Moved the Totals Collector earlier in the stack, just after the discounts have been applied.

Author: gwharton

Model/Collector/AutoCustomerGroup.php

@@ -13,9 +13,23 @@
 use Gw\AutoCustomerGroup\Model\AutoCustomerGroup as AutoCustomerGroupModel;
 
 /**
- * AutoCustomerGroup totals collector, configured from sales.xml which runs at the end of the stack
- * of collectors. If the group has changed, then the tax collectors must be re-run as the tax to be
- * applied will now be different. The collectors to be rerun can be configured in di.xml
+ * Magento Vanilla Collectors sequence
+ *
+ * 100  Magento\Quote\Model\Quote\Address\Total\Subtotal
+ * 200  Magento\Tax\Model\Sales\Total\Quote\Subtotal
+ * 225  Magento\Weee\Model\Total\Quote\Weee
+ * 300  Magento\SalesRule\Model\Quote\Discount
+ * 325  <-- This is a good place for us to be. Product discounts already applied
+ * 350  Magento\Quote\Model\Quote\Address\Total\Shipping
+ * 375  Magento\Tax\Model\Sales\Total\Quote\Shipping
+ * 400  Magento\SalesRule\Model\Quote\Address\Total\ShippingDiscount
+ * 450  Magento\Tax\Model\Sales\Total\Quote\Tax
+ * 460  Magento\Weee\Model\Total\Quote\WeeeTax
+ * 550  Magento\Quote\Model\Quote\Address\Total\Grand
+ * AutoCustomerGroup totals collector, configured from sales.xml
+ * What happens if we switch groups to a group where discount no longer applies? Should we re-run
+ * the discount collectors, what if that then changes the order total. We need to re-evaluate groups again.
+ * For now, lets just re-run all collectors that came before us, and carry on
  * @SuppressWarnings(PHPMD.CookieAndSessionMisuse)
  */
 class AutoCustomerGroup extends AbstractTotal
@@ -227,9 +241,10 @@ private function updateGroup($newGroup, Quote $quote, $customer, $shippingAssign
             );
             $quote->setCustomerGroupId($newGroup);
 
-            //The group has changed. We need to rerun the Tax collectors.
-            foreach ($this->additionalCollectors as $collector) {
+            //The group has changed. Which collectors should we re-run
+            foreach ($this->additionalCollectors as $code => $collector) {
                 if ($collector) {
+                    $collector->setCode($code);
                     $collector->collect($quote, $shippingAssignment, $total);
                 }
             }

etc/di.xml

@@ -11,10 +11,10 @@
     <type name="Gw\AutoCustomerGroup\Model\Collector\AutoCustomerGroup">
         <arguments>
             <argument name="additionalCollectors" xsi:type="array">
-                <item name="redo_tax_subtotal" xsi:type="object">Magento\Tax\Model\Sales\Total\Quote\Subtotal</item>
-                <item name="redo_tax_shipping" xsi:type="object">Magento\Tax\Model\Sales\Total\Quote\Shipping</item>
-                <item name="redo_tax" xsi:type="object">Magento\Tax\Model\Sales\Total\Quote\Tax</item>
-                <item name="redo_tax_weee_tax" xsi:type="object">Magento\Weee\Model\Total\Quote\WeeeTax</item>
+                <item name="subtotal" xsi:type="object">Magento\Quote\Model\Quote\Address\Total\Subtotal</item>
+                <item name="tax_subtotal" xsi:type="object">Magento\Tax\Model\Sales\Total\Quote\Subtotal</item>
+                <item name="weee" xsi:type="object">Magento\Weee\Model\Total\Quote\Weee</item>
+                <item name="discount" xsi:type="object">Magento\SalesRule\Model\Quote\Discount</item>
             </argument>
         </arguments>
     </type>

etc/sales.xml

@@ -2,7 +2,7 @@
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Sales:etc/sales.xsd">
     <section name="quote">
         <group name="totals">
-            <item name="autocustomergroup" instance="Gw\AutoCustomerGroup\Model\Collector\AutoCustomerGroup" sort_order="1000"/>
+            <item name="autocustomergroup" instance="Gw\AutoCustomerGroup\Model\Collector\AutoCustomerGroup" sort_order="325"/>
         </group>
     </section>
 </config>