Fix SKU limit in import new products for 2.3 with backward compatible allow 64 characters

Author: ravi-chandra3197

app/code/Magento/CatalogImportExport/Model/Import/Product/Validator.php

@@ -153,7 +153,12 @@ public function isRequiredAttributeValid($attrCode, array $attributeParams, arra
             $doCheck = true;
         }
 
-        return $doCheck ? isset($rowData[$attrCode]) && strlen(trim($rowData[$attrCode])) : true;
+        if ($doCheck === true) {
+            return isset($rowData[$attrCode])
+                && strlen(trim($rowData[$attrCode]))
+                && trim($rowData[$attrCode]) !== $this->context->getEmptyAttributeValueConstant();
+        }
+        return true;
     }
 
     /**
@@ -191,6 +196,11 @@ public function isAttributeValid($attrCode, array $attrParams, array $rowData)
         if (!strlen(trim($rowData[$attrCode]))) {
             return true;
         }
+
+        if ($rowData[$attrCode] === $this->context->getEmptyAttributeValueConstant() && !$attrParams['is_required']) {
+            return true;
+        }
+
         switch ($attrParams['type']) {
             case 'varchar':
             case 'text':
@@ -212,6 +222,12 @@ public function isAttributeValid($attrCode, array $attrParams, array $rowData)
                         break;
                     }
                 }
+
+                $uniqueValues = array_unique($values);
+                if (count($uniqueValues) != count($values)) {
+                    $valid = false;
+                    $this->_addMessages([RowValidatorInterface::ERROR_DUPLICATE_MULTISELECT_VALUES]);
+                }
                 break;
             case 'datetime':
                 $val = trim($rowData[$attrCode]);
@@ -328,4 +344,4 @@ public function init($context)
             $validator->init($context);
         }
     }
-}
+}