Tax Categories on Line Items respect updates to Variant and Product Tax Categories

core/app/models/spree/line_item.rb

@@ -36,6 +36,7 @@ class LineItem < Spree::Base
     before_destroy :destroy_inventory_units
 
     delegate :name, :description, :sku, :should_track_inventory?, to: :variant
+    delegate :tax_category, :tax_category_id, to: :variant, prefix: true
     delegate :currency, to: :order, allow_nil: true
 
     attr_accessor :target_shipment, :price_currency
@@ -128,6 +129,24 @@ def pricing_options
       Spree::Config.pricing_options_class.from_line_item(self)
     end
 
+    # @return [Spree::TaxCategory] the variant's tax category
+    #
+    # This returns the variant's tax category if the tax category ID on the line_item is nil. It looks
+    # like an association, but really is an override.
+    #
+    def tax_category
+      super || variant_tax_category
+    end
+
+    # @return [Integer] the variant's tax category ID
+    #
+    # This returns the variant's tax category ID if the tax category ID on the line_id is nil. It looks
+    # like an association, but really is an override.
+    #
+    def tax_category_id
+      super || variant_tax_category_id
+    end
+
     private
 
     # Sets the quantity to zero if it is nil or less than zero.

core/app/models/spree/order_taxation.rb

@@ -28,6 +28,7 @@ def apply(taxes)
 
       @order.line_items.each do |item|
         taxed_items = taxes.line_item_taxes.select { |element| element.item_id == item.id }
+        item.tax_category_id = item.variant_tax_category_id
         update_adjustments(item, taxed_items)
       end
 

core/app/models/spree/tax/tax_helpers.rb

@@ -5,11 +5,22 @@ module Tax
     module TaxHelpers
       private
 
+      # Select active rates matching tax category and address
+      #
+      # @private
+      # @param [Spree::LineItem, Spree::Shipment, Spree::ShippingRate] item
+      #   the line item, shipment, or shipping rate to select rates for
+      # @return [Array<Spree::TaxRate>] the active Tax Rates that match both
+      #   Tax Category and the item's order's tax address
       def rates_for_item(item)
         @rates_for_item ||= Spree::TaxRate.item_level.for_address(item.order.tax_address)
+        # try is used here to ensure that a LineItem has rates selected for the
+        # currently configured Tax Category. Shipments and ShippingRates do not
+        # implement variant_tax_category_id, so try is necessary instead of .&
+        tax_category_id = item.try(:variant_tax_category_id) || item.tax_category_id
 
         @rates_for_item.select do |rate|
-          rate.active? && rate.tax_categories.map(&:id).include?(item.tax_category_id)
+          rate.active? && rate.tax_categories.map(&:id).include?(tax_category_id)
         end
       end
     end

core/app/models/spree/tax_calculator/default.rb

@@ -99,7 +99,7 @@ def calculate_rates(item)
       # @return [Array<Spree::TaxRate>] rates that apply to an order
       def rates_for_order
         tax_category_ids = Set[
-          *@order.line_items.map(&:tax_category_id),
+          *@order.line_items.map(&:variant_tax_category_id),
           *@order.shipments.map(&:tax_category_id)
         ]
         rates = Spree::TaxRate.active.order_level.for_address(@order.tax_address)

core/app/models/spree/variant.rb

@@ -35,7 +35,7 @@ class Variant < Spree::Base
     delegate :name, :description, :slug, :available_on, :discontinue_on, :discontinued?,
              :meta_description, :meta_keywords,
              to: :product
-    delegate :tax_category, to: :product, prefix: true
+    delegate :tax_category, :tax_category_id, to: :product, prefix: true
     delegate :shipping_category, :shipping_category_id,
       to: :product, prefix: true
     delegate :tax_rates, to: :tax_category
@@ -150,6 +150,15 @@ def tax_category
       super || product_tax_category
     end
 
+    # @return [Integer] the variant's tax category ID
+    #
+    # This returns the product's tax category ID if the tax category ID on the variant is nil. It looks
+    # like an association, but really is an override.
+    #
+    def tax_category_id
+      super || product_tax_category_id
+    end
+
     # @return [Spree::ShippingCategory] the variant's shipping category
     #
     # This returns the product's shipping category if the shipping category ID on the variant is nil. It looks

core/lib/spree/testing_support/factories/order_factory.rb

@@ -43,7 +43,15 @@
         evaluator.stock_location # must evaluate before creating line items
 
         evaluator.line_items_attributes.each do |attributes|
-          attributes = { order:, price: evaluator.line_items_price }.merge(attributes)
+          attributes = { order:, price: evaluator.line_items_price }.merge(attributes).tap do |attrs|
+            tax_category = attributes.delete(:tax_category)
+            if attrs[:variant] && tax_category
+              attrs[:variant].update(tax_category: )
+            elsif tax_category
+              attrs[:variant] = create(:variant, tax_category: )
+            end
+          end
+
           create(:line_item, attributes)
         end
         order.line_items.reload

core/spec/models/spree/line_item_spec.rb

@@ -5,6 +5,7 @@
 RSpec.describe Spree::LineItem, type: :model do
   let(:order) { create :order_with_line_items, line_items_count: 1 }
   let(:line_item) { order.line_items.first }
+  let(:target_shipment) { Spree::Shipment.new }
 
   context '#destroy' do
     it "fetches soft-deleted products" do
@@ -18,7 +19,8 @@
     end
 
     it "returns inventory when a line item is destroyed" do
-      expect_any_instance_of(Spree::OrderInventory).to receive(:verify)
+      line_item.target_shipment = target_shipment
+      expect_any_instance_of(Spree::OrderInventory).to receive(:verify).with(target_shipment)
       line_item.destroy
     end
 
