ConfirmListener#handleNack() can not be triggered

[leopardrota]

Describe the bug

When a message is unable to reach any queue(exchange is right, routingKey is wrong), ConfirmListener#handleNack() can not be triggered and ConfirmListener#handleAck() is always be invoked.

Reproduction steps

server: 3.8.3
com.rabbimq:amqp-client:5.16.0

1.channel.confirmSelect();
channel.addConfirmListener(new MyConfirmListener());

2.channel.basicPublish(exchange, routingKey, props, data); //exchange is right, routingKey is wrong

Expected behavior

ConfirmListener#handleNack() can be triggered not ConfirmListener#handleAck()

Additional context

Currently, the message can not reach any queue, but ConfirmListener#handleAck() can be invoked. So where does the message go? Is it directly discarded?

[michaelklishin]

A couple of things.

1. Your expectation about when a negative publisher acknowledgement (confirm) is sent is off: it will not be sent when the message cannot be routed. For that, see mandatory routing and returned messages. basic.nack will be sent when the queue process cannot accept an ingress message (due to a failure of some kind, a lack of quorum, things like that: nothing to do with routing, as this happens after the routing step)
2. RabbitMQ 3.8 has reached end of life in July 2022