Add spec coverage, refactor, avoid double-render errors

👍

app/controllers/checkout_controller.rb

@@ -25,7 +25,7 @@ class CheckoutController < Spree::StoreController
 
   before_action :ensure_order_not_completed
   before_action :ensure_checkout_allowed
-  before_action :ensure_sufficient_stock_lines
+  before_action :handle_insufficient_stock
 
   before_action :associate_user
   before_action :check_authorization

app/controllers/concerns/order_stock_check.rb

@@ -3,10 +3,16 @@
 module OrderStockCheck
   extend ActiveSupport::Concern
 
-  def ensure_sufficient_stock_lines
-    return true if @order.insufficient_stock_lines.blank?
+  def handle_insufficient_stock
+    return if sufficient_stock?
 
     flash[:error] = Spree.t(:inventory_error_flash_for_insufficient_quantity)
     redirect_to main_app.cart_path
   end
+
+  private
+
+  def sufficient_stock?
+    @sufficient_stock ||= @order.insufficient_stock_lines.blank?
+  end
 end

app/controllers/spree/paypal_controller_decorator.rb

@@ -58,9 +58,10 @@ Spree::PaypalController.class_eval do
 
   def confirm
     @order = current_order || raise(ActiveRecord::RecordNotFound)
+
     # At this point the user has come back from the Paypal form, and we get one
     # last chance to interact with the payment process before the money moves...
-    return unless ensure_sufficient_stock_lines
+    return handle_insufficient_stock unless sufficient_stock?
 
     @order.payments.create!({
       source: Spree::PaypalExpressCheckout.create({

spec/controllers/spree/paypal_controller_spec.rb

@@ -27,6 +27,20 @@ module Spree
         spree_post :confirm, payment_method_id: payment_method.id
         expect(session[:access_token]).to eq(controller.current_order.token)
       end
+
+      context "if the stock ran out whilst the payment was being placed" do
+        before do
+          allow(controller.current_order).to receive(:insufficient_stock_lines).and_return(true)
+        end
+
+        it "redirects to the cart with out of stock error" do
+          expect(spree_post(:confirm, payment_method_id: payment_method.id)).
+            to redirect_to cart_path
+
+          # And does not complete processing of the payment
+          expect(controller.current_order.reload.payments.count).to eq 0
+        end
+      end
     end
 
     describe '#expire_current_order' do