From 0e711832fdff9f91ac2e70b9c1038d60cb1961e8 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:13:21 +0800
Subject: [PATCH 01/19] Bring Spree::StockItem code from spree_core into the
 app

---
 app/models/spree/stock_item.rb       | 52 +++++++++++++++++++
 spec/models/spree/stock_item_spec.rb | 74 ++++++++++++++++++++++++++++
 2 files changed, 126 insertions(+)
 create mode 100644 app/models/spree/stock_item.rb
 create mode 100644 spec/models/spree/stock_item_spec.rb

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
new file mode 100644
index 0000000000..9dc322b447
--- /dev/null
+++ b/app/models/spree/stock_item.rb
@@ -0,0 +1,52 @@
+module Spree
+  class StockItem < ActiveRecord::Base
+    belongs_to :stock_location, class_name: 'Spree::StockLocation'
+    belongs_to :variant, class_name: 'Spree::Variant'
+    has_many :stock_movements, dependent: :destroy
+
+    validates_presence_of :stock_location, :variant
+    validates_uniqueness_of :variant_id, scope: :stock_location_id
+
+    attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
+
+    delegate :weight, to: :variant
+
+    def backordered_inventory_units
+      Spree::InventoryUnit.backordered_for_stock_item(self)
+    end
+
+    def variant_name
+      variant.name
+    end
+
+    def adjust_count_on_hand(value)
+      self.with_lock do
+        self.count_on_hand = self.count_on_hand + value
+        process_backorders if in_stock?
+
+        self.save!
+      end
+    end
+
+    def in_stock?
+      self.count_on_hand > 0
+    end
+
+    # Tells whether it's available to be included in a shipment
+    def available?
+      self.in_stock? || self.backorderable?
+    end
+
+    private
+      def count_on_hand=(value)
+        write_attribute(:count_on_hand, value)
+      end
+
+      def process_backorders
+        backordered_inventory_units.each do |unit|
+          return unless in_stock?
+          unit.fill_backorder
+        end
+      end
+  end
+end
diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
new file mode 100644
index 0000000000..da10d44efa
--- /dev/null
+++ b/spec/models/spree/stock_item_spec.rb
@@ -0,0 +1,74 @@
+require 'spec_helper'
+
+describe Spree::StockItem do
+  let(:stock_location) { create(:stock_location_with_items) }
+
+  subject { stock_location.stock_items.order(:id).first }
+
+  it 'maintains the count on hand for a variant' do
+    subject.count_on_hand.should eq 10
+  end
+
+  it "can return the stock item's variant's name" do
+    subject.variant_name.should == subject.variant.name
+  end
+
+  context "available to be included in shipment" do
+    context "has stock" do
+      it { subject.should be_available }
+    end
+
+    context "backorderable" do
+      before { subject.backorderable = true }
+      it { subject.should be_available }
+    end
+
+    context "no stock and not backorderable" do
+      before do
+        subject.backorderable = false
+        subject.stub(count_on_hand: 0)
+      end
+
+      it { subject.should_not be_available }
+    end
+  end
+
+  context "adjust count_on_hand" do
+    let!(:current_on_hand) { subject.count_on_hand }
+
+    it 'is updated pessimistically' do
+      copy = Spree::StockItem.find(subject.id)
+
+      subject.adjust_count_on_hand(5)
+      subject.count_on_hand.should eq(current_on_hand + 5)
+
+      copy.count_on_hand.should eq(current_on_hand)
+      copy.adjust_count_on_hand(5)
+      copy.count_on_hand.should eq(current_on_hand + 10)
+    end
+
+    context "item out of stock (by two items)" do
+      let(:inventory_unit) { double('InventoryUnit') }
+      let(:inventory_unit_2) { double('InventoryUnit2') }
+
+      before { subject.adjust_count_on_hand(- (current_on_hand + 2)) }
+
+      it "doesn't process backorders" do
+        subject.should_not_receive(:backordered_inventory_units)
+        subject.adjust_count_on_hand(1)
+      end
+
+      context "adds new items" do
+        before { subject.stub(:backordered_inventory_units => [inventory_unit, inventory_unit_2]) }
+
+        it "fills existing backorders" do
+          inventory_unit.should_receive(:fill_backorder)
+          inventory_unit_2.should_receive(:fill_backorder)
+
+          subject.adjust_count_on_hand(3)
+          subject.count_on_hand.should == 1
+        end
+      end
+    end
+  end
+end

