FlowableWithLatestFrom forgets request (#5494)

* FlowableWithLatestFrom forgets request

* Add unit test and correct testBackpressure

* Revert indentation change

* Revert import change

Author: matgabriel

src/main/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFrom.java

@@ -81,6 +81,8 @@ public void onNext(T t) {
                     return;
                 }
                 actual.onNext(r);
+            } else{
+                request(1);
             }
         }
 

src/test/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFromTest.java

@@ -261,7 +261,7 @@ public void testNoDownstreamUnsubscribe() {
 
     @Test
     public void testBackpressure() {
-        Flowable<Integer> source = Flowable.range(1, 10);
+        PublishProcessor<Integer> source = PublishProcessor.create();
         PublishProcessor<Integer> other = PublishProcessor.create();
 
         Flowable<Integer> result = source.withLatestFrom(other, COMBINER);
@@ -274,17 +274,24 @@ public void testBackpressure() {
 
         ts.request(1);
 
+        source.onNext(1);
+
         assertTrue("Other has no observers!", other.hasSubscribers());
 
         ts.assertNoValues();
 
         other.onNext(1);
 
-        ts.request(1);
+        source.onNext(2);
 
         ts.assertValue((2 << 8) + 1);
 
         ts.request(5);
+        source.onNext(3);
+        source.onNext(4);
+        source.onNext(5);
+        source.onNext(6);
+        source.onNext(7);
         ts.assertValues(
                 (2 << 8) + 1, (3 << 8) + 1, (4 << 8) + 1, (5 << 8) + 1,
                 (6 << 8) + 1, (7 << 8) + 1
@@ -717,4 +724,30 @@ public void zeroOtherCombinerReturnsNull() {
         .test()
         .assertFailureAndMessage(NullPointerException.class, "The combiner returned a null value");
     }
+
+    @Test
+    public void testSingleRequestNotForgottenWhenNoData() {
+        PublishProcessor<Integer> source = PublishProcessor.create();
+        PublishProcessor<Integer> other = PublishProcessor.create();
+
+        Flowable<Integer> result = source.withLatestFrom(other, COMBINER);
+
+        TestSubscriber<Integer> ts = new TestSubscriber<Integer>(0L);
+
+        result.subscribe(ts);
+
+        ts.request(1);
+
+        source.onNext(1);
+
+        ts.assertNoValues();
+
+        other.onNext(1);
+
+        ts.assertNoValues();
+
+        source.onNext(2);
+
+        ts.assertValue((2 << 8) + 1);
+    }
 }