Bug fix update attributes

Author: manuelson

lib/internal/Magento/Framework/Data/Form/Element/Multiselect.php

@@ -57,7 +57,7 @@ public function getElementHtml()
         $this->addClass('select multiselect admin__control-multiselect');
         $html = '';
         if ($this->getCanBeEmpty()) {
-            $html .= '<input type="hidden" name="' . parent::getName() . '" value="" />';
+            $html .= '<input type="hidden" id="' . $this->getHtmlId() . '_hidden" name="' . parent::getName() . '" value="" />';
         }
         if (!empty($this->_data['disabled'])) {
             $html .= '<input type="hidden" name="' . parent::getName() . '_disabled" value="" />';

lib/internal/Magento/Framework/Data/Test/Unit/Form/Element/MultiselectTest.php

@@ -27,10 +27,14 @@ protected function setUp()
     public function testHiddenFieldPresentInMultiSelect()
     {
         $fieldName = 'fieldName';
+        $fieldId = 'fieldId';
         $this->_model->setCanBeEmpty(true);
         $this->_model->setName($fieldName);
+        $this->_model->setId($fieldId);
         $elementHtml = $this->_model->getElementHtml();
-        $this->assertContains('<input type="hidden" name="' . $fieldName . '"', $elementHtml);
+        $this->assertContains(
+            '<input type="hidden" id="' . $fieldId . '_hidden" name="' . $fieldName . '"', $elementHtml
+        );
     }
 
     /**