fix after code review

Author: silinmykola

app/code/Magento/Catalog/Ui/DataProvider/CatalogEavValidationRules.php

@@ -38,14 +38,20 @@ public function build(ProductAttributeInterface $attribute, array $data)
 
         foreach ($validationClasses as $class) {
             if (preg_match('/^maximum-length-(\d+)$/', $class, $matches)) {
-                $rules['max_text_length'] = $matches[1];
+                $rules['max_text_length'][] = $matches[1];
                 continue;
             }
             if (preg_match('/^minimum-length-(\d+)$/', $class, $matches)) {
-                $rules['min_text_length'] = $matches[1];
+                $rules['min_text_length'][] = $matches[1];
                 continue;
             }
 
+            if (isset($rules['max_text_length'])) {
+                $rules['max_text_length'] = array_merge([], ...$rules['max_text_length']);
+            }
+            if (isset($rules['min_text_length'])) {
+                $rules['min_text_length'] = array_merge([], ...$rules['min_text_length']);
+            }
             $rules = $this->mapRules($class, $rules);
         }
 

app/code/Magento/Tax/Model/Calculation/RateRepository.php

@@ -272,7 +272,7 @@ private function validate(\Magento\Tax\Api\Data\TaxRateInterface $taxRate)
             );
         }
 
-        if ($taxRate->getCode() !== null
+        if ($taxRate->getCode() === null
             || !\Zend_Validate::is(trim($taxRate->getCode()), 'NotEmpty')
         ) {
             $exception->addError(__('"%fieldName" is required. Enter and try again.', ['fieldName' => 'code']));
@@ -297,7 +297,7 @@ private function validate(\Magento\Tax\Api\Data\TaxRateInterface $taxRate)
                 $exception->addError(__('Range To should be equal or greater than Range From.'));
             }
         } else {
-            if ($taxRate->getTaxPostcode() !== null
+            if ($taxRate->getTaxPostcode() === null
                 || !\Zend_Validate::is(trim($taxRate->getTaxPostcode()), 'NotEmpty')
             ) {
                 $exception->addError(