rxjs
Version:
Reactive Extensions for modern JavaScript
271 lines (247 loc) • 8.91 kB
text/typescript
import { isFunction } from './util/isFunction';
import { Observer, ObservableNotification } from './types';
import { isSubscription, Subscription } from './Subscription';
import { config } from './config';
import { reportUnhandledError } from './util/reportUnhandledError';
import { noop } from './util/noop';
import { nextNotification, errorNotification, COMPLETE_NOTIFICATION } from './NotificationFactories';
import { timeoutProvider } from './scheduler/timeoutProvider';
import { captureError } from './util/errorContext';
/**
* Implements the {@link Observer} interface and extends the
* {@link Subscription} class. While the {@link Observer} is the public API for
* consuming the values of an {@link Observable}, all Observers get converted to
* a Subscriber, in order to provide Subscription-like capabilities such as
* `unsubscribe`. Subscriber is a common type in RxJS, and crucial for
* implementing operators, but it is rarely used as a public API.
*/
export class Subscriber<T> extends Subscription implements Observer<T> {
/**
* A static factory for a Subscriber, given a (potentially partial) definition
* of an Observer.
* @param next The `next` callback of an Observer.
* @param error The `error` callback of an
* Observer.
* @param complete The `complete` callback of an
* Observer.
* @return A Subscriber wrapping the (partially defined)
* Observer represented by the given arguments.
* @deprecated Do not use. Will be removed in v8. There is no replacement for this
* method, and there is no reason to be creating instances of `Subscriber` directly.
* If you have a specific use case, please file an issue.
*/
static create<T>(next?: (x?: T) => void, error?: (e?: any) => void, complete?: () => void): Subscriber<T> {
return new SafeSubscriber(next, error, complete);
}
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
protected isStopped: boolean = false;
/** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
protected destination: Subscriber<any> | Observer<any>; // this `any` is the escape hatch to erase extra type param (e.g. R)
/**
* @deprecated Internal implementation detail, do not use directly. Will be made internal in v8.
* There is no reason to directly create an instance of Subscriber. This type is exported for typings reasons.
*/
constructor(destination?: Subscriber<any> | Observer<any>) {
super();
if (destination) {
this.destination = destination;
// Automatically chain subscriptions together here.
// if destination is a Subscription, then it is a Subscriber.
if (isSubscription(destination)) {
destination.add(this);
}
} else {
this.destination = EMPTY_OBSERVER;
}
}
/**
* The {@link Observer} callback to receive notifications of type `next` from
* the Observable, with a value. The Observable may call this method 0 or more
* times.
* @param value The `next` value.
*/
next(value: T): void {
if (this.isStopped) {
handleStoppedNotification(nextNotification(value), this);
} else {
this._next(value!);
}
}
/**
* The {@link Observer} callback to receive notifications of type `error` from
* the Observable, with an attached `Error`. Notifies the Observer that
* the Observable has experienced an error condition.
* @param err The `error` exception.
*/
error(err?: any): void {
if (this.isStopped) {
handleStoppedNotification(errorNotification(err), this);
} else {
this.isStopped = true;
this._error(err);
}
}
/**
* The {@link Observer} callback to receive a valueless notification of type
* `complete` from the Observable. Notifies the Observer that the Observable
* has finished sending push-based notifications.
*/
complete(): void {
if (this.isStopped) {
handleStoppedNotification(COMPLETE_NOTIFICATION, this);
} else {
this.isStopped = true;
this._complete();
}
}
unsubscribe(): void {
if (!this.closed) {
this.isStopped = true;
super.unsubscribe();
this.destination = null!;
}
}
protected _next(value: T): void {
this.destination.next(value);
}
protected _error(err: any): void {
try {
this.destination.error(err);
} finally {
this.unsubscribe();
}
}
protected _complete(): void {
try {
this.destination.complete();
} finally {
this.unsubscribe();
}
}
}
/**
* This bind is captured here because we want to be able to have
* compatibility with monoid libraries that tend to use a method named
* `bind`. In particular, a library called Monio requires this.
*/
const _bind = Function.prototype.bind;
function bind<Fn extends (...args: any[]) => any>(fn: Fn, thisArg: any): Fn {
return _bind.call(fn, thisArg);
}
/**
* Internal optimization only, DO NOT EXPOSE.
* @internal
*/
class ConsumerObserver<T> implements Observer<T> {
constructor(private partialObserver: Partial<Observer<T>>) {}
next(value: T): void {
const { partialObserver } = this;
if (partialObserver.next) {
try {
partialObserver.next(value);
} catch (error) {
handleUnhandledError(error);
}
}
}
error(err: any): void {
const { partialObserver } = this;
if (partialObserver.error) {
try {
partialObserver.error(err);
} catch (error) {
handleUnhandledError(error);
}
} else {
handleUnhandledError(err);
}
}
complete(): void {
const { partialObserver } = this;
if (partialObserver.complete) {
try {
partialObserver.complete();
} catch (error) {
handleUnhandledError(error);
}
}
}
}
export class SafeSubscriber<T> extends Subscriber<T> {
constructor(
observerOrNext?: Partial<Observer<T>> | ((value: T) => void) | null,
error?: ((e?: any) => void) | null,
complete?: (() => void) | null
) {
super();
let partialObserver: Partial<Observer<T>>;
if (isFunction(observerOrNext) || !observerOrNext) {
// The first argument is a function, not an observer. The next
// two arguments *could* be observers, or they could be empty.
partialObserver = {
next: (observerOrNext ?? undefined) as ((value: T) => void) | undefined,
error: error ?? undefined,
complete: complete ?? undefined,
};
} else {
// The first argument is a partial observer.
let context: any;
if (this && config.useDeprecatedNextContext) {
// This is a deprecated path that made `this.unsubscribe()` available in
// next handler functions passed to subscribe. This only exists behind a flag
// now, as it is *very* slow.
context = Object.create(observerOrNext);
context.unsubscribe = () => this.unsubscribe();
partialObserver = {
next: observerOrNext.next && bind(observerOrNext.next, context),
error: observerOrNext.error && bind(observerOrNext.error, context),
complete: observerOrNext.complete && bind(observerOrNext.complete, context),
};
} else {
// The "normal" path. Just use the partial observer directly.
partialObserver = observerOrNext;
}
}
// Wrap the partial observer to ensure it's a full observer, and
// make sure proper error handling is accounted for.
this.destination = new ConsumerObserver(partialObserver);
}
}
function handleUnhandledError(error: any) {
if (config.useDeprecatedSynchronousErrorHandling) {
captureError(error);
} else {
// Ideal path, we report this as an unhandled error,
// which is thrown on a new call stack.
reportUnhandledError(error);
}
}
/**
* An error handler used when no error handler was supplied
* to the SafeSubscriber -- meaning no error handler was supplied
* do the `subscribe` call on our observable.
* @param err The error to handle
*/
function defaultErrorHandler(err: any) {
throw err;
}
/**
* A handler for notifications that cannot be sent to a stopped subscriber.
* @param notification The notification being sent.
* @param subscriber The stopped subscriber.
*/
function handleStoppedNotification(notification: ObservableNotification<any>, subscriber: Subscriber<any>) {
const { onStoppedNotification } = config;
onStoppedNotification && timeoutProvider.setTimeout(() => onStoppedNotification(notification, subscriber));
}
/**
* The observer used as a stub for subscriptions where the user did not
* pass any arguments to `subscribe`. Comes with the default error handling
* behavior.
*/
export const EMPTY_OBSERVER: Readonly<Observer<any>> & { closed: true } = {
closed: true,
next: noop,
error: defaultErrorHandler,
complete: noop,
};