From 84d973d383d816b2760a4c0c4bf926875a341cae Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:19:24 +0800
Subject: [PATCH 02/19] Specify RSpec.describe in StockItem spec file

---
 spec/models/spree/stock_item_spec.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index da10d44efa..2e6b757a71 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -1,6 +1,6 @@
 require 'spec_helper'
 
-describe Spree::StockItem do
+RSpec.describe Spree::StockItem do
   let(:stock_location) { create(:stock_location_with_items) }
 
   subject { stock_location.stock_items.order(:id).first }

From b78311870065f63246831d30dbf1ad91ea9c292d Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:40:13 +0800
Subject: [PATCH 03/19] Auto-correct violationso of Rubocop Style/RedundantSelf

---
 app/models/spree/stock_item.rb | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 9dc322b447..70bb741e8d 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -20,21 +20,21 @@ module Spree
     end
 
     def adjust_count_on_hand(value)
-      self.with_lock do
-        self.count_on_hand = self.count_on_hand + value
+      with_lock do
+        self.count_on_hand = count_on_hand + value
         process_backorders if in_stock?
 
-        self.save!
+        save!
       end
     end
 
     def in_stock?
-      self.count_on_hand > 0
+      count_on_hand > 0
     end
 
     # Tells whether it's available to be included in a shipment
     def available?
-      self.in_stock? || self.backorderable?
+      in_stock? || backorderable?
     end
 
     private

From 0fd66f9a558caccfa639a864c636261bf17a0962 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:44:07 +0800
Subject: [PATCH 04/19] Auto-correct violationso of Rubocop Style/*

---
 app/models/spree/stock_item.rb       | 1 +
 spec/models/spree/stock_item_spec.rb | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 70bb741e8d..d1c9faa983 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Spree
   class StockItem < ActiveRecord::Base
     belongs_to :stock_location, class_name: 'Spree::StockLocation'
diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index 2e6b757a71..f58a0bd09c 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'spec_helper'
 
 RSpec.describe Spree::StockItem do
@@ -59,7 +60,7 @@ RSpec.describe Spree::StockItem do
       end
 
       context "adds new items" do
-        before { subject.stub(:backordered_inventory_units => [inventory_unit, inventory_unit_2]) }
+        before { subject.stub(backordered_inventory_units: [inventory_unit, inventory_unit_2]) }
 
         it "fills existing backorders" do
           inventory_unit.should_receive(:fill_backorder)

From d1725014c4495481c83e9dd0b88febbd1b150e4e Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:44:23 +0800
Subject: [PATCH 05/19] Auto-correct violationso of Rubocop Layout/*

---
 app/models/spree/stock_item.rb       | 19 +++++++++++--------
 spec/models/spree/stock_item_spec.rb |  1 +
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index d1c9faa983..29ec2401fa 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 module Spree
   class StockItem < ActiveRecord::Base
     belongs_to :stock_location, class_name: 'Spree::StockLocation'
@@ -39,15 +40,17 @@ module Spree
     end
 
     private
-      def count_on_hand=(value)
-        write_attribute(:count_on_hand, value)
-      end
 
-      def process_backorders
-        backordered_inventory_units.each do |unit|
-          return unless in_stock?
-          unit.fill_backorder
-        end
+    def count_on_hand=(value)
+      write_attribute(:count_on_hand, value)
+    end
+
+    def process_backorders
+      backordered_inventory_units.each do |unit|
+        return unless in_stock?
+
+        unit.fill_backorder
       end
+    end
   end
 end
diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index f58a0bd09c..c59416371d 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'spec_helper'
 
