Extract #process_payment_completion!

app/controllers/concerns/order_completion.rb

@@ -50,6 +50,21 @@ module OrderCompletion
     redirect_to main_app.shop_path
   end
 
+  def process_payment_completion!
+    return processing_failed unless @order.process_payments!
+
+    if OrderWorkflow.new(@order).next && @order.complete?
+      processing_succeeded
+      redirect_to order_completion_route
+    else
+      processing_failed
+      redirect_to order_failed_route
+    end
+  rescue Spree::Core::GatewayError => e
+    gateway_error(e)
+    processing_failed
+  end
+
   def processing_succeeded
     Checkout::PostCheckoutActions.new(@order).success(params, spree_current_user)
     order_completion_reset(@order)

app/controllers/payment_gateways/paypal_controller.rb

@@ -49,16 +49,8 @@ module PaymentGateways
         amount: @order.total,
         payment_method: payment_method
       )
-      @order.process_payments!
-      @order.next
 
-      if @order.complete?
-        processing_succeeded
-        redirect_to order_completion_route
-      else
-        processing_failed
-        redirect_to order_failed_route
-      end
+      process_payment_completion!
     end
 
     def cancel

app/controllers/payment_gateways/stripe_controller.rb

@@ -9,7 +9,7 @@ class StripeController < BaseController
   def confirm
     return processing_failed unless valid_payment_intent?
 
-    process_payment_completion
+    process_payment_completion!
   end
 
   private
@@ -34,21 +34,6 @@ class StripeController < BaseController
     end
   end
 
-  def process_payment_completion
-    return processing_failed unless @order.process_payments!
-
-    if OrderWorkflow.new(@order).next && @order.complete?
-      processing_succeeded
-      redirect_to order_completion_route
-    else
-      processing_failed
-      redirect_to order_failed_route
-    end
-  rescue Spree::Core::GatewayError => e
-    gateway_error(e)
-    processing_failed
-  end
-
   def cancel_incomplete_payments
     # The checkout could not complete due to stock running out. We void any pending (incomplete)
     # Stripe payments here as the order will need to be changed and resubmitted (or abandoned).