Fix a bug where HttpObjectDecoder generates two LastHttpContent conse…

…cutively

Motivation:
When an HttpResponseDecoder decodes an invalid chunk, a LastHttpContent instance is produced and the decoder enters the 'BAD_MESSAGE' state, which is not supposed to produce a message any further.  However, because HttpObjectDecoder.invalidChunk() did not clear this.message out to null, decodeLast() will produce another LastHttpContent message on a certain situation.

Modification:
Do not forget to null out HttpObjectDecoder.message in invalidChunk(), and add a test case for it.

Result:
No more consecutive LastHttpContent messages produced by HttpObjectDecoder.

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

@@ -470,6 +470,7 @@ private HttpContent invalidChunk(Exception cause) {
         checkpoint(State.BAD_MESSAGE);
         HttpContent chunk = new DefaultLastHttpContent(Unpooled.EMPTY_BUFFER);
         chunk.setDecoderResult(DecoderResult.failure(cause));
+        message = null;
         return chunk;
     }
 

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

@@ -536,4 +536,32 @@ public void testGarbageHeaders() {
         ch.finish();
         assertThat(ch.readInbound(), is(nullValue()));
     }
+
+
+    /**
+     * Tests if the decoder produces one and only {@link LastHttpContent} when an invalid chunk is received and
+     * the connection is closed.
+     */
+    @Test
+    public void testGarbageChunk() {
+        EmbeddedChannel channel = new EmbeddedChannel(new HttpResponseDecoder());
+        String responseWithIllegalChunk =
+                "HTTP/1.1 200 OK\r\n" +
+                "Transfer-Encoding: chunked\r\n\r\n" +
+                "NOT_A_CHUNK_LENGTH\r\n";
+
+        channel.writeInbound(Unpooled.copiedBuffer(responseWithIllegalChunk, CharsetUtil.US_ASCII));
+        assertThat(channel.readInbound(), is(instanceOf(HttpResponse.class)));
+
+        // Ensure that the decoder generates the last chunk with correct decoder result.
+        LastHttpContent invalidChunk = channel.readInbound();
+        assertThat(invalidChunk.getDecoderResult().isFailure(), is(true));
+        invalidChunk.release();
+
+        // And no more messages should be produced by the decoder.
+        assertThat(channel.readInbound(), is(nullValue()));
+
+        // .. even after the connection is closed.
+        assertThat(channel.finish(), is(false));
+    }
 }