 RSpec.describe Spree::StockItem do

From 22c0693bebdf65346f11ab914db87b35a1166fe5 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:45:52 +0800
Subject: [PATCH 06/19] Address violation of Rubocop Style/NumericPredicate

---
 app/models/spree/stock_item.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 29ec2401fa..5c9f390567 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -31,7 +31,7 @@ module Spree
     end
 
     def in_stock?
-      count_on_hand > 0
+      count_on_hand.positive?
     end
 
     # Tells whether it's available to be included in a shipment

From 1e8543dfe7a9a1c420fc0011a1012a064d8daf97 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:50:57 +0800
Subject: [PATCH 07/19] Address violation of Rubocop Rails/ReadWriteAttribute

---
 app/models/spree/stock_item.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 5c9f390567..47bbf14fbd 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -42,7 +42,7 @@ module Spree
     private
 
     def count_on_hand=(value)
-      write_attribute(:count_on_hand, value)
+      self[:count_on_hand] = value
     end
 
     def process_backorders

From 2acf61fd0f08ab8424c3d8422c469d82cc1dc226 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:54:50 +0800
Subject: [PATCH 08/19] Address violation of Rubocop Rails/Delegate

---
 app/models/spree/stock_item.rb | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 47bbf14fbd..44aa72f422 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -17,9 +17,7 @@ module Spree
       Spree::InventoryUnit.backordered_for_stock_item(self)
     end
 
-    def variant_name
-      variant.name
-    end
+    delegate :name, to: :variant, prefix: true
 
     def adjust_count_on_hand(value)
       with_lock do

From bc530b92b540bf2639872f8832633230c35e85eb Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 04:55:42 +0800
Subject: [PATCH 09/19] Address violation of Rubocop Rails/Validation:

---
 app/models/spree/stock_item.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 44aa72f422..47c311b205 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -6,8 +6,8 @@ module Spree
     belongs_to :variant, class_name: 'Spree::Variant'
     has_many :stock_movements, dependent: :destroy
 
-    validates_presence_of :stock_location, :variant
-    validates_uniqueness_of :variant_id, scope: :stock_location_id
+    validates :stock_location, :variant, presence: true
+    validates :variant_id, uniqueness: { scope: :stock_location_id }
 
     attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
 

From 0a1cb71ee4f8b64c52ade2a98d73563e2f524460 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 05:00:52 +0800
Subject: [PATCH 10/19] Ignore Rails/UniqueValidationWithoutIndex for unique
 index of StockItem#stock_location

---
 app/models/spree/stock_item.rb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 47c311b205..9eca73d0c8 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -7,7 +7,9 @@ module Spree
     has_many :stock_movements, dependent: :destroy
 
     validates :stock_location, :variant, presence: true
+    # rubocop:disable Rails/UniqueValidationWithoutIndex
     validates :variant_id, uniqueness: { scope: :stock_location_id }
+    # rubocop:enable Rails/UniqueValidationWithoutIndex
 
     attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
 

From fb20f220c04f83f938fee31f7023d9c8e01b88e7 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 05:16:58 +0800
Subject: [PATCH 11/19] Use break instead of return in
 StockItem#process_backorders

We are not using the return value of this method anywhere.
---
 app/models/spree/stock_item.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index 9eca73d0c8..b3e14969eb 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -47,7 +47,7 @@ module Spree
 
     def process_backorders
       backordered_inventory_units.each do |unit|
-        return unless in_stock?
+        break unless in_stock?
 
         unit.fill_backorder
       end

From 13ecf0ec73ba49782fe1a92e1c186196c14598fb Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 15:20:20 +0800
Subject: [PATCH 12/19] Update specs for StockItem with transpec

