Add Spree::Promotion#discounted_orders

core/app/models/spree/promotion.rb

@@ -68,6 +68,14 @@ def self.with_coupon_code(val)
       ).first
     end
 
+    def discounted_orders
+      Spree::Order.where.not(spree_line_item_discounts: { id: nil }).
+        where(spree_line_item_discounts: { promotion_action_id: actions.map(&:id) }).or(
+          Spree::Order.where.not(spree_shipment_discounts: { id: nil }).
+            where(spree_shipment_discounts: { promotion_action_id: actions.map(&:id) })
+      ).left_outer_joins(line_items: :discounts, shipments: :discounts).distinct
+    end
+
     def as_json(options = {})
       options[:except] ||= :code
       super

core/spec/models/spree/promotion_spec.rb

@@ -1144,4 +1144,44 @@
       expect(order.adjustment_total).to eq(-10)
     end
   end
+
+  describe "#discounted_orders" do
+    let(:promotion) { create(:promotion, :with_action) }
+    let(:other_promotion) { create(:promotion, :with_action) }
+    let(:other_action) { other_promotion.actions.first }
+    let(:action) { promotion.actions.first }
+
+    let!(:order_with_line_item_discount) do
+      create(:order_with_line_items).tap do |order|
+        order.line_items.first.discounts << build(:line_item_discount, line_item: nil, promotion_action: action)
+      end
+    end
+
+    let!(:order_with_shipment_discount) do
+      create(:order_with_line_items).tap do |order|
+        order.shipments.first.discounts << build(:shipment_discount, shipment: nil, promotion_action: action)
+      end
+    end
+
+    let!(:order_with_line_item_and_shipment_discount) do
+      create(:order_with_line_items).tap do |order|
+        order.shipments.first.discounts << build(:shipment_discount, shipment: nil, promotion_action: action)
+        order.line_items.first.discounts << build(:line_item_discount, line_item: nil, promotion_action: action)
+      end
+    end
+
+    let!(:order_without_discount) { create(:order_with_line_items) }
+
+    let!(:order_with_other_discount) do
+      create(:order_with_line_items).tap do |order|
+        order.shipments.first.discounts << build(:shipment_discount, shipment: nil, promotion_action: other_action)
+      end
+    end
+
+    subject { promotion.discounted_orders }
+
+    it { is_expected.to be_a(ActiveRecord::Relation) }
+
+    it { is_expected.to match_array([order_with_line_item_and_shipment_discount, order_with_shipment_discount, order_with_line_item_discount]) }
+  end
 end