Issue #2998215 by tim.plunkett, Ronak.addweb, bkosborne: PHP notices/warnings...

Issue #2998215 by tim.plunkett, Ronak.addweb, bkosborne: PHP notices/warnings when managing display for non-default view mode when LB is enabled w/ overrides

core/modules/layout_builder/src/Form/LayoutBuilderEntityViewDisplayForm.php

@@ -47,6 +47,10 @@ public function buildForm(array $form, FormStateInterface $form_state, SectionSt
   public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
 
+    // Remove the Layout Builder field from the list.
+    $form['#fields'] = array_diff($form['#fields'], ['layout_builder__layout']);
+    unset($form['fields']['layout_builder__layout']);
+
     $is_enabled = $this->entity->isLayoutBuilderEnabled();
     if ($is_enabled) {
       // Hide the table of fields.
@@ -54,10 +58,6 @@ public function form(array $form, FormStateInterface $form_state) {
       $form['#fields'] = [];
       $form['#extra'] = [];
     }
-    else {
-      // Remove the Layout Builder field from the list.
-      $form['#fields'] = array_diff($form['#fields'], ['layout_builder__layout']);
-    }
 
     $form['manage_layout'] = [
       '#type' => 'link',
@@ -180,7 +180,7 @@ public function entityFormEntityBuild($entity_type_id, LayoutEntityDisplayInterf
    * {@inheritdoc}
    */
   protected function buildFieldRow(FieldDefinitionInterface $field_definition, array $form, FormStateInterface $form_state) {
-    if ($this->entity->isLayoutBuilderEnabled() || $field_definition->getType() === 'layout_section') {
+    if ($this->entity->isLayoutBuilderEnabled()) {
       return [];
     }
 

core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php

@@ -225,6 +225,33 @@ public function testLayoutBuilderUi() {
     $assert_session->elementNotExists('css', '.field--name-field-my-text');
   }
 
+  /**
+   * Tests that a non-default view mode works as expected.
+   */
+  public function testNonDefaultViewMode() {
+    $assert_session = $this->assertSession();
+    $page = $this->getSession()->getPage();
+
+    $this->drupalLogin($this->drupalCreateUser([
+      'configure any layout',
+      'administer node display',
+    ]));
+
+    $field_ui_prefix = 'admin/structure/types/manage/bundle_with_section_field';
+    // Allow overrides for the layout.
+    $this->drupalGet("$field_ui_prefix/display/default");
+    $page->checkField('layout[enabled]');
+    $page->pressButton('Save');
+    $page->checkField('layout[allow_custom]');
+    $page->pressButton('Save');
+
+    $this->clickLink('Teaser');
+    // Enabling Layout Builder for the default mode does not affect the teaser.
+    $assert_session->addressEquals("$field_ui_prefix/display/teaser");
+    $assert_session->elementNotExists('css', '#layout-builder__layout');
+    $assert_session->checkboxNotChecked('layout[enabled]');
+  }
+
   /**
    * Tests that component's dependencies are respected during removal.
    */