---
 spec/models/spree/stock_item_spec.rb | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index c59416371d..ce5c7fafd0 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -8,30 +8,30 @@ RSpec.describe Spree::StockItem do
   subject { stock_location.stock_items.order(:id).first }
 
   it 'maintains the count on hand for a variant' do
-    subject.count_on_hand.should eq 10
+    expect(subject.count_on_hand).to eq 10
   end
 
   it "can return the stock item's variant's name" do
-    subject.variant_name.should == subject.variant.name
+    expect(subject.variant_name).to eq(subject.variant.name)
   end
 
   context "available to be included in shipment" do
     context "has stock" do
-      it { subject.should be_available }
+      it { expect(subject).to be_available }
     end
 
     context "backorderable" do
       before { subject.backorderable = true }
-      it { subject.should be_available }
+      it { expect(subject).to be_available }
     end
 
     context "no stock and not backorderable" do
       before do
         subject.backorderable = false
-        subject.stub(count_on_hand: 0)
+        allow(subject).to receive_messages(count_on_hand: 0)
       end
 
-      it { subject.should_not be_available }
+      it { expect(subject).not_to be_available }
     end
   end
 
@@ -42,11 +42,11 @@ RSpec.describe Spree::StockItem do
       copy = Spree::StockItem.find(subject.id)
 
       subject.adjust_count_on_hand(5)
-      subject.count_on_hand.should eq(current_on_hand + 5)
+      expect(subject.count_on_hand).to eq(current_on_hand + 5)
 
-      copy.count_on_hand.should eq(current_on_hand)
+      expect(copy.count_on_hand).to eq(current_on_hand)
       copy.adjust_count_on_hand(5)
-      copy.count_on_hand.should eq(current_on_hand + 10)
+      expect(copy.count_on_hand).to eq(current_on_hand + 10)
     end
 
     context "item out of stock (by two items)" do
@@ -56,19 +56,19 @@ RSpec.describe Spree::StockItem do
       before { subject.adjust_count_on_hand(- (current_on_hand + 2)) }
 
       it "doesn't process backorders" do
-        subject.should_not_receive(:backordered_inventory_units)
+        expect(subject).not_to receive(:backordered_inventory_units)
         subject.adjust_count_on_hand(1)
       end
 
       context "adds new items" do
-        before { subject.stub(backordered_inventory_units: [inventory_unit, inventory_unit_2]) }
+        before { allow(subject).to receive_messages(backordered_inventory_units: [inventory_unit, inventory_unit_2]) }
 
         it "fills existing backorders" do
-          inventory_unit.should_receive(:fill_backorder)
-          inventory_unit_2.should_receive(:fill_backorder)
+          expect(inventory_unit).to receive(:fill_backorder)
+          expect(inventory_unit_2).to receive(:fill_backorder)
 
           subject.adjust_count_on_hand(3)
-          subject.count_on_hand.should == 1
+          expect(subject.count_on_hand).to eq(1)
         end
       end
     end

From 774b3720d5853a408de6b890add2df54981bec71 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Thu, 14 May 2020 15:23:31 +0800
Subject: [PATCH 13/19] Update stock item count on hand in Spree core specs

---
 spec/models/spree/stock_item_spec.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index ce5c7fafd0..679af05f90 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -8,7 +8,7 @@ RSpec.describe Spree::StockItem do
   subject { stock_location.stock_items.order(:id).first }
 
   it 'maintains the count on hand for a variant' do
-    expect(subject.count_on_hand).to eq 10
+    expect(subject.count_on_hand).to eq 15
   end
 
   it "can return the stock item's variant's name" do

From e53913756c17f90d3405af8258c15c8a66fba028 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Tue, 12 May 2020 15:09:53 +0800
Subject: [PATCH 14/19] Add lock_version to Spree::StockItem

