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

Author: ravi-chandra3197

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

@@ -71,7 +71,7 @@ protected function textValidation($attrCode, $type)
         if ($type == 'text') {
             $valid = $this->string->strlen($val) < Product::DB_MAX_TEXT_LENGTH;
         } else if ($attrCode == Product::COL_SKU) {
-            $valid = $this->string->strlen($val) < SKU::SKU_MAX_LENGTH;
+            $valid = $this->string->strlen($val) <= SKU::SKU_MAX_LENGTH;
         } else {
             $valid = $this->string->strlen($val) < Product::DB_MAX_VARCHAR_LENGTH;
         }
@@ -153,12 +153,7 @@ public function isRequiredAttributeValid($attrCode, array $attributeParams, arra
             $doCheck = true;
         }
 
-        if ($doCheck === true) {
-            return isset($rowData[$attrCode])
-                && strlen(trim($rowData[$attrCode]))
-                && trim($rowData[$attrCode]) !== $this->context->getEmptyAttributeValueConstant();
-        }
-        return true;
+        return $doCheck ? isset($rowData[$attrCode]) && strlen(trim($rowData[$attrCode])) : true;
     }
 
     /**
@@ -196,11 +191,6 @@ 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 ($attrParams['type']) {
             case 'varchar':
             case 'text':
@@ -222,12 +212,6 @@ public function isAttributeValid($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]);