Fix config.active_record.destroy_association_async_job configuration

`config.active_record.destroy_association_async_job` should allow applications
to specify the job that will be used to destroy associated records in the
background for `has_many` associations with the `dependent: :destroy_async`
option. That's being ignored, which means the default
`ActiveRecord::DestroyAssociationAsyncJob` always destroys records in the
background. This change stops ignoring the configuration.

Author: nholden

activejob/lib/active_job/railtie.rb

@@ -43,7 +43,7 @@ class Railtie < Rails::Railtie # :nodoc:
       end
 
       ActiveSupport.on_load(:active_record) do
-        self.destroy_association_async_job = ActiveRecord::DestroyAssociationAsyncJob
+        self.destroy_association_async_job ||= ActiveRecord::DestroyAssociationAsyncJob
       end
     end
 

activerecord/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   Fix `config.active_record.destroy_association_async_job` configuration
+
+    `config.active_record.destroy_association_async_job` should allow
+    applications to specify the job that will be used to destroy associated
+    records in the background for `has_many` associations with the
+    `dependent: :destroy_async` option. Previously, that was ignored, which
+    meant the default `ActiveRecord::DestroyAssociationAsyncJob` always
+    destroyed records in the background.
+
+    *Nick Holden*
+
 *   Fix quoting of `ActiveSupport::Duration` and `Rational` numbers in the MySQL adapter.
 
     *Kevin McPhillips*

railties/test/application/configuration_test.rb

@@ -2444,6 +2444,20 @@ class ::DummySerializer < ActiveJob::Serializers::ObjectSerializer; end
       assert_equal ActiveRecord::DestroyAssociationAsyncJob, ActiveRecord::Base.destroy_association_async_job
     end
 
+    test "ActiveRecord::Base.destroy_association_async_job can be configured via config.active_record.destroy_association_job" do
+      class ::DummyDestroyAssociationAsyncJob; end
+
+      app_file "config/environments/test.rb", <<-RUBY
+        Rails.application.configure do
+          config.active_record.destroy_association_async_job = DummyDestroyAssociationAsyncJob
+        end
+      RUBY
+
+      app "test"
+
+      assert_equal DummyDestroyAssociationAsyncJob, ActiveRecord::Base.destroy_association_async_job
+    end
+
     test "ActionView::Helpers::FormTagHelper.default_enforce_utf8 is false by default" do
       app "development"
       assert_equal false, ActionView::Helpers::FormTagHelper.default_enforce_utf8