Do not suppress channelReadComplete() when a handler was just added

Related:
- 27a25e29f7

Motivation:

The commit mentioned above introduced a regression where
channelReadComplete() event is swallowed by a handler which was added
dynamically.

Modifications:

Do not suppress channelReadComplete() if the current handler's
channelRead() method was not invoked at all, so that a just-added
handler does not suppress channelReadComplete().

Result:

Regression is gone, and channelReadComplete() is invoked when necessary.

codec/src/main/java/io/netty/handler/codec/ByteToMessageDecoder.java

@@ -200,11 +200,11 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
             ByteBuf bytes = buf.readBytes(readable);
             buf.release();
             ctx.fireChannelRead(bytes);
+            ctx.fireChannelReadComplete();
         } else {
             buf.release();
         }
         cumulation = null;
-        ctx.fireChannelReadComplete();
         handlerRemoved0(ctx);
     }
 

transport/src/main/java/io/netty/channel/AbstractChannelHandlerContext.java

@@ -36,13 +36,22 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
     private final DefaultChannelPipeline pipeline;
     private final String name;
 
+    /**
+     * Set when the {@link ChannelInboundHandler#channelRead(ChannelHandlerContext, Object)} of
+     * this context's handler is invoked.
+     * Cleared when a user calls {@link #fireChannelReadComplete()} on this context.
+     *
+     * See {@link #fireChannelReadComplete()} to understand how this flag is used.
+     */
+    boolean invokedThisChannelRead;
+
     /**
      * Set when a user calls {@link #fireChannelRead(Object)} on this context.
      * Cleared when a user calls {@link #fireChannelReadComplete()} on this context.
      *
      * See {@link #fireChannelReadComplete()} to understand how this flag is used.
      */
-    private volatile boolean firedChannelRead;
+    private volatile boolean invokedNextChannelRead;
 
     /**
      * Set when a user calls {@link #read()} on this context.
@@ -50,7 +59,7 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
      *
      * See {@link #fireChannelReadComplete()} to understand how this flag is used.
      */
-    private volatile boolean invokedRead;
+    private volatile boolean invokedPrevRead;
 
     /**
      * {@code true} if and only if this context has been removed from the pipeline.
@@ -174,7 +183,7 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
     public ChannelHandlerContext fireChannelRead(Object msg) {
         AbstractChannelHandlerContext next = findContextInbound();
         ReferenceCountUtil.touch(msg, next);
-        firedChannelRead = true;
+        invokedNextChannelRead = true;
         next.invoker().invokeChannelRead(next, msg);
         return this;
     }
@@ -187,11 +196,16 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
          *
          * This is pretty common for the handlers that transform multiple messages into one message,
          * such as byte-to-message decoder and message aggregators.
+         *
+         * Only one exception is when nobody invoked the channelRead() method of this context's handler.
+         * It means the handler has been added later dynamically.
          */
-        if (firedChannelRead) {
-            // The handler of this context produced a message, so we are OK to trigger this event.
-            firedChannelRead = false;
-            invokedRead = false;
+        if (invokedNextChannelRead ||  // The handler of this context produced a message, or
+            !invokedThisChannelRead) { // it is not required to produce a message to trigger the event.
+
+            invokedNextChannelRead = false;
+            invokedPrevRead = false;
+
             AbstractChannelHandlerContext next = findContextInbound();
             next.invoker().invokeChannelReadComplete(next);
             return this;
@@ -208,7 +222,7 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
          * Why? Because otherwise the next handler will not receive {@code channelRead()} nor
          * {@code channelReadComplete()} event at all for the {@link #read()} operation it issued.
          */
-        if (invokedRead && !channel().config().isAutoRead()) {
+        if (invokedPrevRead && !channel().config().isAutoRead()) {
             /**
              * The next (or upstream) handler invoked {@link #read()}, but it didn't get any
              * {@code channelRead()} event. We should read once more, so that the handler of the current
@@ -216,7 +230,7 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
              */
             read();
         } else {
-            invokedRead = false;
+            invokedPrevRead = false;
         }
 
         return this;
@@ -306,7 +320,7 @@ abstract class AbstractChannelHandlerContext implements ChannelHandlerContext, R
     @Override
     public ChannelHandlerContext read() {
         AbstractChannelHandlerContext next = findContextOutbound();
-        invokedRead = true;
+        invokedPrevRead = true;
         next.invoker().invokeRead(next);
         return this;
     }

transport/src/main/java/io/netty/channel/ChannelHandlerInvokerUtil.java

@@ -80,6 +80,7 @@ public final class ChannelHandlerInvokerUtil {
 
     public static void invokeChannelReadNow(final ChannelHandlerContext ctx, final Object msg) {
         try {
+            ((AbstractChannelHandlerContext) ctx).invokedThisChannelRead = true;
             ((ChannelInboundHandler) ctx.handler()).channelRead(ctx, msg);
         } catch (Throwable t) {
             notifyHandlerException(ctx, t);

transport/src/main/java/io/netty/channel/DefaultChannelPipeline.java

@@ -584,6 +584,7 @@ final class DefaultChannelPipeline implements ChannelPipeline {
 
     private void callHandlerAdded0(final AbstractChannelHandlerContext ctx) {
         try {
+            ctx.invokedThisChannelRead = false;
             ctx.handler().handlerAdded(ctx);
         } catch (Throwable t) {
             boolean removed = false;