Issue #3170 - fail the CompletableFuture if onOpen throws

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-websocket/websocket-core/src/main/java/org/eclipse/jetty/websocket/core/internal/WebSocketChannel.java

@@ -440,6 +440,13 @@ public class WebSocketChannel implements IncomingFrames, FrameHandler.CoreSessio
         catch (Throwable t)
         {
             openCallback.failed(t);
+
+            /*
+            This is double handling of the exception but we need to do this because we have two separate
+            mechanisms for returning the CoreSession, onOpen and the CompletableFuture and both the onOpen callback
+            and the CompletableFuture require the exception.
+             */
+            throw new RuntimeException(t);
         }
 
     }

jetty-websocket/websocket-core/src/test/java/org/eclipse/jetty/websocket/core/proxy/WebSocketProxyTest.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.net.URI;
 import java.time.Duration;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
@@ -57,6 +58,7 @@ import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 public class WebSocketProxyTest
 {
@@ -231,7 +233,8 @@ public class WebSocketProxyTest
         try (StacklessLogging stacklessLogging = new StacklessLogging(WebSocketChannel.class))
         {
             CompletableFuture<CoreSession> response = _client.connect(clientHandler, new URI("ws://localhost:8080/proxy/"));
-            response.get(5, TimeUnit.SECONDS);
+            Exception e = assertThrows(ExecutionException.class, ()->response.get(5, TimeUnit.SECONDS));
+            assertThat(e.getMessage(), containsString("simulated client onOpen error"));
             clientHandler.awaitClose();
             serverFrameHandler.awaitClose();
             awaitProxyClose(proxyClientSide, proxyServerSide);