import { PartialObserver, ObservableNotification, CompleteNotification, NextNotification, ErrorNotification } from './types';
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import { Observable } from './Observable';
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import { EMPTY } from './observable/empty';
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import { of } from './observable/of';
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import { throwError } from './observable/throwError';
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import { isFunction } from './util/isFunction';
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// TODO: When this enum is removed, replace it with a type alias. See #4556.
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/**
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* @deprecated Use a string literal instead. `NotificationKind` will be replaced with a type alias in v8.
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* It will not be replaced with a const enum as those are not compatible with isolated modules.
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*/
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export enum NotificationKind {
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NEXT = 'N',
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ERROR = 'E',
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COMPLETE = 'C',
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}
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/**
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* Represents a push-based event or value that an {@link Observable} can emit.
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* This class is particularly useful for operators that manage notifications,
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* like {@link materialize}, {@link dematerialize}, {@link observeOn}, and
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* others. Besides wrapping the actual delivered value, it also annotates it
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* with metadata of, for instance, what type of push message it is (`next`,
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* `error`, or `complete`).
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*
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* @see {@link materialize}
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* @see {@link dematerialize}
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* @see {@link observeOn}
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* @deprecated It is NOT recommended to create instances of `Notification` directly.
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* Rather, try to create POJOs matching the signature outlined in {@link ObservableNotification}.
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* For example: `{ kind: 'N', value: 1 }`, `{ kind: 'E', error: new Error('bad') }`, or `{ kind: 'C' }`.
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* Will be removed in v8.
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*/
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export class Notification<T> {
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/**
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* A value signifying that the notification will "next" if observed. In truth,
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* This is really synonymous with just checking `kind === "N"`.
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* @deprecated Will be removed in v8. Instead, just check to see if the value of `kind` is `"N"`.
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*/
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readonly hasValue: boolean;
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/**
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* Creates a "Next" notification object.
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* @param kind Always `'N'`
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* @param value The value to notify with if observed.
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* @deprecated Internal implementation detail. Use {@link Notification#createNext createNext} instead.
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*/
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constructor(kind: 'N', value?: T);
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/**
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* Creates an "Error" notification object.
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* @param kind Always `'E'`
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* @param value Always `undefined`
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* @param error The error to notify with if observed.
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* @deprecated Internal implementation detail. Use {@link Notification#createError createError} instead.
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*/
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constructor(kind: 'E', value: undefined, error: any);
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/**
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* Creates a "completion" notification object.
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* @param kind Always `'C'`
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* @deprecated Internal implementation detail. Use {@link Notification#createComplete createComplete} instead.
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*/
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constructor(kind: 'C');
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constructor(public readonly kind: 'N' | 'E' | 'C', public readonly value?: T, public readonly error?: any) {
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this.hasValue = kind === 'N';
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}
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/**
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* Executes the appropriate handler on a passed `observer` given the `kind` of notification.
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* If the handler is missing it will do nothing. Even if the notification is an error, if
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* there is no error handler on the observer, an error will not be thrown, it will noop.
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* @param observer The observer to notify.
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*/
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observe(observer: PartialObserver<T>): void {
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return observeNotification(this as ObservableNotification<T>, observer);
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}
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/**
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* Executes a notification on the appropriate handler from a list provided.
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* If a handler is missing for the kind of notification, nothing is called
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* and no error is thrown, it will be a noop.
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* @param next A next handler
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* @param error An error handler
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* @param complete A complete handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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do(next: (value: T) => void, error: (err: any) => void, complete: () => void): void;
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/**
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* Executes a notification on the appropriate handler from a list provided.
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* If a handler is missing for the kind of notification, nothing is called
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* and no error is thrown, it will be a noop.
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* @param next A next handler
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* @param error An error handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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do(next: (value: T) => void, error: (err: any) => void): void;
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/**
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* Executes the next handler if the Notification is of `kind` `"N"`. Otherwise
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* this will not error, and it will be a noop.
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* @param next The next handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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do(next: (value: T) => void): void;
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do(nextHandler: (value: T) => void, errorHandler?: (err: any) => void, completeHandler?: () => void): void {
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const { kind, value, error } = this;
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return kind === 'N' ? nextHandler?.(value!) : kind === 'E' ? errorHandler?.(error) : completeHandler?.();
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}
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/**
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* Executes a notification on the appropriate handler from a list provided.
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* If a handler is missing for the kind of notification, nothing is called
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* and no error is thrown, it will be a noop.
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* @param next A next handler
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* @param error An error handler
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* @param complete A complete handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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accept(next: (value: T) => void, error: (err: any) => void, complete: () => void): void;
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/**
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* Executes a notification on the appropriate handler from a list provided.
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* If a handler is missing for the kind of notification, nothing is called
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* and no error is thrown, it will be a noop.