---
 db/migrate/20200512070717_add_lock_version_to_stock_items.rb | 5 +++++
 db/schema.rb                                                 | 1 +
 2 files changed, 6 insertions(+)
 create mode 100644 db/migrate/20200512070717_add_lock_version_to_stock_items.rb

diff --git a/db/migrate/20200512070717_add_lock_version_to_stock_items.rb b/db/migrate/20200512070717_add_lock_version_to_stock_items.rb
new file mode 100644
index 0000000000..416a43f62e
--- /dev/null
+++ b/db/migrate/20200512070717_add_lock_version_to_stock_items.rb
@@ -0,0 +1,5 @@
+class AddLockVersionToStockItems < ActiveRecord::Migration
+  def change
+    add_column :spree_stock_items, :lock_version, :integer, default: 0
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index d166fdfd3c..d153eec8ef 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -899,6 +899,7 @@ ActiveRecord::Schema.define(version: 20200623140437) do
     t.datetime "updated_at"
     t.boolean  "backorderable",     default: false
     t.datetime "deleted_at"
+    t.integer  "lock_version",      default: 0
   end
 
   add_index "spree_stock_items", ["stock_location_id", "variant_id"], name: "stock_item_by_loc_and_var_id", using: :btree

From 4694f1b21a67467738e83859aa2ed537b4850dac Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Tue, 12 May 2020 15:28:26 +0800
Subject: [PATCH 15/19] Require count on hand in non backorderable StockItem to
 be positive or zero

Fix setting of count on hand in line item specs
---
 app/models/spree/stock_item.rb       |  1 +
 spec/models/spree/line_item_spec.rb  |  4 ++--
 spec/models/spree/stock_item_spec.rb | 32 +++++++++++++++++++++++++++-
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index b3e14969eb..f71df2b942 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -10,6 +10,7 @@ module Spree
     # rubocop:disable Rails/UniqueValidationWithoutIndex
     validates :variant_id, uniqueness: { scope: :stock_location_id }
     # rubocop:enable Rails/UniqueValidationWithoutIndex
+    validates :count_on_hand, numericality: { greater_than_or_equal_to: 0, unless: :backorderable? }
 
     attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
 
diff --git a/spec/models/spree/line_item_spec.rb b/spec/models/spree/line_item_spec.rb
index ca4a5353d9..ff00240aaf 100644
--- a/spec/models/spree/line_item_spec.rb
+++ b/spec/models/spree/line_item_spec.rb
@@ -97,7 +97,7 @@ module Spree
       end
 
       it "caps at zero when stock is negative" do
-        v.update! on_hand: -2
+        v.__send__(:stock_item).update_column(:count_on_hand, -2)
         li.cap_quantity_at_stock!
         expect(li.reload.quantity).to eq 0
       end
@@ -123,7 +123,7 @@ module Spree
           before { vo.update(count_on_hand: -3) }
 
           it "caps at zero" do
-            v.update(on_hand: -2)
+            v.__send__(:stock_item).update_column(:count_on_hand, -2)
             li.cap_quantity_at_stock!
             expect(li.reload.quantity).to eq 0
           end
diff --git a/spec/models/spree/stock_item_spec.rb b/spec/models/spree/stock_item_spec.rb
index 679af05f90..9c9b233986 100644
--- a/spec/models/spree/stock_item_spec.rb
+++ b/spec/models/spree/stock_item_spec.rb
@@ -7,6 +7,33 @@ RSpec.describe Spree::StockItem do
 
   subject { stock_location.stock_items.order(:id).first }
 
+  describe "validation" do
+    let(:stock_item) { stock_location.stock_items.first }
+
+    it "requires count_on_hand to be positive if not backorderable" do
+      stock_item.backorderable = false
+
+      stock_item.__send__(:count_on_hand=, 1)
+      expect(stock_item.valid?).to eq(true)
+
+      stock_item.__send__(:count_on_hand=, 0)
+      expect(stock_item.valid?).to eq(true)
+
+      stock_item.__send__(:count_on_hand=, -1)
+      expect(stock_item.valid?).to eq(false)
+    end
+
+    it "allows count_on_hand to be negative if backorderable" do
+      stock_item.backorderable = true
+
+      stock_item.__send__(:count_on_hand=, 1)
+      expect(stock_item.valid?).to eq(true)
+
+      stock_item.__send__(:count_on_hand=, -1)
+      expect(stock_item.valid?).to eq(true)
+    end
+  end
+
   it 'maintains the count on hand for a variant' do
     expect(subject.count_on_hand).to eq 15
   end
@@ -53,7 +80,10 @@ RSpec.describe Spree::StockItem do
       let(:inventory_unit) { double('InventoryUnit') }
       let(:inventory_unit_2) { double('InventoryUnit2') }
 
