From 2fbda3fda79ce6e4e6ff3b67a32d86719342ba4a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ingo=20B=C3=BCrk?= <ingo.buerk@tngtech.com>
Date: Mon, 7 May 2018 22:32:42 +0200
Subject: [PATCH] fix(delayWhen): Emit source value if duration selector
 completes synchronously

This fixes an issue where delayWhen would not re-emit a source emission if the duration selector
completed synchronously.

fixes #3663
---
 spec/operators/delayWhen-spec.ts    | 23 +++++++++++++++++++++++
 src/internal/operators/delayWhen.ts |  9 +--------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/spec/operators/delayWhen-spec.ts b/spec/operators/delayWhen-spec.ts
index 35bdb76f7d2..a2094124f51 100644
--- a/spec/operators/delayWhen-spec.ts
+++ b/spec/operators/delayWhen-spec.ts
@@ -1,6 +1,7 @@
 import * as Rx from 'rxjs/Rx';
 import { hot, cold, expectObservable, expectSubscriptions } from '../helpers/marble-testing';
 import { expect } from 'chai';
+import { EMPTY } from 'rxjs';
 
 declare function asDiagram(arg: string): Function;
 
@@ -104,6 +105,28 @@ describe('Observable.prototype.delayWhen', () => {
     expectObservable(result).toBe(expected);
     expectSubscriptions(e1.subscriptions).toBe(subs);
     expectSubscriptions(selector.subscriptions).toBe(selectorSubs);
+    });
+
+  it('should emit if the selector completes synchronously', () => {
+    const e1 =        hot('a--|');
+    const expected =      'a--|';
+    const subs =          '^  !';
+
+    const result = e1.delayWhen((x: any) => EMPTY);
+
+    expectObservable(result).toBe(expected);
+    expectSubscriptions(e1.subscriptions).toBe(subs);
+  });
+
+  it('should emit if the source completes synchronously and the selector completes synchronously', () => {
+    const e1 =        hot('(a|)');
+    const expected =      '(a|)';
+    const subs =          '(^!)';
+
+    const result = e1.delayWhen((x: any) => EMPTY);
+
+    expectObservable(result).toBe(expected);
+    expectSubscriptions(e1.subscriptions).toBe(subs);
   });
 
   it('should not emit if selector never emits', () => {
diff --git a/src/internal/operators/delayWhen.ts b/src/internal/operators/delayWhen.ts
index f2c0d4a702f..ef7e834f0f8 100644
--- a/src/internal/operators/delayWhen.ts
+++ b/src/internal/operators/delayWhen.ts
@@ -79,7 +79,6 @@ class DelayWhenOperator<T> implements Operator<T, T> {
 class DelayWhenSubscriber<T, R> extends OuterSubscriber<T, R> {
   private completed: boolean = false;
   private delayNotifierSubscriptions: Array<Subscription> = [];
-  private values: Array<T> = [];
 
   constructor(destination: Subscriber<T>,
               private delayDurationSelector: (value: T) => Observable<any>) {
@@ -126,15 +125,11 @@ class DelayWhenSubscriber<T, R> extends OuterSubscriber<T, R> {
     subscription.unsubscribe();
 
     const subscriptionIdx = this.delayNotifierSubscriptions.indexOf(subscription);
-    let value: T = null;
-
     if (subscriptionIdx !== -1) {
-      value = this.values[subscriptionIdx];
       this.delayNotifierSubscriptions.splice(subscriptionIdx, 1);
-      this.values.splice(subscriptionIdx, 1);
     }
 
-    return value;
+    return subscription.outerValue;
   }
 
   private tryDelay(delayNotifier: Observable<any>, value: T): void {
@@ -144,8 +139,6 @@ class DelayWhenSubscriber<T, R> extends OuterSubscriber<T, R> {
       this.add(notifierSubscription);
       this.delayNotifierSubscriptions.push(notifierSubscription);
     }
-
-    this.values.push(value);
   }
 
   private tryComplete(): void {