New H2 stream promise may never complete (#10443)

Motivation:

`Http2StreamChannelBootstrap#open0` invokes
`Http2MultiplexHandler#newOutboundStream()` which may throw an
`IllegalStateException`. In this case, it will never complete
the passed promise.

Modifications:

- `try-catch` all invocations of `newOutboundStream()` and fail
promise in case of any exception;

Result:

New H2 stream promise always completes.

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2StreamChannelBootstrap.java

@@ -168,10 +168,15 @@ public final class Http2StreamChannelBootstrap {
             return;
         }
         final Http2StreamChannel streamChannel;
-        if (ctx.handler() instanceof Http2MultiplexCodec) {
-            streamChannel = ((Http2MultiplexCodec) ctx.handler()).newOutboundStream();
-        } else {
-            streamChannel = ((Http2MultiplexHandler) ctx.handler()).newOutboundStream();
+        try {
+            if (ctx.handler() instanceof Http2MultiplexCodec) {
+                streamChannel = ((Http2MultiplexCodec) ctx.handler()).newOutboundStream();
+            } else {
+                streamChannel = ((Http2MultiplexHandler) ctx.handler()).newOutboundStream();
+            }
+        } catch (Exception e) {
+            promise.setFailure(e);
+            return;
         }
         try {
             init(streamChannel);

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2StreamChannelBootstrapTest.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.http2;
+
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandler;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.util.concurrent.DefaultPromise;
+import io.netty.util.concurrent.EventExecutor;
+import io.netty.util.concurrent.Promise;
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.junit.Assert.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class Http2StreamChannelBootstrapTest {
+
+    @Test
+    public void open0FailsPromiseOnHttp2MultiplexHandlerError() {
+        Http2StreamChannelBootstrap bootstrap = new Http2StreamChannelBootstrap(mock(Channel.class));
+
+        Http2MultiplexHandler handler = new Http2MultiplexHandler(mock(ChannelHandler.class));
+        EventExecutor executor = mock(EventExecutor.class);
+        when(executor.inEventLoop()).thenReturn(true);
+        ChannelHandlerContext ctx = mock(ChannelHandlerContext.class);
+        when(ctx.executor()).thenReturn(executor);
+        when(ctx.handler()).thenReturn(handler);
+
+        Promise<Http2StreamChannel> promise = new DefaultPromise(mock(EventExecutor.class));
+        bootstrap.open0(ctx, promise);
+        assertThat(promise.isDone(), is(true));
+        assertThat(promise.cause(), is(instanceOf(IllegalStateException.class)));
+    }
+}