@@ -30,8 +32,8 @@
   context "#save" do
     context "target_shipment is provided" do
       it "verifies inventory" do
-        line_item.target_shipment = Spree::Shipment.new
-        expect_any_instance_of(Spree::OrderInventory).to receive(:verify)
+        line_item.target_shipment = target_shipment
+        expect_any_instance_of(Spree::OrderInventory).to receive(:verify).with(target_shipment)
         line_item.save
       end
     end

core/spec/models/spree/order_taxation_spec.rb

@@ -26,14 +26,19 @@
       :product,
       price: 20,
       name: "Book",
-      tax_category: books_category,
+      tax_category: create(:tax_category),
     )
   end
 
   let(:taxation) { described_class.new(order) }
 
+  before do
+    order.contents.add(book.master)
+    book.update(tax_category: books_category)
+  end
+
   describe "#apply" do
-    let(:line_item) { order.contents.add(book.master) }
+    let(:line_item) { order.line_items.first }
 
     let(:line_item_tax) do
       Spree::Tax::ItemTax.new(
@@ -53,9 +58,16 @@
       )
     end
 
-    before { taxation.apply(taxes) }
+    subject(:apply) { taxation.apply(taxes) }
+
+    it "updates the line_item's tax_category_id" do
+      expect { apply }.to change {
+        line_item[:tax_category_id]
+      }.to(books_category.id)
+    end
 
     it "creates a new tax adjustment", aggregate_failures: true do
+      apply
       expect(line_item.adjustments.count).to eq 1
 
       tax_adjustment = line_item.adjustments.first
@@ -66,6 +78,8 @@
     end
 
     context "when new taxes are applied" do
+      before { apply }
+
       let(:new_line_item_tax) do
         Spree::Tax::ItemTax.new(
           item_id: line_item.id,
@@ -108,6 +122,8 @@
     end
 
     context "when taxes are removed" do
+      before { apply }
+
       let(:new_taxes) do
         Spree::Tax::OrderTax.new(
           order_id: order.id,
@@ -126,6 +142,8 @@
     end
 
     context "with order-level taxes" do
+      before { apply }
+
       let(:delivery_fee) do
         FactoryBot.create(
           :tax_rate,

core/spec/models/spree/tax/tax_helpers_spec.rb

@@ -16,17 +16,20 @@ def valid_rates(item)
   let(:tax_category) { create(:tax_category) }
   let(:irrelevant_tax_category) { create(:tax_category) }
 
-  let(:item) { create(:line_item, tax_category:) }
+  let(:item) { create(:line_item, variant:) }
+  let(:variant) { create(:variant, tax_category:) }
   let(:tax_address) { item.order.tax_address }
   let(:zone) { create(:zone, name: "Country Zone", countries: [tax_address.country]) }
 
   let!(:tax_rate) do
     create(:tax_rate, tax_categories: [tax_category], zone:)
   end
 
+  subject { DummyClass.new.valid_rates(item) }
+
   describe '#rates_for_item' do
     it 'returns tax rates that match the tax category of the given item' do
-      expect(DummyClass.new.valid_rates(item)).to contain_exactly(tax_rate)
+      expect(subject).to contain_exactly(tax_rate)
     end
 
     context 'when multiple rates exist that are currently not valid' do
@@ -41,7 +44,40 @@ def valid_rates(item)
       it 'returns only active rates that match the tax category of given item' do
         expect(Spree::TaxRate.for_address(tax_address)).to contain_exactly(tax_rate, invalid_tax_rate)
 
-        expect(DummyClass.new.valid_rates(item)).to contain_exactly(tax_rate)
+        expect(subject).to contain_exactly(tax_rate)
+      end
+    end
+
+    context "when the line_item's variant's tax_category is changed" do
+      let(:new_tax_category) { create(:tax_category) }
+      before do
+        variant.update(tax_category: new_tax_category)
+        tax_rate.update(tax_categories: [new_tax_category])
+      end
+
+      it "returns the new tax rate for the variant's tax category" do
+        expect(subject).to contain_exactly(tax_rate)
+      end
+    end
+
+    context "when item is a shipping_rate" do
+      let(:item) { create(:shipping_rate, shipping_method:) }
+      let(:shipping_method) { create(:shipping_method, tax_category:) }
+
+      it "returns the tax rate for the shipping_method's tax category" do
+        expect(subject).to contain_exactly(tax_rate)
+      end
+
+      context "when the shipping_method's tax_category is changed" do
+        let(:new_tax_category) { create(:tax_category) }
+        before do
+          shipping_method.update(tax_category: new_tax_category)
+          tax_rate.update(tax_categories: [new_tax_category])
+        end
+
+        it "returns the new tax rate for the shipping_method's tax category" do
+          expect(subject).to contain_exactly(tax_rate)
+        end
       end
     end
   end