From a31487a86d92d22aaad56845cf5344273eff6a74 Mon Sep 17 00:00:00 2001
From: Matt-Yorkley <9029026+Matt-Yorkley@users.noreply.github.com>
Date: Tue, 23 Mar 2021 19:56:29 +0000
Subject: [PATCH] Clear any legacy taxes when applying tax to an order

#create_tax_charge! adds tax (adjustments) to all taxable items on an order. If an order order has legacy taxes (lump-sum tax adjustments on the order object), we remove them here before re-applying taxes (using the new setup).
---
 app/models/spree/order.rb | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/app/models/spree/order.rb b/app/models/spree/order.rb
index 817a0d716b..556b8b0c13 100644
--- a/app/models/spree/order.rb
+++ b/app/models/spree/order.rb
@@ -293,6 +293,8 @@ module Spree
     # Creates new tax charges if there are any applicable rates. If prices already
     # include taxes then price adjustments are created instead.
     def create_tax_charge!
+      clear_legacy_taxes!
+
       Spree::TaxRate.adjust(self, line_items)
       Spree::TaxRate.adjust(self, shipments) if shipments.any?
       Spree::TaxRate.adjust(self, all_adjustments.enterprise_fee)
@@ -592,6 +594,13 @@ module Spree
       @fee_handler ||= OrderFeesHandler.new(self)
     end
 
+    def clear_legacy_taxes!
+      # For instances that use additional taxes, old orders can have taxes recorded in
+      # lump-sum amounts per-order. We clear them here before re-applying the order's taxes,
+      # which will now be applied per-item.
+      adjustments.tax.additional.delete_all
+    end
+
     def process_each_payment
       raise Core::GatewayError, Spree.t(:no_pending_payments) if pending_payments.empty?