Add ability to set default order of PaperTrail versions

Closes #3095

lib/rails_admin/extensions/paper_trail/auditing_adapter.rb

@@ -100,9 +100,13 @@ def initialize(controller, user_class_name = nil, version_class_name = nil, &blo
           raise E_VERSION_MODEL_NOT_SET
         end
 
+        register_instance_option :sort_by do
+          {id: :desc}
+        end
+
         def latest(count = 100)
           version_class.
-            order(id: :desc).includes(:item).limit(count).
+            order(sort_by).includes(:item).limit(count).
             collect { |version| VersionProxy.new(version, user_class) }
         end
 
@@ -130,18 +134,18 @@ def listing_for_object(model, object, query, sort, sort_reverse, all, page, per_
 
         # - model - a RailsAdmin::AbstractModel
         def listing_for_model_or_object(model, object, query, sort, sort_reverse, all, page, per_page)
-          if sort.present?
-            sort = COLUMN_MAPPING[sort.to_sym]
-          else
-            sort = :created_at
-            sort_reverse = 'true'
-          end
+          sort =
+            if sort.present?
+              {COLUMN_MAPPING[sort.to_sym] => sort_reverse ? :desc : :asc}
+            else
+              sort_by
+            end
 
           current_page = page.presence || '1'
 
           versions = object.nil? ? versions_for_model(model) : object.public_send(model.model.versions_association_name)
           versions = versions.where('event LIKE ?', "%#{query}%") if query.present?
-          versions = versions.order(sort_reverse == 'true' ? "#{sort} DESC" : sort)
+          versions = versions.order(sort)
           versions = all ? versions : versions.send(Kaminari.config.page_method_name, current_page).per(per_page)
           paginated_proxies = Kaminari.paginate_array([], total_count: versions.try(:total_count) || versions.count)
           paginated_proxies = paginated_proxies.send(

spec/rails_admin/extentions/paper_trail/auditing_adapter_spec.rb

@@ -16,9 +16,26 @@
       adapter = described_class.new(controller) do
         user_class User::Confirmed
         version_class Trail
+        sort_by(created_at: :asc)
       end
       expect(adapter.user_class).to eq User::Confirmed
       expect(adapter.version_class).to eq Trail
+      expect(adapter.sort_by).to eq({created_at: :asc})
+    end
+  end
+
+  describe '#listing_for_model' do
+    subject { RailsAdmin::Extensions::PaperTrail::AuditingAdapter.new(nil) }
+    let(:model) { RailsAdmin::AbstractModel.new(PaperTrailTest) }
+
+    it 'uses the given sort order' do
+      expect_any_instance_of(ActiveRecord::Relation).to receive(:order).with(whodunnit: :asc).and_call_original
+      subject.listing_for_model model, nil, :username, false, true, nil, 20
+    end
+
+    it 'uses the default order when sort is not given' do
+      expect_any_instance_of(ActiveRecord::Relation).to receive(:order).with(id: :desc).and_call_original
+      subject.listing_for_model model, nil, false, false, true, nil, 20
     end
   end
 end