Issue #2915175 by vaplas, Phonoman, Lendude: Duplicating a Page to Block after...

Issue #2915175 by vaplas, Phonoman, Lendude: Duplicating a Page to Block after changing the display id and then saving the view destroys the Page

core/modules/views/src/Entity/View.php

@@ -245,6 +245,7 @@ public function duplicateDisplayAsType($old_display_id, $new_display_type) {
     $display_duplicate = $displays[$old_display_id];
     unset($display_duplicate['display_title']);
     unset($display_duplicate['display_plugin']);
+    unset($display_duplicate['new_id']);
 
     $displays[$new_display_id] = NestedArray::mergeDeep($displays[$new_display_id], $display_duplicate);
     $displays[$new_display_id]['id'] = $new_display_id;

core/modules/views_ui/tests/src/Functional/DisplayCRUDTest.php

@@ -143,6 +143,16 @@ public function testDuplicateDisplay() {
     $this->assertFalse(isset($block_1->display['display_options']['path']));
     $this->assertEqual($block_1->getOption('title'), $random_title, 'The overridden title option from the display got copied into the duplicate');
     $this->assertEqual($block_1->getOption('css_class'), $random_css, 'The overridden css_class option from the display got copied into the duplicate');
+
+    // Test duplicating a display after changing the machine name.
+    $view_id = $view->id();
+    $this->drupalPostForm("admin/structure/views/nojs/display/$view_id/page_2/display_id", ['display_id' => 'page_new'], 'Apply');
+    $this->drupalPostForm(NULL, [], 'Duplicate as Block');
+    $this->drupalPostForm(NULL, [], t('Save'));
+    $view = Views::getView($view_id);
+    $view->initDisplay();
+    $this->assertNotNull($view->displayHandlers->get('page_new'), 'The original display is saved with a changed id');
+    $this->assertNotNull($view->displayHandlers->get('block_2'), 'The duplicate display is saved with new id');
   }
 
 }