`ActiveJob::Base#queue_adapter` is now a `class_attribute`

This allows different `queue_adapters` to be used in each `ActiveJob`
class heirarchy. Previously, all subclasses used a single global queue
adapter.

2 files changed, 46 insertions, 5 deletions

diff --git a/activejob/test/cases/queue_adapter_test.rb b/activejob/test/cases/queue_adapter_test.rb
index d801a0852c..fb3fdc392f 100644
--- a/activejob/test/cases/queue_adapter_test.rb
+++ b/activejob/test/cases/queue_adapter_test.rb
@@ -1,5 +1,19 @@
 require 'helper'
 
+module ActiveJob
+  module QueueAdapters
+    class StubOneAdapter
+      def enqueue(*); end
+      def enqueue_at(*); end
+    end
+
+    class StubTwoAdapter
+      def enqueue(*); end
+      def enqueue_at(*); end
+    end
+  end
+end
+
 class QueueAdapterTest < ActiveJob::TestCase
   test 'should forbid nonsense arguments' do
     assert_raises(ArgumentError) { ActiveJob::Base.queue_adapter = Mutex }
@@ -12,13 +26,31 @@ class QueueAdapterTest < ActiveJob::TestCase
         'fake'
       end
 
-      def enqueue(*)
-      end
-
-      def enqueue_at(*)
-      end
+      def enqueue(*); end
+      def enqueue_at(*); end
     end
 
     assert_deprecated { ActiveJob::Base.queue_adapter = klass }
   end
+
+  test 'should allow overriding the queue_adapter at the child class level without affecting the parent or its sibling' do
+    base_queue_adapter = ActiveJob::Base.queue_adapter
+
+    child_job_one = Class.new(ActiveJob::Base)
+    child_job_one.queue_adapter = :stub_one
+
+    assert_not_equal ActiveJob::Base.queue_adapter, child_job_one.queue_adapter
+    assert_kind_of ActiveJob::QueueAdapters::StubOneAdapter, child_job_one.queue_adapter
+
+    child_job_two = Class.new(ActiveJob::Base)
+    child_job_two.queue_adapter = :stub_two
+
+    assert_kind_of ActiveJob::QueueAdapters::StubTwoAdapter, child_job_two.queue_adapter
+    assert_kind_of ActiveJob::QueueAdapters::StubOneAdapter, child_job_one.queue_adapter, "child_job_one's queue adapter should remain unchanged"
+    assert_equal base_queue_adapter, ActiveJob::Base.queue_adapter, "ActiveJob::Base's queue adapter should remain unchanged"
+
+    child_job_three = Class.new(ActiveJob::Base)
+
+    assert_not_nil child_job_three.queue_adapter
+  end
 end
diff --git a/activejob/test/cases/test_case_test.rb b/activejob/test/cases/test_case_test.rb
index bd23878b23..0a3a20d5a0 100644
--- a/activejob/test/cases/test_case_test.rb
+++ b/activejob/test/cases/test_case_test.rb
@@ -4,6 +4,15 @@ require 'jobs/logging_job'
 require 'jobs/nested_job'
 
 class ActiveJobTestCaseTest < ActiveJob::TestCase
+  # this tests that this job class doesn't get its adapter set.
+  # that's the correct behaviour since we don't want to break
+  # the `class_attribute` inheritence
+  class TestClassAttributeInheritenceJob < ActiveJob::Base
+    def self.queue_adapter=(*)
+      raise 'Attemping to break `class_attribute` inheritence, bad!'
+    end
+  end
+
   def test_include_helper
     assert_includes self.class.ancestors, ActiveJob::TestHelper
   end