import { Observable } from '../Observable';
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import { SchedulerLike } from '../types';
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import { Subscriber } from '../Subscriber';
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/**
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* Creates an Observable that emits no items to the Observer and immediately
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* emits an error notification.
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*
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* <span class="informal">Just emits 'error', and nothing else.
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* </span>
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*
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* 
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*
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* This static operator is useful for creating a simple Observable that only
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* emits the error notification. It can be used for composing with other
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* Observables, such as in a {@link mergeMap}.
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*
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* ## Examples
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* ### Emit the number 7, then emit an error
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* ```ts
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* import { throwError, concat, of } from 'rxjs';
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*
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* const result = concat(of(7), throwError(new Error('oops!')));
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* result.subscribe(x => console.log(x), e => console.error(e));
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*
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* // Logs:
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* // 7
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* // Error: oops!
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* ```
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*
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* ---
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*
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* ### Map and flatten numbers to the sequence 'a', 'b', 'c', but throw an error for 2
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* ```ts
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* import { throwError, interval, of } from 'rxjs';
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* import { mergeMap } from 'rxjs/operators';
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*
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* interval(1000).pipe(
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* mergeMap(x => x === 2
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* ? throwError('Twos are bad')
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* : of('a', 'b', 'c')
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* ),
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* ).subscribe(x => console.log(x), e => console.error(e));
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*
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* // Logs:
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* // a
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* // b
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* // c
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* // a
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* // b
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* // c
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* // Twos are bad
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* ```
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*
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* @see {@link Observable}
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* @see {@link empty}
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* @see {@link never}
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* @see {@link of}
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*
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* @param {any} error The particular Error to pass to the error notification.
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* @param {SchedulerLike} [scheduler] A {@link SchedulerLike} to use for scheduling
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* the emission of the error notification.
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* @return {Observable} An error Observable: emits only the error notification
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* using the given error argument.
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* @static true
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* @name throwError
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* @owner Observable
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*/
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export function throwError(error: any, scheduler?: SchedulerLike): Observable<never> {
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if (!scheduler) {
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return new Observable(subscriber => subscriber.error(error));
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} else {
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return new Observable(subscriber => scheduler.schedule(dispatch, 0, { error, subscriber }));
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}
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}
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interface DispatchArg {
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error: any;
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subscriber: Subscriber<any>;
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}
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function dispatch({ error, subscriber }: DispatchArg) {
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subscriber.error(error);
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}
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