Sales tax report pulls sales tax from adjustments instead of recalculating it at report-time

app/models/spree/adjustment_decorator.rb

@@ -3,5 +3,6 @@ module Spree
     has_one :metadata, class_name: 'AdjustmentMetadata', dependent: :destroy
 
     scope :enterprise_fee, where(originator_type: 'EnterpriseFee')
+    scope :included_tax, where(originator_type: 'Spree::TaxRate', adjustable_type: 'Spree::LineItem')
   end
 end

lib/open_food_network/sales_tax_report.rb

@@ -34,11 +34,11 @@ module OpenFoodNetwork
         totals[:items] += line_item.quantity
         totals[:items_total] += line_item.amount
 
-        tax_rate = tax_rate_on line_item
+        sales_tax = tax_included_in line_item
 
-        if tax_rate != nil && tax_rate != 0
+        if sales_tax > 0
           totals[:taxable_total] += line_item.amount
-          totals[:sales_tax] += (line_item.amount * tax_rate / (1 + tax_rate)).round(2)
+          totals[:sales_tax] += sales_tax
         end
       end
 
@@ -58,8 +58,8 @@ module OpenFoodNetwork
       end
     end
 
-    def tax_rate_on(line_item)
-      Spree::TaxRate.find_by_tax_category_id(line_item.variant.product.tax_category_id).andand.amount
+    def tax_included_in(line_item)
+      line_item.adjustments.included_tax.sum &:amount
     end
 
     def shipment_inc_vat

spec/features/admin/reports_spec.rb

@@ -99,7 +99,7 @@ feature %q{
     page.should have_content 'Payment State'
   end
   
-  describe "Sales Tax report" do
+  describe "Sales tax report" do
     let(:user1) do
       create_enterprise_user(enterprises: [create(:distributor_enterprise)])
     end
@@ -118,7 +118,9 @@ feature %q{
     let(:order1) { create(:order, distributor: user1.enterprises.first, shipping_method: shipping_method, bill_address: create(:address)) }
     let!(:line_item1) { create(:line_item, variant: product1.master, price: 12.54, quantity: 1, order: order1) }
     let!(:line_item2) { create(:line_item, variant: product2.master, price: 500.15, quantity: 3, order: order1) }
-    let!(:adjustment) { create(:adjustment, adjustable: order1, label: "Shipping", amount: 100.55) }
+
+    let!(:adj_shipping) { create(:adjustment, adjustable: order1, label: "Shipping", amount: 100.55) }
+    let!(:adj_li2_tax) { create(:adjustment, adjustable: line_item2, source: line_item2, originator: tax_rate2, label: "RandomTax", amount: 123.00) }
 
     before do
       Spree::Config.shipment_inc_vat = true
@@ -145,11 +147,12 @@ feature %q{
       # And the totals and sales tax should be correct
       page.should have_content "1512.99" # items total
       page.should have_content "1500.45" # taxable items total
-      page.should have_content "250.08" # sales tax
+      page.should have_content "123.0" # sales tax (from adj_li2_tax, not calculated on the fly)
+      page.should_not have_content "250.08" # the number that would have been calculated on the fly
 
       # And the shipping cost and tax should be correct
-      page.should have_content "100.55" #shipping cost
-      page.should have_content "16.76" #shipping tax
+      page.should have_content "100.55" # shipping cost
+      page.should have_content "16.76" # shipping tax  # TODO: do not calculate on the fly
     end
   end
 

spec/lib/open_food_network/sales_tax_report_spec.rb

@@ -10,7 +10,7 @@ module OpenFoodNetwork
       let(:totals) { report.send(:totals_of, [li1, li2]) }
 
       before do
-        report.stub(:tax_rate_on) { 0.2 }
+        report.stub(:tax_included_in).and_return(2, 4)
       end
 
       it "calculates total quantity" do
@@ -31,7 +31,7 @@ module OpenFoodNetwork
 
       context "when there is no tax on a line item" do
         before do
-          report.stub(:tax_rate_on) { nil }
+          report.stub(:tax_included_in) { 0 }
         end
 
         it "does not appear in taxable total" do