AC-3160: Fix possible deprecation issues with 8.1

Author: karyna-t

lib/internal/Magento/Framework/Backup/Media.php

@@ -65,7 +65,9 @@ protected function _prepareIgnoreList()
             foreach (new \DirectoryIterator($path) as $item) {
                 $filename = $item->getFilename();
                 if (!$item->isDot() && !in_array($filename, $whiteList)) {
-                    $this->addIgnorePaths(str_replace('\\', '/', $item->getPathname()));
+                    $this->addIgnorePaths(
+                        str_replace('\\', '/', $item->getPathname() !== null ? $item->getPathname() : '')
+                    );
                 }
             }
         }

lib/internal/Magento/Framework/Cache/Backend/Decorator/Compression.php

@@ -16,7 +16,7 @@ class Compression extends \Magento\Framework\Cache\Backend\Decorator\AbstractDec
     /**
      * Prefix of compressed strings
      */
-    const COMPRESSION_PREFIX = 'CACHE_COMPRESSION';
+    public const COMPRESSION_PREFIX = 'CACHE_COMPRESSION';
 
     /**
      * Array of specific options. Made in separate array to distinguish from parent options
@@ -50,18 +50,17 @@ public function load($cacheId, $noTestCacheValidity = false)
      * Note : $data is always "string" (serialization is done by the
      * core not by the backend)
      *
-     * @param string $data              Datas to cache
-     * @param string $cacheId           Cache id
-     * @param string[] $tags            Array of strings, the cache record will be tagged by each string entry
-     * @param bool $specificLifetime    If != false, set a specific lifetime for this cache record
-     *                                  (null => infinite lifetime)
-     * @param int $priority             integer between 0 (very low priority) and 10 (maximum priority) used by
-     *                                  some particular backends
+     * @param string $data Datas to cache
+     * @param string $cacheId Cache id
+     * @param string[] $tags Array of strings, the cache record will be tagged by each string entry
+     * @param bool $specificLifetime If != false, set a specific lifetime for this cache record
+     * (null => infinite lifetime)
+     * @param int $priority integer between 0 (very low priority) and 10 (max priority) used by some particular backends
      * @return bool true if no problem
      */
     public function save($data, $cacheId, $tags = [], $specificLifetime = false, $priority = 8)
     {
-        if ($this->_isCompressionNeeded($data)) {
+        if ($data !== null && $this->_isCompressionNeeded($data)) {
             $data = self::_compressData($data);
         }
 

lib/internal/Magento/Framework/Code/Reader/NamespaceResolver.php

@@ -14,7 +14,7 @@ class NamespaceResolver
     /**
      * Namespace separator
      */
-    const NS_SEPARATOR = '\\';
+    public const NS_SEPARATOR = '\\';
 
     /**
      * @var ScalarTypesProvider
@@ -44,9 +44,9 @@ public function __construct(ScalarTypesProvider $scalarTypesProvider = null)
      */
     public function resolveNamespace($type, array $availableNamespaces)
     {
-        if (substr($type, 0, 1) !== self::NS_SEPARATOR
+        if (!empty($type)
+            && substr($type, 0, 1) !== self::NS_SEPARATOR
             && !in_array($type, $this->scalarTypesProvider->getTypes())
-            && !empty($type)
         ) {
             $name = explode(self::NS_SEPARATOR, $type);
             $unqualifiedName = $name[0];