Errors being trapped by merge operations like switchMaps

RxJS version: 5.5.5

Code to reproduce:

EDIT: Ugh, the code I had to reproduce this didn’t reproduce it as expected… but I’ve seen a non-trivial reproduction. cc @IgorMinar

Expected behavior: Error “final error” should be reported in console

Actual behavior: Error is squeltched.

Additional information: This only happens if the observable in the merge operation is asynchronous. The error thrown by the subscription unwinds the stack back to the switchMap’s subscriber (via parent.notifyError from InnerSubscriber), and it’s swallowed because the switchMap subscriber isStopped.

[IgorMinar]

@jayphelps that build didn’t work because it’s not complete (all add/operator/* files are missing), but I was able to diff it and extract this patch that I applied to my current build:

--- node_modules/rxjs.patched/src/Subscriber.ts 2017-12-06 09:58:33.000000000 -0800
+++ node_modules/rxjs/src/Subscriber.ts 2017-12-05 01:29:16.000000000 -0800
@@ -68,6 +68,7 @@
         }
         if (typeof destinationOrNext === 'object') {
           if (destinationOrNext instanceof Subscriber) {
+            this.syncErrorThrowable = destinationOrNext.syncErrorThrowable;
             this.destination = (<Subscriber<any>> destinationOrNext);
             (<any> this.destination).add(this);
           } else {

--- node_modules/rxjs.patched/src/Observable.ts 2017-12-06 09:58:33.000000000 -0800
+++ node_modules/rxjs/src/Observable.ts 2017-12-05 01:29:16.000000000 -0800
@@ -199,7 +199,7 @@
     if (operator) {
       operator.call(sink, this.source);
     } else {
-      sink.add(this.source ? this._subscribe(sink) : this._trySubscribe(sink));
+      sink.add(this.source || !sink.syncErrorThrowable ? this._subscribe(sink) : this._trySubscribe(sink));
     }

     if (sink.syncErrorThrowable) {

With this patch applied to the JS files by hand, I was able to confirm that the errors now get propagated correctly, so if I extracted the change correctly, then what you did resolves the problem.

[lock[bot]]

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