Make Consumer queue opt optional

The queue name might be set dynamically in `handle_setup` instead of
supplying the value on start. If there is no queue name by the time we
start consuming then stop the server.

lib/rabbit/consumer/server.ex

@@ -9,7 +9,7 @@ defmodule Rabbit.Consumer.Server do
 
   @opts_schema %{
     connection: [type: [:tuple, :pid, :atom], required: true],
-    queue: [type: :binary, required: true],
+    queue: [type: :binary, required: false],
     prefetch_count: [type: :integer, default: 1],
     prefetch_size: [type: :integer, default: 0],
     consumer_tag: [type: :binary, default: ""],
@@ -91,6 +91,7 @@ defmodule Rabbit.Consumer.Server do
   def handle_continue(:consume, state) do
     case consume(state) do
       {:ok, state} -> {:noreply, state}
+      {:error, :no_queue_given} -> {:stop, :no_queue_given, state}
       {:error, state} -> {:noreply, state, {:continue, :restart_delay}}
     end
   end
@@ -239,6 +240,7 @@ defmodule Rabbit.Consumer.Server do
   end
 
   defp consume(%{consuming: true} = state), do: {:ok, state}
+  defp consume(%{queue: nil}), do: {:error, :no_queue_given}
 
   defp consume(state) do
     with :ok <- AMQP.Basic.qos(state.channel, state.qos_opts),

test/consumer_test.exs

@@ -203,6 +203,14 @@ defmodule Rabbit.ConsumerTest do
     assert {:ok, _, _} = start_consumer(MinimalTestConsumer, meta, queue: queue)
   end
 
+  test "stops the server if the queue is not specified", meta do
+    Process.flag(:trap_exit, true)
+    {:ok, consumer} = Consumer.start_link(MinimalTestConsumer, connection: meta.connection)
+    Process.monitor(consumer)
+
+    assert_receive {:EXIT, _pid, :no_queue_given}
+  end
+
   test "will ack messages based on return value", meta do
     state = connection_state(meta.connection)
     {:ok, channel} = AMQP.Channel.open(state.connection)