`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, 36 insertions, 12 deletions

diff --git a/activejob/lib/active_job/queue_adapter.rb b/activejob/lib/active_job/queue_adapter.rb
index 23b5f7de75..f3a3d27193 100644
--- a/activejob/lib/active_job/queue_adapter.rb
+++ b/activejob/lib/active_job/queue_adapter.rb
@@ -1,4 +1,5 @@
 require 'active_job/queue_adapters/inline_adapter'
+require 'active_support/core_ext/class/attribute'
 require 'active_support/core_ext/string/inflections'
 
 module ActiveJob
@@ -7,34 +8,45 @@ module ActiveJob
   module QueueAdapter #:nodoc:
     extend ActiveSupport::Concern
 
+    included do
+      class_attribute :_queue_adapter, instance_accessor: false, instance_predicate: false
+      self.queue_adapter = :inline
+    end
+
     # Includes the setter method for changing the active queue adapter.
     module ClassMethods
-      mattr_reader(:queue_adapter) { ActiveJob::QueueAdapters::InlineAdapter }
+      def queue_adapter
+        _queue_adapter
+      end
 
       # Specify the backend queue provider. The default queue adapter
       # is the :inline queue. See QueueAdapters for more
       # information.
       def queue_adapter=(name_or_adapter_or_class)
+        self._queue_adapter = interpret_adapter(name_or_adapter_or_class)
+      end
+
+      private
+
+      def interpret_adapter(name_or_adapter_or_class)
         case name_or_adapter_or_class
         when Symbol, String
-          self.queue_adapter = load_adapter(name_or_adapter_or_class)
+          load_adapter(name_or_adapter_or_class)
         else
-          @@queue_adapter = if queue_adapter?(name_or_adapter_or_class)
+          if queue_adapter?(name_or_adapter_or_class)
             name_or_adapter_or_class
           elsif queue_adapter_class?(name_or_adapter_or_class)
             ActiveSupport::Deprecation.warn "Passing an adapter class is deprecated " \
-            "and will be removed in Rails 5.1. Please pass an adapter name " \
-            "(.queue_adapter = :#{name_or_adapter_or_class.name.demodulize.remove('Adapter').underscore}) " \
-            "or an instance (.queue_adapter = #{name_or_adapter_or_class.name}.new) instead."
-            name_or_adapter_or_class.new
+              "and will be removed in Rails 5.1. Please pass an adapter name " \
+              "(.queue_adapter = :#{name_or_adapter_or_class.name.demodulize.remove('Adapter').underscore}) " \
+              "or an instance (.queue_adapter = #{name_or_adapter_or_class.name}.new) instead."
+              name_or_adapter_or_class.new
           else
             raise ArgumentError
           end
         end
       end
 
-      private
-
       QUEUE_ADAPTER_METHODS = [:enqueue, :enqueue_at].freeze
 
       def queue_adapter?(object)
diff --git a/activejob/lib/active_job/test_helper.rb b/activejob/lib/active_job/test_helper.rb
index 5e309c1dca..4efb4b72d2 100644
--- a/activejob/lib/active_job/test_helper.rb
+++ b/activejob/lib/active_job/test_helper.rb
@@ -1,3 +1,4 @@
+require 'active_support/core_ext/class/subclasses'
 require 'active_support/core_ext/hash/keys'
 
 module ActiveJob
@@ -7,8 +8,17 @@ module ActiveJob
 
     included do
       def before_setup
-        @old_queue_adapter = queue_adapter
-        ActiveJob::Base.queue_adapter = :test
+        test_adapter = ActiveJob::QueueAdapters::TestAdapter.new
+
+        @old_queue_adapters = (ActiveJob::Base.subclasses << ActiveJob::Base).select do |klass|
+          # only override explicitly set adapters, a quirk of `class_attribute`
+          klass.singleton_class.public_instance_methods(false).include?(:_queue_adapter)
+        end.map do |klass|
+          [klass, klass.queue_adapter].tap do
+            klass.queue_adapter = test_adapter
+          end
+        end
+
         clear_enqueued_jobs
         clear_performed_jobs
         super
@@ -16,7 +26,9 @@ module ActiveJob
 
       def after_teardown
         super
-        ActiveJob::Base.queue_adapter = @old_queue_adapter
+        @old_queue_adapters.each do |(klass, adapter)|
+          klass.queue_adapter = adapter
+        end
       end
 
       # Asserts that the number of enqueued jobs matches the given number.