Clear any existing payment and payment fees when adding a voucher

If a user come back to checkout step 2 from step 3, the order
will have payment and possibly payment fee existing. This can
interfere with voucher calculation, so we clear them.
The user can then select a payment method again if needed

app/controllers/voucher_adjustments_controller.rb

@@ -47,6 +47,10 @@ class VoucherAdjustmentsController < BaseController
       return false
     end
 
+    # Clear payments and payment_fee, to not affect voucher adjustment calculation
+    @order.all_adjustments.payment_fee.destroy_all
+    @order.payments.clear
+
     VoucherAdjustmentsService.new(@order).update
     @order.update_totals_and_states
 

spec/requests/voucher_adjustments_spec.rb

@@ -8,7 +8,7 @@ describe VoucherAdjustmentsController, type: :request do
   let(:distributor) { create(:distributor_enterprise, with_payment_and_shipping: true) }
   let(:order_cycle) { create(:order_cycle, distributors: [distributor]) }
   let(:exchange) { order_cycle.exchanges.outgoing.first }
-  let(:order) do
+  let!(:order) do
     create(
       :order_with_line_items,
       line_items_count: 1,
@@ -66,6 +66,29 @@ describe VoucherAdjustmentsController, type: :request do
         )
       end
     end
+
+    context "when the order has a payment and payment feed" do
+      let(:payment_method) { create(:payment_method, calculator: calculator) }
+      let(:calculator) do
+        ::Calculator::FlatPercentItemTotal.new(preferred_flat_percent: 10)
+      end
+
+      before do
+        create(:payment, order: order, payment_method: payment_method, amount: order.total)
+      end
+
+      it "removes existing payments" do
+        expect do
+          post "/voucher_adjustments", params: params
+        end.to change { order.reload.payments.count }.from(1).to(0)
+      end
+
+      it "removes existing payment fees" do
+        expect do
+          post "/voucher_adjustments", params: params
+        end.to change { order.reload.all_adjustments.payment_fee.count }.from(1).to(0)
+      end
+    end
   end
 
   describe "DELETE voucher_adjustments/:id" do