fix(subscriber): unsubscribe parents on error/complete

src/internal/Observable.ts

@@ -198,7 +198,7 @@ export class Observable<T> implements Subscribable<T> {
     if (operator) {
       operator.call(sink, this.source);
     } else {
-      sink.add(
+      sink._addParentTeardownLogic(
         this.source || (config.useDeprecatedSynchronousErrorHandling && !sink.syncErrorThrowable) ?
         this._subscribe(sink) :
         this._trySubscribe(sink)

src/internal/Subscriber.ts

@@ -1,6 +1,6 @@
 import { isFunction } from './util/isFunction';
 import { empty as emptyObserver } from './Observer';
-import { Observer, PartialObserver } from './types';
+import { Observer, PartialObserver, TeardownLogic } from './types';
 import { Subscription } from './Subscription';
 import { rxSubscriber as rxSubscriberSymbol } from '../internal/symbol/rxSubscriber';
 import { config } from './config';
@@ -47,6 +47,8 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
   protected isStopped: boolean = false;
   protected destination: PartialObserver<any>; // this `any` is the escape hatch to erase extra type param (e.g. R)
 
+  private _parentSubscription: Subscription | null = null;
+
   /**
    * @param {Observer|function(value: T): void} [destinationOrNext] A partially
    * defined Observer or a `next` callback function.
@@ -76,7 +78,7 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
             const trustedSubscriber = destinationOrNext[rxSubscriberSymbol]() as Subscriber<any>;
             this.syncErrorThrowable = trustedSubscriber.syncErrorThrowable;
             this.destination = trustedSubscriber;
-            trustedSubscriber.add(this);
+            trustedSubscriber._addParentTeardownLogic(this);
           } else {
             this.syncErrorThrowable = true;
             this.destination = new SafeSubscriber<T>(this, <PartialObserver<any>> destinationOrNext);
@@ -114,6 +116,7 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
     if (!this.isStopped) {
       this.isStopped = true;
       this._error(err);
+      this._unsubscribeParentSubscription();
     }
   }
 
@@ -127,6 +130,7 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
     if (!this.isStopped) {
       this.isStopped = true;
       this._complete();
+      this._unsubscribeParentSubscription();
     }
   }
 
@@ -152,6 +156,18 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
     this.unsubscribe();
   }
 
+  /** @deprecated This is an internal implementation detail, do not use. */
+  _addParentTeardownLogic(parentTeardownLogic: TeardownLogic) {
+    this._parentSubscription = this.add(parentTeardownLogic);
+  }
+
+  /** @deprecated This is an internal implementation detail, do not use. */
+  _unsubscribeParentSubscription() {
+    if (this._parentSubscription !== null) {
+      this._parentSubscription.unsubscribe();
+    }
+  }
+
   /** @deprecated This is an internal implementation detail, do not use. */
   _unsubscribeAndRecycle(): Subscriber<T> {
     const { _parent, _parents } = this;
@@ -162,6 +178,7 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
     this.isStopped = false;
     this._parent = _parent;
     this._parents = _parents;
+    this._parentSubscription = null;
     return this;
   }
 }

src/internal/observable/dom/WebSocketSubject.ts

@@ -276,9 +276,8 @@ export class WebSocketSubject<T> extends AnonymousSubject<T> {
     if (!this._socket) {
       this._connectSocket();
     }
-    let subscription = new Subscription();
-    subscription.add(this._output.subscribe(subscriber));
-    subscription.add(() => {
+    this._output.subscribe(subscriber);
+    subscriber.add(() => {
       const { _socket } = this;
       if (this._output.observers.length === 0) {
         if (_socket && _socket.readyState === 1) {
@@ -287,7 +286,7 @@ export class WebSocketSubject<T> extends AnonymousSubject<T> {
         this._resetState();
       }
     });
-    return subscription;
+    return subscriber;
   }
 
   unsubscribe() {

src/internal/testing/ColdObservable.ts

@@ -23,11 +23,12 @@ export class ColdObservable<T> extends Observable<T> implements SubscriptionLogg
     super(function (this: Observable<T>, subscriber: Subscriber<any>) {
       const observable: ColdObservable<T> = this as any;
       const index = observable.logSubscribedFrame();
-      subscriber.add(new Subscription(() => {
+      const subscription = new Subscription();
+      subscription.add(new Subscription(() => {
         observable.logUnsubscribedFrame(index);
       }));
       observable.scheduleMessages(subscriber);
-      return subscriber;
+      return subscription;
     });
     this.scheduler = scheduler;
   }

src/internal/testing/HotObservable.ts

@@ -28,10 +28,12 @@ export class HotObservable<T> extends Subject<T> implements SubscriptionLoggable
   _subscribe(subscriber: Subscriber<any>): Subscription {
     const subject: HotObservable<T> = this;
     const index = subject.logSubscribedFrame();
-    subscriber.add(new Subscription(() => {
+    const subscription = new Subscription();
+    subscription.add(new Subscription(() => {
       subject.logUnsubscribedFrame(index);
     }));
-    return super._subscribe(subscriber);
+    subscription.add(super._subscribe(subscriber));
+    return subscription;
   }
 
   setup() {