reduce n+1 queries and fix specs

core/app/models/spree/product.rb

@@ -190,9 +190,10 @@ def self.like_any(fields, values)
     # values should not be displayed to frontend users. Otherwise it breaks the
     # idea of having variants
     def variants_and_option_values(current_currency = nil)
-      variants.includes(:option_values).active(current_currency).select do |variant|
-        variant.option_values.any?
-      end
+      variants.includes(:option_values, :prices, :stock_items_with_active_location).
+        active(current_currency).select do |variant|
+          variant.option_values.any?
+        end
     end
 
     def empty_option_values?

core/app/models/spree/stock/quantifier.rb

@@ -5,12 +5,12 @@ class Quantifier
 
       def initialize(variant)
         @variant = variant
-        @stock_items = @variant.stock_items.with_active_stock_location
+        @stock_items = @variant.stock_items_with_active_location
       end
 
       def total_on_hand
         if variant.should_track_inventory?
-          stock_items.sum(:count_on_hand)
+          stock_items.inject(0) { |result, stock_item| result + stock_item.count_on_hand }
         else
           Float::INFINITY
         end

core/app/models/spree/stock_item.rb

@@ -4,6 +4,9 @@ class StockItem < Spree::Base
 
     with_options inverse_of: :stock_items do
       belongs_to :stock_location, class_name: 'Spree::StockLocation'
+      belongs_to :active_stock_location, -> { where(active: true) },
+                                         class_name: 'Spree::StockLocation',
+                                         foreign_key: :stock_location_id
       belongs_to :variant, class_name: 'Spree::Variant', counter_cache: true
     end
     has_many :stock_movements, inverse_of: :stock_item
@@ -24,7 +27,7 @@ class StockItem < Spree::Base
 
     self.whitelisted_ransackable_attributes = ['count_on_hand', 'stock_location_id']
 
-    scope :with_active_stock_location, -> { joins(:stock_location).merge(Spree::StockLocation.active) }
+    scope :with_active_stock_location, -> { joins(:active_stock_location) }
 
     def backordered_inventory_units
       Spree::InventoryUnit.backordered_for_stock_item(self)

core/app/models/spree/variant.rb

@@ -15,6 +15,9 @@ class Variant < Spree::Base
     with_options inverse_of: :variant do
       has_many :inventory_units
       has_many :stock_items, dependent: :destroy
+      has_many :stock_items_with_active_location, -> { with_active_stock_location },
+                                                  class_name: "Spree::StockItem",
+                                                  dependent: :destroy
     end
 
     has_many :line_items, dependent: :restrict_with_error

core/spec/models/spree/line_item_spec.rb

@@ -243,6 +243,7 @@
 
       it "doesnt allow to increase item quantity" do
         line_item = order.line_items.first
+        line_item.reload
         line_item.quantity += 2
         line_item.target_shipment = order.shipments.first
 
@@ -270,6 +271,7 @@
 
       it "doesnt allow to increase quantity over stock availability" do
         line_item = order.line_items.first
+        line_item.reload
         line_item.quantity += 3
         line_item.target_shipment = order.shipments.first
 

core/spec/models/spree/stock_item_spec.rb

@@ -5,6 +5,15 @@
 
   subject { stock_location.stock_items.order(:id).first }
 
+  describe "associations" do
+    it do
+      is_expected.to belong_to(:active_stock_location).
+        conditions(active: true).
+        class_name("Spree::StockLocation").
+        with_foreign_key(:stock_location_id)
+    end
+  end
+
   it 'maintains the count on hand for a variant' do
     expect(subject.count_on_hand).to eq 10
   end

core/spec/models/spree/variant_spec.rb

@@ -8,6 +8,15 @@
 
   it_behaves_like 'default_price'
 
+  describe 'associations' do
+    it do
+      is_expected.to have_many(:stock_items_with_active_location).
+        conditions(:with_active_stock_location).
+        class_name("Spree::StockItem").
+        dependent(:destroy)
+    end
+  end
+
   describe 'validations' do
     it { expect(master_variant).to_not validate_presence_of(:option_values) }
     it { expect(variant).to validate_presence_of(:option_values) }
@@ -58,6 +67,7 @@
 
       context 'when a variant is created' do
         let!(:new_variant) { create(:variant, product: product) }
+        before { product.reload }
 
         it { expect(product.master).to_not be_in_stock }
       end

frontend/app/controllers/spree/products_controller.rb

@@ -40,7 +40,7 @@ def load_product
         else
           @products = Product.active(current_currency)
         end
-        @product = @products.includes(:variants_including_master).friendly.find(params[:id])
+        @product = @products.includes(variant_images: :viewable).friendly.find(params[:id])
       end
 
       def load_taxon