Use order total excluding discounts in voucher calculations

app/models/spree/adjustment.rb

@@ -67,6 +67,8 @@ module Spree
     scope :charge, -> { where('amount >= 0') }
     scope :credit, -> { where('amount < 0') }
     scope :return_authorization, -> { where(originator_type: "Spree::ReturnAuthorization") }
+    scope :voucher, -> { where(originator_type: "Voucher") }
+    scope :non_voucher, -> { where.not(originator_type: "Voucher") }
     scope :inclusive, -> { where(included: true) }
     scope :additional, -> { where(included: false) }
     scope :legacy_tax, -> { additional.tax.where(adjustable_type: "Spree::Order") }

app/models/spree/order.rb

@@ -171,6 +171,11 @@ module Spree
       line_items.inject(0.0) { |sum, li| sum + li.amount }
     end
 
+    # Order total without any applied discounts from vouchers
+    def pre_discount_total
+      item_total + all_adjustments.additional.eligible.non_voucher.sum(:amount)
+    end
+
     def currency
       self[:currency] || Spree::Config[:currency]
     end

app/models/voucher.rb

@@ -41,6 +41,6 @@ class Voucher < ApplicationRecord
   # We limit adjustment to the maximum amount needed to cover the order, ie if the voucher
   # covers more than the order.total we only need to create an adjustment covering the order.total
   def compute_amount(order)
-    -amount.clamp(0, order.total)
+    -amount.clamp(0, order.pre_discount_total)
   end
 end

spec/services/voucher_adjustments_service_spec.rb

@@ -14,9 +14,7 @@ describe VoucherAdjustmentsService do
 
       it 'updates the adjustment amount to -order.total' do
         voucher.create_adjustment(voucher.code, order)
-
-        order.total = 6
-        order.save!
+        order.update_columns(item_total: 6)
 
         VoucherAdjustmentsService.calculate(order)
 

spec/system/consumer/split_checkout_spec.rb

@@ -1114,11 +1114,8 @@ describe "As a consumer, I want to checkout my order" do
         let(:voucher) { create(:voucher, code: 'some_code', enterprise: distributor, amount: 6) }
 
         before do
-          # Add voucher to the order
           voucher.create_adjustment(voucher.code, order)
-
-          # Update order so voucher adjustment is properly taken into account
-          order.update_order!
+          order.update_totals
           VoucherAdjustmentsService.calculate(order)
 
           visit checkout_step_path(:summary)