2.x: fix Flowable.concatMapEager hang due to bad request management (#4751)

* 2.x: fix Flowable.concatMapEager hang due to bad request management

* Missed negation of check

Author: akarnokd

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

@@ -233,12 +233,11 @@ public void drain() {
             int missed = 1;
             InnerQueuedSubscriber<R> inner = current;
             Subscriber<? super R> a = actual;
-            long r = requested.get();
-            long e = 0L;
             ErrorMode em = errorMode;
 
-            outer:
             for (;;) {
+                long r = requested.get();
+                long e = 0L;
 
                 if (inner == null) {
 
@@ -271,6 +270,8 @@ public void drain() {
                     }
                 }
 
+                boolean continueNextSource = false;
+
                 if (inner != null) {
                     SimpleQueue<R> q = inner.queue();
                     if (q != null) {
@@ -313,7 +314,8 @@ public void drain() {
                                 inner = null;
                                 current = null;
                                 s.request(1);
-                                continue outer;
+                                continueNextSource = true;
+                                break;
                             }
 
                             if (empty) {
@@ -353,15 +355,18 @@ public void drain() {
                                 inner = null;
                                 current = null;
                                 s.request(1);
-                                continue;
+                                continueNextSource = true;
                             }
                         }
                     }
                 }
 
                 if (e != 0L && r != Long.MAX_VALUE) {
-                    r = requested.addAndGet(-e);
-                    e = 0L;
+                    requested.addAndGet(-e);
+                }
+
+                if (continueNextSource) {
+                    continue;
                 }
 
                 missed = addAndGet(-missed);

src/main/java/io/reactivex/internal/subscribers/InnerQueuedSubscriber.java

@@ -72,14 +72,14 @@ public void onSubscribe(Subscription s) {
                 if (m == QueueSubscription.ASYNC) {
                     fusionMode = m;
                     queue = qs;
-                    QueueDrainHelper.request(get(), prefetch);
+                    QueueDrainHelper.request(s, prefetch);
                     return;
                 }
             }
 
             queue = QueueDrainHelper.createQueue(prefetch);
 
-            QueueDrainHelper.request(get(), prefetch);
+            QueueDrainHelper.request(s, prefetch);
         }
     }
 
@@ -104,22 +104,26 @@ public void onComplete() {
 
     @Override
     public void request(long n) {
-        long p = produced + n;
-        if (p >= limit) {
-            produced = 0L;
-            get().request(p);
-        } else {
-            produced = p;
+        if (fusionMode != QueueSubscription.SYNC) {
+            long p = produced + n;
+            if (p >= limit) {
+                produced = 0L;
+                get().request(p);
+            } else {
+                produced = p;
+            }
         }
     }
 
     public void requestOne() {
-        long p = produced + 1;
-        if (p == limit) {
-            produced = 0L;
-            get().request(p);
-        } else {
-            produced = p;
+        if (fusionMode != QueueSubscription.SYNC) {
+            long p = produced + 1;
+            if (p == limit) {
+                produced = 0L;
+                get().request(p);
+            } else {
+                produced = p;
+            }
         }
     }
 

src/test/java/io/reactivex/TestHelper.java

@@ -30,6 +30,7 @@
 import io.reactivex.disposables.*;
 import io.reactivex.exceptions.*;
 import io.reactivex.functions.*;
+import io.reactivex.internal.functions.ObjectHelper;
 import io.reactivex.internal.fuseable.*;
 import io.reactivex.internal.operators.maybe.MaybeToFlowable;
 import io.reactivex.internal.operators.single.SingleToFlowable;
@@ -144,21 +145,25 @@ public void accept(Throwable t) {
     }
 
     public static void assertError(List<Throwable> list, int index, Class<? extends Throwable> clazz) {
-        try {
-            assertTrue(list.get(index).toString(), clazz.isInstance(list.get(index)));
-        } catch (AssertionError e) {
-            list.get(index).printStackTrace();
-            throw e;
+        Throwable ex = list.get(index);
+        if (!clazz.isInstance(ex)) {
+            AssertionError err = new AssertionError(clazz + " expected but got " + list.get(index));
+            err.initCause(list.get(index));
+            throw err;
         }
     }
 
     public static void assertError(List<Throwable> list, int index, Class<? extends Throwable> clazz, String message) {
-        try {
-            assertTrue(list.get(index).toString(), clazz.isInstance(list.get(index)));
-            assertEquals(message, list.get(index).getMessage());
-        } catch (AssertionError e) {
-            list.get(index).printStackTrace();
-            throw e;
+        Throwable ex = list.get(index);
+        if (!clazz.isInstance(ex)) {
+            AssertionError err = new AssertionError("Type " + clazz + " expected but got " + ex);
+            err.initCause(ex);
+            throw err;
+        }
+        if (!ObjectHelper.equals(message, ex.getMessage())) {
+            AssertionError err = new AssertionError("Message " + message + " expected but got " + ex.getMessage());
+            err.initCause(ex);
+            throw err;
         }
     }
 

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

@@ -577,11 +577,12 @@ public void testAsynchronousRun() {
             public Flowable<Integer> apply(Integer t) {
                 return Flowable.range(1, 1000).subscribeOn(Schedulers.computation());
             }
-        }).observeOn(Schedulers.newThread()).subscribe(ts);
-
-        ts.awaitTerminalEvent(5, TimeUnit.SECONDS);
-        ts.assertNoErrors();
-        ts.assertValueCount(2000);
+        }).observeOn(Schedulers.single())
+        .test()
+        .awaitDone(5, TimeUnit.SECONDS)
+        .assertNoErrors()
+        .assertValueCount(2000)
+        .assertComplete();
     }
 
     @Test