-      before { subject.adjust_count_on_hand(- (current_on_hand + 2)) }
+      before do
+        allow(subject).to receive(:backorderable?).and_return(true)
+        subject.adjust_count_on_hand(- (current_on_hand + 2))
+      end
 
       it "doesn't process backorders" do
         expect(subject).not_to receive(:backordered_inventory_units)

From 20fd3c2642d2abdc262d6dff3d88c1c6c5be6e72 Mon Sep 17 00:00:00 2001
From: Kristina Lim <kristinalim.ph@gmail.com>
Date: Fri, 15 May 2020 01:56:34 +0800
Subject: [PATCH 16/19] Reset negative count on hand in existing non
 backorderable stock items

---
 ...korderable_count_on_hand_in_stock_items.rb | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 db/migrate/20200514174526_reset_negative_nonbackorderable_count_on_hand_in_stock_items.rb

diff --git a/db/migrate/20200514174526_reset_negative_nonbackorderable_count_on_hand_in_stock_items.rb b/db/migrate/20200514174526_reset_negative_nonbackorderable_count_on_hand_in_stock_items.rb
new file mode 100644
index 0000000000..c57730c99a
--- /dev/null
+++ b/db/migrate/20200514174526_reset_negative_nonbackorderable_count_on_hand_in_stock_items.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class ResetNegativeNonbackorderableCountOnHandInStockItems < ActiveRecord::Migration
+  module Spree
+    class StockItem < ActiveRecord::Base
+      self.table_name = "spree_stock_items"
+    end
+  end
+
+  def up
+    Spree::StockItem.where(backorderable: false)
+      .where("count_on_hand < 0")
+      .update_all(count_on_hand: 0)
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

From e12e50aa84b5621bbb2e71ca06206fc4368402c0 Mon Sep 17 00:00:00 2001
From: Luis Ramos <luisramos0@gmail.com>
Date: Mon, 22 Jun 2020 17:55:54 +0100
Subject: [PATCH 17/19] Move rubocop exception to rubocop todo

---
 .rubocop_todo.yml              | 7 +++++++
 app/models/spree/stock_item.rb | 2 --
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 753aaee48e..a0c6a0b30c 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -363,6 +363,13 @@ Rails/UniqueValidationWithoutIndex:
     - 'app/models/customer.rb'
     - 'app/models/exchange.rb'
 
+# Offense count: 2
+# Configuration parameters: Include.
+# Include: app/models/**/*.rb
+Rails/UniqueValidationWithoutIndex:
+  Exclude:
+    - 'app/models/spree/stock_item.rb'
+
 # Offense count: 1
 # Configuration parameters: Environments.
 # Environments: development, test, production
diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index f71df2b942..cf86103453 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -7,9 +7,7 @@ module Spree
     has_many :stock_movements, dependent: :destroy
 
     validates :stock_location, :variant, presence: true
-    # rubocop:disable Rails/UniqueValidationWithoutIndex
     validates :variant_id, uniqueness: { scope: :stock_location_id }
-    # rubocop:enable Rails/UniqueValidationWithoutIndex
     validates :count_on_hand, numericality: { greater_than_or_equal_to: 0, unless: :backorderable? }
 
     attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id

From 34207fc20ffbd5a5463366e573daf4fd06d4ff3d Mon Sep 17 00:00:00 2001
From: Luis Ramos <luisramos0@gmail.com>
Date: Mon, 22 Jun 2020 18:19:05 +0100
Subject: [PATCH 18/19] Bring changes to stock_item from spree 2.1, the
 previous version was from spree 2.0.4

