adds class check for discarded values (rsocket#1091)

rsocket-core/src/main/java/io/rsocket/core/DefaultRSocketClient.java

@@ -46,13 +46,16 @@
  */
 class DefaultRSocketClient extends ResolvingOperator<RSocket>
     implements CoreSubscriber<RSocket>, CorePublisher<RSocket>, RSocketClient {
-  static final Consumer<ReferenceCounted> DISCARD_ELEMENTS_CONSUMER =
-      referenceCounted -> {
-        if (referenceCounted.refCnt() > 0) {
-          try {
-            referenceCounted.release();
-          } catch (IllegalReferenceCountException e) {
-            // ignored
+  static final Consumer<?> DISCARD_ELEMENTS_CONSUMER =
+      data -> {
+        if (data instanceof ReferenceCounted) {
+          ReferenceCounted referenceCounted = ((ReferenceCounted) data);
+          if (referenceCounted.refCnt() > 0) {
+            try {
+              referenceCounted.release();
+            } catch (IllegalReferenceCountException e) {
+              // ignored
+            }
           }
         }
       };

rsocket-core/src/main/java/io/rsocket/core/SendUtils.java

@@ -40,11 +40,13 @@
 final class SendUtils {
   private static final Consumer<?> DROPPED_ELEMENTS_CONSUMER =
       data -> {
-        try {
-          ReferenceCounted referenceCounted = (ReferenceCounted) data;
-          referenceCounted.release();
-        } catch (Throwable e) {
-          // ignored
+        if (data instanceof ReferenceCounted) {
+          try {
+            ReferenceCounted referenceCounted = (ReferenceCounted) data;
+            referenceCounted.release();
+          } catch (Throwable e) {
+            // ignored
+          }
         }
       };
 

rsocket-core/src/test/java/io/rsocket/core/DefaultRSocketClientTests.java

@@ -39,6 +39,7 @@
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.BiFunction;
+import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import org.assertj.core.api.Assertions;
@@ -49,6 +50,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.Mockito;
 import org.reactivestreams.Publisher;
 import reactor.core.Disposable;
 import reactor.core.publisher.Flux;
@@ -79,6 +81,26 @@ public void setUp() throws Throwable {
   public void tearDown() {
     Hooks.resetOnErrorDropped();
     Hooks.resetOnNextDropped();
+    rule.allocator.assertHasNoLeaks();
+  }
+
+  @Test
+  @SuppressWarnings("unchecked")
+  void discardElementsConsumerShouldAcceptOtherTypesThanReferenceCounted() {
+    Consumer discardElementsConsumer = DefaultRSocketClient.DISCARD_ELEMENTS_CONSUMER;
+    discardElementsConsumer.accept(new Object());
+  }
+
+  @Test
+  void droppedElementsConsumerReleaseReference() {
+    ReferenceCounted referenceCounted = Mockito.mock(ReferenceCounted.class);
+    Mockito.when(referenceCounted.release()).thenReturn(true);
+    Mockito.when(referenceCounted.refCnt()).thenReturn(1);
+
+    Consumer discardElementsConsumer = DefaultRSocketClient.DISCARD_ELEMENTS_CONSUMER;
+    discardElementsConsumer.accept(referenceCounted);
+
+    Mockito.verify(referenceCounted).release();
   }
 
   static Stream<Arguments> interactions() {

rsocket-core/src/test/java/io/rsocket/core/SendUtilsTest.java

@@ -0,0 +1,31 @@
+package io.rsocket.core;
+
+import static org.mockito.Mockito.*;
+
+import io.netty.util.ReferenceCounted;
+import java.util.function.Consumer;
+import org.junit.jupiter.api.Test;
+
+public class SendUtilsTest {
+
+  @Test
+  void droppedElementsConsumerShouldAcceptOtherTypesThanReferenceCounted() {
+    Consumer value = extractDroppedElementConsumer();
+    value.accept(new Object());
+  }
+
+  @Test
+  void droppedElementsConsumerReleaseReference() {
+    ReferenceCounted referenceCounted = mock(ReferenceCounted.class);
+    when(referenceCounted.release()).thenReturn(true);
+
+    Consumer value = extractDroppedElementConsumer();
+    value.accept(referenceCounted);
+
+    verify(referenceCounted).release();
+  }
+
+  private static Consumer<?> extractDroppedElementConsumer() {
+    return (Consumer<?>) SendUtils.DISCARD_CONTEXT.stream().findAny().get().getValue();
+  }
+}