Issue #3094366 by mohit_aghera, KittenDestroyer, Berdir, rensingh99: Error when saving config entity with "Link to entity" checked if field formatters

core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/StringFormatter.php

@@ -92,14 +92,15 @@ class StringFormatter extends FormatterBase {
    */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form = parent::settingsForm($form, $form_state);
-
     $entity_type = $this->entityTypeManager->getDefinition($this->fieldDefinition->getTargetEntityTypeId());
 
+    if ($entity_type->hasLinkTemplate('canonical')) {
       $form['link_to_entity'] = [
         '#type' => 'checkbox',
         '#title' => $this->t('Link to the @entity_label', ['@entity_label' => $entity_type->getLabel()]),
         '#default_value' => $this->getSetting('link_to_entity'),
       ];
+    }
 
     return $form;
   }
@@ -111,8 +112,10 @@ class StringFormatter extends FormatterBase {
     $summary = [];
     if ($this->getSetting('link_to_entity')) {
       $entity_type = $this->entityTypeManager->getDefinition($this->fieldDefinition->getTargetEntityTypeId());
+      if ($entity_type->hasLinkTemplate('canonical')) {
         $summary[] = $this->t('Linked to the @entity_label', ['@entity_label' => $entity_type->getLabel()]);
       }
+    }
     return $summary;
   }
 
@@ -122,8 +125,11 @@ class StringFormatter extends FormatterBase {
   public function viewElements(FieldItemListInterface $items, $langcode) {
     $elements = [];
     $url = NULL;
-    if ($this->getSetting('link_to_entity')) {
+    $entity = $items->getEntity();
-      $url = $this->getEntityUrl($items->getEntity());
+    $entity_type = $entity->getEntityType();
+
+    if ($this->getSetting('link_to_entity') && !$entity->isNew() && $entity_type->hasLinkTemplate('canonical')) {
+      $url = $this->getEntityUrl($entity);
     }
 
     foreach ($items as $delta => $item) {

core/modules/field/tests/src/Kernel/String/StringFormatterTest.php

@@ -5,6 +5,7 @@ namespace Drupal\Tests\field\Kernel\String;
 use Drupal\Component\Utility\Html;
 use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
 use Drupal\Core\Entity\FieldableEntityInterface;
+use Drupal\entity_test\Entity\EntityTestLabel;
 use Drupal\entity_test\Entity\EntityTestRev;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
@@ -67,6 +68,7 @@ class StringFormatterTest extends KernelTestBase {
     // Configure the theme system.
     $this->installConfig(['system', 'field']);
     $this->installEntitySchema('entity_test_rev');
+    $this->installEntitySchema('entity_test_label');
 
     $this->entityType = 'entity_test_rev';
     $this->bundle = $this->entityType;
@@ -185,4 +187,46 @@ class StringFormatterTest extends KernelTestBase {
     $this->assertLinkByHref($entity->toUrl('canonical')->toString());
   }
 
+  /**
+   * Test "link_to_entity" feature on fields which are added to config entity.
+   */
+  public function testLinkToContentForEntitiesWithNoCanonicalPath() {
+    $this->enableModules(['entity_test']);
+    $field_name = 'test_field_name';
+    $entity_type = $bundle = 'entity_test_label';
+
+    $field_storage = FieldStorageConfig::create([
+      'field_name' => $field_name,
+      'entity_type' => $entity_type,
+      'type' => 'string',
+    ]);
+    $field_storage->save();
+
+    $instance = FieldConfig::create([
+      'field_storage' => $field_storage,
+      'bundle' => $entity_type,
+      'label' => $this->randomMachineName(),
+    ]);
+    $instance->save();
+
+    $display = \Drupal::service('entity_display.repository')
+      ->getViewDisplay($entity_type, $bundle)
+      ->setComponent($field_name, [
+        'type' => 'string',
+        'settings' => [
+          'link_to_entity' => TRUE,
+        ],
+        'region' => 'content',
+      ]);
+    $display->save();
+
+    $value = $this->randomMachineName();
+    $entity = EntityTestLabel::create(['name' => 'test']);
+    $entity->{$field_name}->value = $value;
+    $entity->save();
+
+    $this->renderEntityFields($entity, $display);
+    $this->assertRaw($value);
+  }
+
 }