fix(multiple-consume): only send consume message once

Previously if multiple attempts to call consume were made, then
QAmqpQueue would send a frame for each of them leading to multiple
consumer tags and general confusion. This guards from calling
consume multiple times.

src/qamqpqueue.cpp

@@ -17,7 +17,8 @@ QAmqpQueuePrivate::QAmqpQueuePrivate(QAmqpQueue *q)
       delayedDeclare(false),
       declared(false),
       recievingMessage(false),
-      consuming(false)
+      consuming(false),
+      consumeRequested(false)
 {
 }
 
@@ -218,6 +219,7 @@ void QAmqpQueuePrivate::consumeOk(const QAmqpMethodFrame &frame)
     consumerTag = QAmqpFrame::readAmqpField(stream, QAmqpMetaType::ShortString).toString();
     qAmqpDebug("consumer tag = %s", qPrintable(consumerTag));
     consuming = true;
+    consumeRequested = false;
     Q_EMIT q->consuming(consumerTag);
 }
 
@@ -273,6 +275,8 @@ void QAmqpQueuePrivate::cancelOk(const QAmqpMethodFrame &frame)
     }
 
     consumerTag.clear();
+    consuming = false;
+    consumeRequested = false;
     Q_EMIT q->cancelled(consumer);
 }
 
@@ -445,6 +449,11 @@ bool QAmqpQueue::consume(int options)
         return false;
     }
 
+    if (d->consumeRequested) {
+        qAmqpDebug() << Q_FUNC_INFO << "already attempting to consume";
+        return false;
+    }
+
     if (d->consuming) {
         qAmqpDebug() << Q_FUNC_INFO << "already consuming with tag: " << d->consumerTag;
         return false;
@@ -465,6 +474,7 @@ bool QAmqpQueue::consume(int options)
 
     frame.setArguments(arguments);
     d->sendFrame(frame);
+    d->consumeRequested = true;
     return true;
 }
 

src/qamqpqueue_p.h

@@ -50,6 +50,7 @@ public:
     bool recievingMessage;
     QAmqpMessage currentMessage;
     bool consuming;
+    bool consumeRequested;
 
     Q_DECLARE_PUBLIC(QAmqpQueue)
 

tests/auto/qamqpqueue/tst_qamqpqueue.cpp

@@ -4,6 +4,7 @@
 
 #include <QtTest/QtTest>
 #include "qamqptestcase.h"
+#include "signalspy.h"
 
 #include "qamqpclient.h"
 #include "qamqpqueue.h"
@@ -33,6 +34,7 @@ private Q_SLOTS:
     void delayedBind();
     void purge();
     void canOnlyStartConsumingOnce();
+    void ensureConsumeOnlySentOnce();
     void cancel();
     void invalidCancelBecauseNotConsuming();
     void invalidCancelBecauseInvalidConsumerTag();
@@ -346,10 +348,29 @@ void tst_QAMQPQueue::purge()
 void tst_QAMQPQueue::canOnlyStartConsumingOnce()
 {
     QAmqpQueue *queue = client->createQueue("test-single-consumer");
+    QSignalSpy spy(queue, SIGNAL(consuming(QString)));
     declareQueueAndVerifyConsuming(queue);
     QCOMPARE(queue->consume(), false);
 }
 
+void tst_QAMQPQueue::ensureConsumeOnlySentOnce()
+{
+    QAmqpQueue *queue = client->createQueue("test-single-consumer");
+    SignalSpy spy(queue, SIGNAL(consuming(QString)));
+    queue->declare();
+    QVERIFY(waitForSignal(queue, SIGNAL(declared())));
+
+    // try to consume twice
+    QVERIFY(queue->consume());
+    QCOMPARE(queue->consume(), false);
+    QVERIFY(spy.wait());
+    QCOMPARE(spy.size(), 1);
+
+    // clean up queue
+    queue->remove(QAmqpQueue::roForce);
+    QVERIFY(waitForSignal(queue, SIGNAL(removed())));
+}
+
 void tst_QAMQPQueue::cancel()
 {
     QAmqpQueue *queue = client->createQueue("test-cancel");