[#2173] Fix regression that let HttpRequestDecoder fail if the websocket response and a websocketframe are send in one go

codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectDecoder.java

@@ -362,8 +362,14 @@ public abstract class HttpObjectDecoder extends ReplayingDecoder<HttpObjectDecod
             break;
         }
         case UPGRADED: {
-            // Do not touch anything read - other handler will replace this codec with the upgraded protocol codec to
+            int readableBytes = actualReadableBytes();
-            // take the trafic over.
+            if (readableBytes > 0) {
+                // Keep on consuming as otherwise we may trigger an DecoderException,
+                // other handler will replace this codec with the upgraded protocol codec to
+                // take the traffic over at some point then.
+                // See https://github.com/netty/netty/issues/2173
+                out.add(buffer.readBytes(actualReadableBytes()));
+            }
             break;
         }
         }

codec-http/src/test/java/io/netty/handler/codec/http/HttpResponseDecoderTest.java

@@ -478,6 +478,33 @@ public class HttpResponseDecoderTest {
         assertThat(ch.readInbound(), is(nullValue()));
     }
 
+    // See https://github.com/netty/netty/issues/2173
+    @Test
+    public void testWebSocketResponseWithDataFollowing() {
+        byte[] data = ("HTTP/1.1 101 WebSocket Protocol Handshake\r\n" +
+                "Upgrade: WebSocket\r\n" +
+                "Connection: Upgrade\r\n" +
+                "Sec-WebSocket-Origin: http://localhost:8080\r\n" +
+                "Sec-WebSocket-Location: ws://localhost/some/path\r\n" +
+                "\r\n" +
+                "1234567812345678").getBytes();
+        byte[] otherData = {1, 2, 3, 4};
+
+        EmbeddedChannel ch = new EmbeddedChannel(new HttpResponseDecoder());
+        ch.writeInbound(Unpooled.wrappedBuffer(data, otherData));
+
+        HttpResponse res = (HttpResponse) ch.readInbound();
+        assertThat(res.getProtocolVersion(), sameInstance(HttpVersion.HTTP_1_1));
+        assertThat(res.getStatus(), is(HttpResponseStatus.SWITCHING_PROTOCOLS));
+        HttpContent content = (HttpContent) ch.readInbound();
+        assertThat(content.content().readableBytes(), is(16));
+        content.release();
+
+        assertThat(ch.finish(), is(true));
+
+        assertEquals(ch.readInbound(), Unpooled.wrappedBuffer(otherData));
+    }
+
     @Test
     public void testGarbageHeaders() {
         // A response without headers - from https://github.com/netty/netty/issues/2103