in Angular 4: Unexpected 'undefined' provided instead of a stream

I encountered an issue while attempting to make a HTTP Post request. The error message I received is as follows:

auth.service.ts?c694:156 Something went wrong requesting a new password, error message: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

The first Http request preceding this one works perfectly fine.

This is the code snippet of my component calling the service:

requestNewPassword(formInput: NgForm) {
     if(formInput.controls['email'].value != '')
      this.authService.getApplicationAccessToken()
      .mergeMap((response: IAuthAppResponse) => this.authService.requestNewPassword(formInput, response.access_token))
      .subscribe(response => {
        // Content removed for simplicity
      })
    }

Below is the service method generating the aforementioned error:

public requestNewPassword(formData: NgForm, applicationAccessToken: string): Observable<any> {
      let headers = new HttpHeaders({
        'Authorization':'Bearer ' + applicationAccessToken
      });
      let email: string = formData.controls['email'].value;
      const body = {
        email: email
      };

      console.log('requestNewPassword call header: ' + headers.get('Authorization'));
      console.log('Email: ' + body.email);

      return this.http.post(this.baseUrl + '/api/user/password/forgot', body, {headers}).do(response => {
        console.log("New password was successfully sent to the e-mail adress");
      }).catch((error: HttpErrorResponse) => {
        console.log('Something went wrong requesting a new password, error message: ' + error.message);
        return Observable.throw(error);
      })
    }

Whenever I submit an email through the form, triggering the requestNewPassword method in the component, I encounter the previously mentioned error from the service.

The logged header and email values are correct, so it seems that the data being provided is not the issue.

As I am unsure how to debug this further, I decided to seek assistance by posting this question here.

Thank you in advance!

Update

In an effort to pinpoint the problem, I have streamlined the code in my component by eliminating the chaining of the two HTTP requests and only executing the second one which is causing trouble.

requestNewPassword(formInput: NgForm) {
      if(formInput.controls['email'].value != '')
      this.authService.requestNewPassword(formInput, "")
       .subscribe(response => {
         // Content removed for simplicity
       })
     }

A complete stack trace is now displayed:

ERROR TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable...
    at Object.subscribeToResult (subscribeToResult.js?c011:74)
    ...
    at HTMLFormElement.globalZoneAwareCallback (zone.js?fad3:1566)

Since there is mention of html in the error message, I will also include the corresponding html code:

<form class="custom_form" #requestNewPasswordForm="ngForm" (ngSubmit)="requestNewPassword(requestNewPasswordForm)">
    <label>E-mail</label>
    <input class="custom_input" type="email" class="inputfield form-control" ngModel name="email">
    <button class="btn btn-default" type="submit">
      Send
    </button>
</form>

angular http typescript rxjs

Answer 1

Answer №1

Through persistent effort, I successfully identified and resolved the issue at hand. The root of the problem lay with an authorization interceptor that was intercepting all requests to insert an Authorization header with a user access token.

The specific call I was making did not necessitate a user access token, but rather an application access token (for authenticating as an application for public HTTP requests such as registration and password resets). To solve this, I decided to chain together the calls to retrieve the application access token and request the forgotten password. Subsequently, I passed the obtained application access token to the forgot password method in my service and set it in the Authorization header there. The code for this process functioned correctly. However, the issue arose from my modification of the interceptor to check for the presence of an Authorization header. If present, the interceptor would do nothing – this oversight led to the bug.

Instead of taking no action, I should have simply returned the request so it could proceed without alterations to the header.

Therefore, rather than:

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if(request.headers.get('Authorization') == null) {
          //Code to add Authorization header
          return next.handle(requestWithAuthHeader)
        }
}

I had to implement the following:

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if(request.headers.get('Authorization') == null) {
          //Code to add Authorization header
          return next.handle(requestWithAuthHeader)
        } else {
          return next.handle(request);
        }
}

Otherwise, the request would be intercepted and never executed since it wasn't being returned by the interceptor. The method in my component was subscribed to the service method's result, expecting an observable. However, nothing was returned due to the interception of the request and the inaction of the interceptor upon detecting an existing Authorization header (already set within the service).

This clarifies why I encountered the error stating that undefined was provided when an observable stream was expected on the subscribe line within my component's method.

Answer 2

Through persistent effort, I successfully identified and resolved the issue at hand. The root of the problem lay with an authorization interceptor that was intercepting all requests to insert an Authorization header with a user access token.

The specific call I was making did not necessitate a user access token, but rather an application access token (for authenticating as an application for public HTTP requests such as registration and password resets). To solve this, I decided to chain together the calls to retrieve the application access token and request the forgotten password. Subsequently, I passed the obtained application access token to the forgot password method in my service and set it in the Authorization header there. The code for this process functioned correctly. However, the issue arose from my modification of the interceptor to check for the presence of an Authorization header. If present, the interceptor would do nothing – this oversight led to the bug.

Instead of taking no action, I should have simply returned the request so it could proceed without alterations to the header.

Therefore, rather than:

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if(request.headers.get('Authorization') == null) {
          //Code to add Authorization header
          return next.handle(requestWithAuthHeader)
        }
}

I had to implement the following:

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if(request.headers.get('Authorization') == null) {
          //Code to add Authorization header
          return next.handle(requestWithAuthHeader)
        } else {
          return next.handle(request);
        }
}

Otherwise, the request would be intercepted and never executed since it wasn't being returned by the interceptor. The method in my component was subscribed to the service method's result, expecting an observable. However, nothing was returned due to the interception of the request and the inaction of the interceptor upon detecting an existing Authorization header (already set within the service).

This clarifies why I encountered the error stating that undefined was provided when an observable stream was expected on the subscribe line within my component's method.

Answer 3

Answer №2

Dealing with a similar issue, I discovered the root of the problem lay in an HTTP interceptor. My predicament stemmed from having an automatic deserialization function set up for all responses following a specific API endpoint pattern. This setup caused any responses that were not instances of HTTPResponse to vanish into thin air. To remedy this, I included an else statement that simply returned the response untouched if it did not match the HTTPResponse instance:

@Injectable()
export class DeserializerInterceptor implements HttpInterceptor {
  public intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request).map(
      event => {
        if (event instanceof HttpResponse) {
          let response = event as HttpResponse<any>;
          // ... code for deserializing response object
          return response;
        } else {
          return event; // ... introducing this else statement resolved the `undefined` error.
        }
      }
    );
  }
}

(Omitted error handling details for better understanding.)

Answer 4

Dealing with a similar issue, I discovered the root of the problem lay in an HTTP interceptor. My predicament stemmed from having an automatic deserialization function set up for all responses following a specific API endpoint pattern. This setup caused any responses that were not instances of HTTPResponse to vanish into thin air. To remedy this, I included an else statement that simply returned the response untouched if it did not match the HTTPResponse instance:

@Injectable()
export class DeserializerInterceptor implements HttpInterceptor {
  public intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request).map(
      event => {
        if (event instanceof HttpResponse) {
          let response = event as HttpResponse<any>;
          // ... code for deserializing response object
          return response;
        } else {
          return event; // ... introducing this else statement resolved the `undefined` error.
        }
      }
    );
  }
}

(Omitted error handling details for better understanding.)

Error in Angular 4: Unexpected 'undefined' provided instead of a stream

Answer №1

Answer №2

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