Merge pull request #63 from systopia/date-use-null-if-not-set

Date field: Use default or `NULL` if not set

src/Form/Control/Callbacks/DateValueCallback.php

@@ -0,0 +1,51 @@
+<?php
+
+/*
+ * Copyright (C) 2022 SYSTOPIA GmbH
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace Drupal\json_forms\Form\Control\Callbacks;
+
+use Drupal\Core\Form\FormStateInterface;
+
+final class DateValueCallback {
+
+  /**
+   * @param array<int|string, mixed> $element
+   * @param mixed $input
+   * @param \Drupal\Core\Form\FormStateInterface $formState
+   *
+   * @return mixed
+   */
+  public static function convert(array $element, $input, FormStateInterface $formState) {
+    if (FALSE === $input || '' === $input) {
+      $value = $element['#default_value'] ?? NULL;
+
+      if (NULL === $value) {
+        // Prevent empty string as value. Drupal sets an empty string in this
+        // case if no value is set in the form state.
+        $formState->setValueForElement($element, NULL);
+      }
+
+      return $value;
+    }
+
+    return $input;
+  }
+
+}

src/Form/Control/DateArrayFactory.php

@@ -24,6 +24,7 @@
 use Assert\Assertion;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\json_forms\Form\AbstractConcreteFormArrayFactory;
+use Drupal\json_forms\Form\Control\Callbacks\DateValueCallback;
 use Drupal\json_forms\Form\Control\Util\BasicFormPropertiesFactory;
 use Drupal\json_forms\Form\FormArrayFactoryInterface;
 use Drupal\json_forms\JsonForms\Definition\Control\ControlDefinition;
@@ -47,6 +48,7 @@ public function createFormArray(
     /** @var \Drupal\json_forms\JsonForms\Definition\Control\ControlDefinition $definition */
     $form = [
       '#type' => 'date',
+      '#value_callback' => DateValueCallback::class . '::convert',
     ] + BasicFormPropertiesFactory::createFieldProperties($definition, $formState);
 
     // @phpstan-ignore-next-line