When I try to use throwError from inside the catchError to return an error, I get the following deprecation message
The signature '(error: any): Observable' of 'throwError' is deprecated.(6387)
const { Observable, throwError } = rxjs;
const { catchError } = rxjs.operators;
new Observable((observer) => {
observer.next('first emission');
observer.error('error emission');
observer.complete();
}).pipe(
catchError((error) => {
console.log('Caught error:', error);
return throwError(error); // <-- deprecation here
})
).subscribe({
next: (value) => console.log('Next:', value),
error: (error) => console.log('Error:', error),
complete: () => console.log('Complete')
});.as-console-wrapper { max-height: 100% !important; top: 0px }<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.4.0/rxjs.umd.min.js"></script>Deprecation reproduction: Stackblitz
The reason for deprecation is explained here:
Support for passing an error value will be removed in v8. Instead, pass a factory function to
throwError(() => new Error('test')). This is
- because it will create the error at the moment it should be created and capture a more appropriate stack trace. If
- for some reason you need to create the error ahead of time, you can still do that:
const err = new Error('test'); throwError(() => err);
So we could either do
.pipe(
catchError((error) => {
return throwError(() => new Error(error));
})
).subscribe({
error: (error) => console.log('Error:', error.message)
});
or
.pipe(
catchError((error) => {
return throwError(() => error);
})
).subscribe({
error: (error) => console.log('Error:', error)
});
Working example: Stackblitz