---
 app/models/spree/stock_item.rb | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/app/models/spree/stock_item.rb b/app/models/spree/stock_item.rb
index cf86103453..e6df19b03a 100644
--- a/app/models/spree/stock_item.rb
+++ b/app/models/spree/stock_item.rb
@@ -2,24 +2,23 @@
 
 module Spree
   class StockItem < ActiveRecord::Base
+    acts_as_paranoid
+
     belongs_to :stock_location, class_name: 'Spree::StockLocation'
     belongs_to :variant, class_name: 'Spree::Variant'
     has_many :stock_movements, dependent: :destroy
 
     validates :stock_location, :variant, presence: true
-    validates :variant_id, uniqueness: { scope: :stock_location_id }
+    validates :variant_id, uniqueness: { scope: [:stock_location_id, :deleted_at] }
     validates :count_on_hand, numericality: { greater_than_or_equal_to: 0, unless: :backorderable? }
 
-    attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
-
     delegate :weight, to: :variant
+    delegate :name, to: :variant, prefix: true
 
     def backordered_inventory_units
       Spree::InventoryUnit.backordered_for_stock_item(self)
     end
 
-    delegate :name, to: :variant, prefix: true
-
     def adjust_count_on_hand(value)
       with_lock do
         self.count_on_hand = count_on_hand + value
@@ -38,6 +37,10 @@ module Spree
       in_stock? || backorderable?
     end
 
+    def variant
+      Spree::Variant.unscoped { super }
+    end
+
     private
 
     def count_on_hand=(value)

From ba50491c6d2e6699368aea68259fc99c3089597a Mon Sep 17 00:00:00 2001
From: Luis Ramos <luisramos0@gmail.com>
Date: Mon, 22 Jun 2020 19:28:28 +0100
Subject: [PATCH 19/19] Restructure the spec a little

---
 .../checkout_controller_concurrency_spec.rb   | 33 ++++++++++---------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/spec/controllers/checkout_controller_concurrency_spec.rb b/spec/controllers/checkout_controller_concurrency_spec.rb
index 51eefe98ae..266f9a4fbe 100644
--- a/spec/controllers/checkout_controller_concurrency_spec.rb
+++ b/spec/controllers/checkout_controller_concurrency_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 # This is the first example of testing concurrency in the Open Food Network.
@@ -15,6 +17,20 @@ describe CheckoutController, concurrency: true, type: :controller do
   let(:payment_method) { create(:payment_method, distributors: [distributor]) }
   let(:breakpoint) { Mutex.new }
 
+  let(:address_params) { address.attributes.except("id") }
+  let(:order_params) {
+    {
+      "payments_attributes" => [
+        {
+          "payment_method_id" => payment_method.id,
+          "amount" => order.total
+        }
+      ],
+      "bill_address_attributes" => address_params,
+      "ship_address_attributes" => address_params,
+    }
+  }
+
   before do
     # Create a valid order ready for checkout:
     create(:shipping_method, distributors: [distributor])
@@ -26,7 +42,9 @@ describe CheckoutController, concurrency: true, type: :controller do
     allow(controller).to receive(:spree_current_user).and_return(order.user)
     allow(controller).to receive(:current_distributor).and_return(order.distributor)
     allow(controller).to receive(:current_order_cycle).and_return(order.order_cycle)
+  end
 
+  it "handles two concurrent orders successfully" do
     # New threads start running straight away. The breakpoint is after loading
     # the order and before advancing the order's state and making payments.
     breakpoint.lock
@@ -36,21 +54,6 @@ describe CheckoutController, concurrency: true, type: :controller do
       # I did not find out how to call the original code otherwise.
       ActiveSupport::Notifications.instrument("spree.checkout.update")
     end
-  end
-
-  it "waits for concurrent checkouts" do
-    # Basic data the user submits during checkout:
-    address_params = address.attributes.except("id")
-    order_params = {
-      "payments_attributes" => [
-        {
-          "payment_method_id" => payment_method.id,
-          "amount" => order.total
-        }
-      ],
-      "bill_address_attributes" => address_params,
-      "ship_address_attributes" => address_params,
-    }
 
     # Starting two checkout threads. The controller code will determine if
     # these two threads are synchronised correctly or run into a race condition.