CODEWITHSUNDEEP
rxjs
jmls
jmls

Reputation: 2969

handle http errors in rxjs lastValueFrom

I have started to use the lastValueFrom() to handle my observable http requests. One of these http calls is returning an error from the server-side, and I am getting the name: 'EmptyError', message: 'no elements in sequence' message

const response = await lastValueFrom(
        this.service.doStuff()
    ).catch((e) => {
        console.log('#1', e);
        return {} as DoStuffResponse;
    });

at #1 the error is EmptyError , not the error from the http call.

I understand why I am getting it (the http observable does not return a value)

However, what I'd like to know is what the actual error is (a 422 unprocessable entity in this case)

Is this possible ?

Upvotes: 4

Views: 8637

Answers (3)

Jose A
Jose A

Reputation: 11077

I was having the same issue with NestJS. The solution was to wrap it in a try/catch clause:

 async myFunctionOrMethod(
    myPayload: any
  ): Promise<Result<Response, Err>> {

    try {
      const result = await lastValueFrom(
        this.httpService.post('/api/endpoint', { myPayload})
      );
      return Ok(result.data as Response);
    } catch (err) {
      return Err(new InternalServerErrorException(err));
    }

  }

Upvotes: 1

Yassir Khaldi
Yassir Khaldi

Reputation: 1752

You do actually have the possibility to gracefully catch errors from lastValueFrom like this:

firstValueFrom(this.http.post(url, body))
.catch((error: HttpErrorResponse) => {
  console.log("error: ", error);
  return "an error has occured"
}).then(response => {
  // In case of an error this will receive "an error has occured" as a response
  console.log("resp: ", response)
});

Upvotes: 3

shage_in_excelsior
shage_in_excelsior

Reputation: 193

I have not found a method to catch the Http errors from lastValueFrom and this does not appear to be documented in rxjs.

As a result I've decided to avoid lastValueFrom when doing Http requests. Instead I stick with Subscribe and always get the Http response codes in the error.

As an aside, many people noticed Subscribe as being deprecated in VSCode, but this is not true; just a certain overload. I know you didn't mention the deprecation as a motivator for using lastValueFrom, but I think most people, including myself, used the VSCode deprecation alert as a prompt to switch.

That said, this Subscribe syntax is still valid and should give you the Http error code:

this.someService.getResults.subscribe(
{
  next: (results) => {
    console.log('Here are the results...', results);
  },

  error: (err: any) => { 
    console.log('Here is the error...', err.status);
  },
  complete: () => { }

});

Upvotes: 2

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