[michaelklishin]

References rabbitmq/rabbitmq-server#17734.

[eglitobias]

Good morning @michaelklishin, Thank you! Looks good.

One suggestion: Maybe add a small integration spec that checks the channel is still usable after a server-sent basic.cancel. With the 4.2/4.3 CI matrix it would cover both the capability guard and the hand-packed frame. Something like:

context "with a server-sent basic.cancel" do
  let(:queue_name) { "basic.consume#{rand}" }

  it "keeps the channel usable" do
    cancellations = Thread::Queue.new

    ch = connection.create_channel
    q  = ch.durable_queue(queue_name, Bunny::Queue::Types::QUORUM)
    q.subscribe(on_cancellation: Proc.new { |*| cancellations << true })

    connection.with_channel { |ch2| ch2.queue_delete(queue_name) }

    expect(cancellations.pop(timeout: 5)).to eq true
    expect { ch.basic_qos(10) }.not_to raise_error
    expect(ch).to be_open
  end
end

I ran it locally against 4.2.9, 4.3.6 and today's v4.3.x nightly (4.3.6 doesn't advertise accept_consumer_cancel_ok yet, so only the nightly exercises the send path). It passes on all three, and fails on 4.2 without the capability check and on the nightly with a broken frame.