ACP2E-1295: VAT is not applied to billing address without a VAT ID

- with test

Author: arnobsh

app/code/Magento/Customer/Observer/AfterAddressSaveObserver.php

@@ -34,7 +34,7 @@ class AfterAddressSaveObserver implements ObserverInterface
     /**
      * VAT ID validation processed flag code
      */
-    const VIV_PROCESSED_FLAG = 'viv_after_address_save_processed';
+    public const VIV_PROCESSED_FLAG = 'viv_after_address_save_processed';
 
     /**
      * @var HelperAddress
@@ -141,8 +141,7 @@ public function execute(Observer $observer)
             if ($customerAddress->getVatId() == ''
                 || !$this->_customerVat->isCountryInEU($customerAddress->getCountry())
             ) {
-                $defaultGroupId = $customer->getGroupId() ? $customer->getGroupId() :
-                    $this->_groupManagement->getDefaultGroup($customer->getStore())->getId();
+                $defaultGroupId = $this->_groupManagement->getDefaultGroup($customer->getStore())->getId();
                 if (!$customer->getDisableAutoGroupChange() && $customer->getGroupId() != $defaultGroupId) {
                     $customer->setGroupId($defaultGroupId);
                     $customer->save();

app/code/Magento/Customer/Test/Unit/Observer/AfterAddressSaveObserverTest.php

@@ -129,15 +129,15 @@ protected function setUp(): void
      * @param bool $processedFlag
      * @param bool $forceProcess
      * @param int $addressId
-     * @param int $registeredAddressId
-     * @param string $configAddressType
+     * @param mixed $registeredAddressId
+     * @param mixed $configAddressType
      * @dataProvider dataProviderAfterAddressSaveRestricted
      */
     public function testAfterAddressSaveRestricted(
-        $isVatValidationEnabled,
-        $processedFlag,
-        $forceProcess,
-        $addressId,
+        bool $isVatValidationEnabled,
+        bool $processedFlag,
+        bool $forceProcess,
+        int  $addressId,
         $registeredAddressId,
         $configAddressType
     ) {
@@ -303,17 +303,21 @@ public function testAfterAddressSaveException()
     }
 
     /**
-     * @param string $vatId
+     * @param mixed $vatId
      * @param int $countryId
      * @param bool $isCountryInEU
+     * @param int $customerGroupId
      * @param int $defaultGroupId
+     * @param bool $disableAutoGroupChange
      * @dataProvider dataProviderAfterAddressSaveDefaultGroup
      */
     public function testAfterAddressSaveDefaultGroup(
         $vatId,
-        $countryId,
-        $isCountryInEU,
-        $defaultGroupId
+        int    $countryId,
+        bool   $isCountryInEU,
+        int $customerGroupId,
+        int $defaultGroupId,
+        bool $disableAutoGroupChange
     ) {
         $store = $this->getMockBuilder(Store::class)
             ->disableOriginalConstructor()
@@ -340,15 +344,15 @@ public function testAfterAddressSaveDefaultGroup(
             ->willReturn($store);
         $customer->expects($this->once())
             ->method('getDisableAutoGroupChange')
-            ->willReturn(false);
-        $customer->expects($this->exactly(2))
+            ->willReturn($disableAutoGroupChange);
+        $customer->expects($this->any())
             ->method('getGroupId')
-            ->willReturn(null);
-        $customer->expects($this->once())
+            ->willReturn($customerGroupId);
+        $customer->expects($this->any())
             ->method('setGroupId')
             ->with($defaultGroupId)
             ->willReturnSelf();
-        $customer->expects($this->once())
+        $customer->expects($this->any())
             ->method('save')
             ->willReturnSelf();
 
@@ -408,14 +412,17 @@ public function testAfterAddressSaveDefaultGroup(
     public function dataProviderAfterAddressSaveDefaultGroup()
     {
         return [
-            ['', 1, false, 1],
-            [1, 1, false, 1],
+            'when vatId is empty, non EU country and disable auto group false' => ['', 1, false, 1, 1, false],
+            'when vatId is empty, non EU country and disable auto group true' => ['', 1, false, 1, 1, true],
+            'when vatId is empty, non EU country, disable auto group true
+            and different groupId' => ['', 1, false, 1, 2, true],
+            'when vatId is not empty, non EU country and disable auto group false' => [1, 1, false, 1, 1, false],
         ];
     }
 
     /**
-     * @param string $vatId
-     * @param $vatClass
+     * @param mixed $vatId
+     * @param mixed $vatClass
      * @param int $countryId
      * @param string $country
      * @param int $newGroupId
@@ -432,15 +439,15 @@ public function dataProviderAfterAddressSaveDefaultGroup()
     public function testAfterAddressSaveNewGroup(
         $vatId,
         $vatClass,
-        $countryId,
-        $country,
-        $newGroupId,
-        $areaCode,
-        $resultVatIsValid,
-        $resultRequestSuccess,
-        $resultValidMessage,
-        $resultInvalidMessage,
-        $resultErrorMessage
+        int    $countryId,
+        string $country,
+        int    $newGroupId,
+        string $areaCode,
+        bool   $resultVatIsValid,
+        bool   $resultRequestSuccess,
+        string $resultValidMessage,
+        string $resultInvalidMessage,
+        string $resultErrorMessage
     ) {
         $store = $this->getMockBuilder(Store::class)
             ->disableOriginalConstructor()