fix: removing delivery attempt attribute when dead lettering is not enabled

google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/MessageDispatcher.java

@@ -346,10 +346,16 @@ private void processBatch(List<OutstandingMessage> batch) {
   }
 
   private PubsubMessage addDeliveryInfoCount(ReceivedMessage receivedMessage) {
-    return PubsubMessage.newBuilder(receivedMessage.getMessage())
-        .putAttributes(
-            "googclient_deliveryattempt", Integer.toString(receivedMessage.getDeliveryAttempt()))
-        .build();
+    PubsubMessage originalMessage = receivedMessage.getMessage();
+    int deliveryAttempt = receivedMessage.getDeliveryAttempt();
+    // Delivery Attempt will be set to 0 if DeadLetterPolicy is not set on the subscription. In
+    // this case, do not populate the PubsubMessage with the delivery attempt attribute.
+    if (deliveryAttempt > 0) {
+      return PubsubMessage.newBuilder(originalMessage)
+          .putAttributes("googclient_deliveryattempt", Integer.toString(deliveryAttempt))
+          .build();
+    }
+    return originalMessage;
   }
 
   private void processOutstandingMessage(final PubsubMessage message, final AckHandler ackHandler) {

google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Subscriber.java

@@ -207,8 +207,11 @@ public static Builder newBuilder(String subscription, MessageReceiver receiver)
   }
 
   /** Returns the delivery attempt count for a received {@link PubsubMessage} */
-  public static int getDeliveryAttempt(PubsubMessage message) {
-    return Integer.parseInt(message.getAttributesOrDefault("googclient_deliveryattempt", "0"));
+  public static Integer getDeliveryAttempt(PubsubMessage message) {
+    if (!message.containsAttributes("googclient_deliveryattempt")) {
+      return null;
+    }
+    return Integer.parseInt(message.getAttributesOrThrow("googclient_deliveryattempt"));
   }
 
   /** Subscription which the subscriber is subscribed to. */

google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/SubscriberTest.java

@@ -86,15 +86,16 @@ public void tearDown() throws Exception {
 
   @Test
   public void testDeliveryAttemptHelper() {
-    int deliveryAttempt = 3;
+    Integer deliveryAttempt = 3;
     PubsubMessage message =
         PubsubMessage.newBuilder()
             .putAttributes("googclient_deliveryattempt", Integer.toString(deliveryAttempt))
             .build();
     assertEquals(Subscriber.getDeliveryAttempt(message), deliveryAttempt);
 
+    // In the case where delivery attempt attribute is not populated, expect null
     PubsubMessage emptyMessage = PubsubMessage.newBuilder().build();
-    assertEquals(Subscriber.getDeliveryAttempt(emptyMessage), 0);
+    assertEquals(Subscriber.getDeliveryAttempt(emptyMessage), null);
   }
 
   @Test