Enable/Disable store credit at checkout step

Author: DanielePalombo

core/app/models/spree/order.rb

@@ -676,8 +676,6 @@ def add_store_credit_payments
 
       remaining_total = outstanding_balance - authorized_total
 
-      matching_store_credits = user.store_credits.where(currency: currency)
-
       if matching_store_credits.any?
         payment_method = Spree::PaymentMethod::StoreCredit.first
 
@@ -824,6 +822,20 @@ def validate_payments_attributes(attributes)
 
     private
 
+    def matching_store_credits
+      @matching_store_credits ||= if use_store_credits?
+                                    user.store_credits.where(currency: currency)
+                                  else
+                                    []
+                                  end
+    end
+
+    def use_store_credits?
+      return Spree::Config[:default_use_store_credits] if use_store_credits.nil?
+
+      super
+    end
+
     def process_payments_before_complete
       return if !payment_required?
 

core/db/migrate/20200525083006_add_use_store_credits_to_spree_orders.rb

@@ -0,0 +1,5 @@
+class AddUseStoreCreditsToSpreeOrders < ActiveRecord::Migration[5.2]
+  def change
+    add_column :spree_orders, :use_store_credits, :boolean, default: nil
+  end
+end

core/lib/spree/app_configuration.rb

@@ -56,6 +56,10 @@ class AppConfiguration < Preferences::Configuration
     #   @return [Boolean] When false, customers must create an account to complete an order (default: +true+)
     preference :allow_guest_checkout, :boolean, default: true
 
+    # @!attribute [rw] default_use_store_credits
+    #   @return [Boolean] When true, user store credits will applied for default (default: +true+)
+    preference :default_use_store_credits, :boolean, default: true
+
     # @!attribute [rw] guest_token_cookie_options
     #   @return [Hash] Add additional guest_token cookie options here (ie. domain or path)
     preference :guest_token_cookie_options, :hash, default: {}

core/spec/models/spree/order_spec.rb

@@ -1297,10 +1297,26 @@ def generate
         end
 
         context "there is a credit card payment" do
+          subject(:add_store_credit_payments!) { order.add_store_credit_payments }
+
+          let!(:cc_payment) { create(:payment, order: order) }
+
           it "invalidates the credit card payment" do
-            cc_payment = create(:payment, order: order)
             expect { subject }.to change { cc_payment.reload.state }.to 'invalid'
           end
+
+          context "when the order doesn't use store credits" do
+            let(:order) do
+              create(:order_with_totals,
+                     use_store_credits: false,
+                     user: store_credit.user,
+                     line_items_price: order_total).tap(&:recalculate)
+            end
+
+            it "doesn't invalidates the credit card payment" do
+              expect { add_store_credit_payments! }.not_to(change { cc_payment.reload.state })
+            end
+          end
         end
       end