onPartitionsAssigned fired without SeekPosition.BEGINNING/END

[dcheung2]

In what version(s) of Spring for Apache Kafka are you seeing this issue?

2.8.2

Describe the bug

When using a custom ContainerFactory that create ContainerProperties(TopicPartitionOffset)
with SeekPosition.END

ConsumerSeekAware.onPartitionsAssigned will receive an empty map.

To Reproduce

A custom ContainerFactory that does not use consumer group

       class BroadcastContainerFactory extends ConcurrentKafkaListenerContainerFactory{
   	protected ConcurrentMessageListenerContainer createContainerInstance(KafkaListenerEndpoint endpoint){
           var properties = new ContainerProperties(new TopicPartitionOffset("foo", 0, null, SeekPosition.END));
           return new ConcurrentMessageListenerContainer<>(getConsumerFactory(), properties);
        }
      }

Expected behavior

onPartitionsAssigned() should receive assignments that
either

• single map has an value of null
• or) single map has an value of actual offset

---

** Study **
I've inspected code in https://github.com/spring-projects/spring-kafka/blob/2.8.x/spring-kafka/src/main/java/org/springframework/kafka/listener/KafkaMessageListenerContainer.java#L2933
.

It is pass the same partitions map for doInitialSeeks and onPartitionsAssigned

Likely that using new TopicPartitionOffset("foo", 0, System.currentTimeMillis(), SeekPosition.TIMESTAMP) (for END)
new TopicPartitionOffset("foo", 0, 0, SeekPosition.TIMESTAMP) (for BEGINNING)
could workaround.