AC-3108: Fix possible deprecation issues with 8.1

Author: karyna-t

app/code/Magento/Persistent/Model/Persistent/Config.php

@@ -106,7 +106,7 @@ public function setConfigFilePath($path)
     protected function _getConfigDomXPath()
     {
         if ($this->_configDomXPath === null) {
-            $dir = explode("/", $this->_configFilePath);
+            $dir = $this->_configFilePath !== null ? explode("/", $this->_configFilePath) : [];
             array_pop($dir);
             $dir = implode("/", $dir);
             $directoryRead = $this->readFactory->create($dir);

app/code/Magento/ProductAlert/Controller/Add/Price.php

@@ -61,7 +61,7 @@ public function __construct(
      */
     protected function isInternal($url)
     {
-        if (strpos($url, 'http') === false) {
+        if ($url === null || strpos($url, 'http') === false) {
             return false;
         }
         $currentStore = $this->storeManager->getStore();

app/code/Magento/Quote/Model/ResourceModel/Quote/Address/Attribute/Frontend/Discount.php

@@ -24,7 +24,7 @@ public function fetchTotals(\Magento\Quote\Model\Quote\Address $address)
         if ($amount != 0) {
             $title = __('Discount');
             $couponCode = $address->getQuote()->getCouponCode();
-            if (strlen($couponCode)) {
+            if ($couponCode !== null && strlen($couponCode)) {
                 $title .= sprintf(' (%s)', $couponCode);
             }
             $address->addTotal(['code' => 'discount', 'title' => $title, 'value' => -$amount]);

app/code/Magento/QuoteGraphQl/Model/CartItem/DataProvider/CustomizableOptionValue/Multiple.php

@@ -55,7 +55,7 @@ public function getData(
         SelectedOption $selectedOption
     ): array {
         $selectedOptionValueData = [];
-        $optionIds = explode(',', $selectedOption->getValue());
+        $optionIds = $selectedOption->getValue() !== null ? explode(',', $selectedOption->getValue()) : [];
 
         if (0 === count($optionIds)) {
             return $selectedOptionValueData;

app/code/Magento/QuoteGraphQl/Model/Resolver/CartPrices.php

@@ -130,7 +130,7 @@ private function getDiscount(Total $total, string $currency)
             return null;
         }
         return [
-            'label' => explode(', ', $total->getDiscountDescription()),
+            'label' => $total->getDiscountDescription() !== null ? explode(', ', $total->getDiscountDescription()) : [],
             'amount' => ['value' => $total->getDiscountAmount(), 'currency' => $currency]
         ];
     }

app/code/Magento/QuoteGraphQl/Model/Resolver/CustomizableOptions.php

@@ -51,7 +51,8 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
         }
 
         $customizableOptionsData = [];
-        $customizableOptionIds = explode(',', $quoteItemOption->getValue());
+        $customizableOptionIds = $quoteItemOption->getValue() !== null ?
+            explode(',', $quoteItemOption->getValue()) : [];
 
         foreach ($customizableOptionIds as $customizableOptionId) {
             $customizableOption = $this->customizableOption->getData(

app/code/Magento/QuoteGraphQl/Test/Unit/Model/Resolver/CartPricesTest.php

@@ -124,7 +124,6 @@ public function testResolve(): void
             ->expects($this->once())
             ->method('getSubtotalInclTax');
         $this->totalMock
-            ->expects($this->once())
             ->method('getDiscountDescription')
             ->willReturn('Discount Description');
         $this->totalMock

app/code/Magento/ReleaseNotification/Ui/DataProvider/Modifier/Notifications.php

@@ -197,7 +197,8 @@ private function getNotificationContent()
     {
         $version = strtolower($this->getTargetVersion());
         $edition = strtolower($this->productMetadata->getEdition());
-        $locale = strtolower($this->session->getUser()->getInterfaceLocale());
+        $locale = $this->session->getUser()->getInterfaceLocale();
+        $locale = $locale !== null ? strtolower($locale) : '';
 
         $cacheKey = self::$cachePrefix . $version . "-" . $edition . "-" . $locale;
         $modalContent = $this->cacheStorage->load($cacheKey);

app/code/Magento/ReleaseNotification/Ui/Renderer/NotificationRenderer.php

@@ -146,7 +146,7 @@ private function buildSubHeadings(array $subHeadings)
             $content .= $this->escaper->escapeHtml($subHeading['title']);
             $content .= "</h3>";
             $content .= "<p>";
-            $content .= $this->formatContentWithLinks($subHeading['content']);
+            $content .= isset($subHeading['content']) ? $this->formatContentWithLinks($subHeading['content']) : '';
             $content .= "</p>";
             $content .= "</div>";
         }
@@ -170,6 +170,8 @@ private function buildFooter(array $footer)
     }
 
     /**
+     * Formats links in the content to a correct format.
+     *
      * Searches a given string for a URL, formats it to an HTML anchor tag, and returns the original string in the
      * correct HTML format.
      *

app/code/Magento/Tax/Model/TaxClass/Repository.php

@@ -184,7 +184,7 @@ protected function validateTaxClassData(\Magento\Tax\Api\Data\TaxClassInterface
         }
 
         $classType = $taxClass->getClassType();
-        if (!\Zend_Validate::is(trim($classType), 'NotEmpty')) {
+        if (!\Zend_Validate::is($classType !== null ? trim($classType) : '', 'NotEmpty')) {
             $exception->addError(
                 __('"%fieldName" is required. Enter and try again.', ['fieldName' => ClassModel::KEY_TYPE])
             );