MC-39128: Cannot delete second layout update in widget

Author: yelahin-serhiy

app/code/Magento/Backend/Block/Widget/Button.php

@@ -5,9 +5,9 @@
  */
 namespace Magento\Backend\Block\Widget;
 
+use Magento\Backend\Block\Template\Context;
 use Magento\Framework\App\ObjectManager;
 use Magento\Framework\Math\Random;
-use Magento\Backend\Block\Template\Context;
 use Magento\Framework\View\Helper\SecureHtmlRenderer;
 
 /**
@@ -125,6 +125,9 @@ protected function _prepareAttributes($title, $classes, $disabled)
             'value' => $this->getValue(),
             'disabled' => $disabled,
         ];
+        if ($this->hasData('onclick_attribute')) {
+            $attributes['onclick'] = $this->getData('onclick_attribute');
+        }
         if ($this->hasData('backend_button_widget_hook_id')) {
             $attributes['backend-button-widget-hook-id'] = $this->getData('backend_button_widget_hook_id');
         }

app/code/Magento/Backend/Test/Unit/Block/Widget/ButtonTest.php

@@ -94,4 +94,16 @@ public function getAttributesHtmlDataProvider()
             ]
         ];
     }
+
+    /**
+     * Verifies ability of adding button onclick attribute
+     *
+     * @return void
+     */
+    public function testOnClickAttribute(): void
+    {
+        $this->_blockMock->setData(['onclick_attribute' => 'value']);
+        $attributes = $this->_blockMock->getAttributesHtml();
+        $this->assertStringContainsString('onclick', $attributes);
+    }
 }

app/code/Magento/Widget/Block/Adminhtml/Widget/Instance/Edit/Tab/Main/Layout.php

@@ -327,7 +327,7 @@ public function getRemoveLayoutButtonHtml()
         )->setData(
             [
                 'label' => $this->escapeHtmlAttr(__('Remove Layout Update')),
-                'onclick' => 'WidgetInstance.removePageGroup(this)',
+                'onclick_attribute' => 'WidgetInstance.removePageGroup(this)',
                 'class' => 'action-delete',
             ]
         );