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* @param next A next handler
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* @param error An error handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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accept(next: (value: T) => void, error: (err: any) => void): void;
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/**
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* Executes the next handler if the Notification is of `kind` `"N"`. Otherwise
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* this will not error, and it will be a noop.
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* @param next The next handler
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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accept(next: (value: T) => void): void;
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/**
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* Executes the appropriate handler on a passed `observer` given the `kind` of notification.
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* If the handler is missing it will do nothing. Even if the notification is an error, if
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* there is no error handler on the observer, an error will not be thrown, it will noop.
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* @param observer The observer to notify.
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* @deprecated Replaced with {@link Notification#observe observe}. Will be removed in v8.
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*/
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accept(observer: PartialObserver<T>): void;
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accept(nextOrObserver: PartialObserver<T> | ((value: T) => void), error?: (err: any) => void, complete?: () => void) {
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return isFunction((nextOrObserver as any)?.next)
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? this.observe(nextOrObserver as PartialObserver<T>)
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: this.do(nextOrObserver as (value: T) => void, error as any, complete as any);
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}
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/**
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* Returns a simple Observable that just delivers the notification represented
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* by this Notification instance.
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*
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* @deprecated Will be removed in v8. To convert a `Notification` to an {@link Observable},
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* use {@link of} and {@link dematerialize}: `of(notification).pipe(dematerialize())`.
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*/
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toObservable(): Observable<T> {
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const { kind, value, error } = this;
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// Select the observable to return by `kind`
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const result =
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kind === 'N'
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? // Next kind. Return an observable of that value.
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of(value!)
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: //
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kind === 'E'
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? // Error kind. Return an observable that emits the error.
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throwError(() => error)
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: //
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kind === 'C'
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? // Completion kind. Kind is "C", return an observable that just completes.
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EMPTY
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: // Unknown kind, return falsy, so we error below.
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0;
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if (!result) {
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// TODO: consider removing this check. The only way to cause this would be to
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// use the Notification constructor directly in a way that is not type-safe.
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// and direct use of the Notification constructor is deprecated.
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throw new TypeError(`Unexpected notification kind ${kind}`);
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}
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return result;
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}
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private static completeNotification = new Notification('C') as Notification<never> & CompleteNotification;
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/**
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* A shortcut to create a Notification instance of the type `next` from a
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* given value.
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* @param {T} value The `next` value.
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* @return {Notification<T>} The "next" Notification representing the
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* argument.
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* @nocollapse
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* @deprecated It is NOT recommended to create instances of `Notification` directly.
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* Rather, try to create POJOs matching the signature outlined in {@link ObservableNotification}.
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* For example: `{ kind: 'N', value: 1 }`, `{ kind: 'E', error: new Error('bad') }`, or `{ kind: 'C' }`.
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* Will be removed in v8.
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*/
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static createNext<T>(value: T) {
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return new Notification('N', value) as Notification<T> & NextNotification<T>;
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}
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/**
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* A shortcut to create a Notification instance of the type `error` from a
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* given error.
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* @param {any} [err] The `error` error.
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* @return {Notification<T>} The "error" Notification representing the
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* argument.
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* @nocollapse
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* @deprecated It is NOT recommended to create instances of `Notification` directly.
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* Rather, try to create POJOs matching the signature outlined in {@link ObservableNotification}.
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* For example: `{ kind: 'N', value: 1 }`, `{ kind: 'E', error: new Error('bad') }`, or `{ kind: 'C' }`.
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* Will be removed in v8.
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*/
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static createError(err?: any) {
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return new Notification('E', undefined, err) as Notification<never> & ErrorNotification;
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}
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/**
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* A shortcut to create a Notification instance of the type `complete`.
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* @return {Notification<any>} The valueless "complete" Notification.
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* @nocollapse
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* @deprecated It is NOT recommended to create instances of `Notification` directly.
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* Rather, try to create POJOs matching the signature outlined in {@link ObservableNotification}.
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* For example: `{ kind: 'N', value: 1 }`, `{ kind: 'E', error: new Error('bad') }`, or `{ kind: 'C' }`.
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* Will be removed in v8.
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*/
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static createComplete(): Notification<never> & CompleteNotification {
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return Notification.completeNotification;
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}
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}
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/**
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* Executes the appropriate handler on a passed `observer` given the `kind` of notification.
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* If the handler is missing it will do nothing. Even if the notification is an error, if
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* there is no error handler on the observer, an error will not be thrown, it will noop.
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* @param notification The notification object to observe.
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* @param observer The observer to notify.
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*/
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export function observeNotification<T>(notification: ObservableNotification<T>, observer: PartialObserver<T>) {
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const { kind, value, error } = notification as any;
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if (typeof kind !== 'string') {
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throw new TypeError('Invalid notification, missing "kind"');
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}
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kind === 'N' ? observer.next?.(value!) : kind === 'E' ? observer.error?.(error) : observer.complete?.();
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}
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