Initial calculation with disabled element

Author: Dominic Tubach

js/initial-calculation.js

@@ -18,14 +18,22 @@
 /**
  * Performs a calculation when a form is initially loaded.
  */
-(function (Drupal, once) {
+(function (Drupal, once, $) {
   Drupal.behaviors.json_forms_initial_calculation = {
     attach: function (context, settings) {
       once('json-forms-initial-calculation', '[data-json-forms-init-calculation="1"]', context).forEach((element) => {
+        if (element.disabled) {
+          // Drupal enables the element after the AJAX call so we have to disable it again.
+          const handler = function (event) {
+            element.disabled = true;
+            $(document).off('ajaxStop', handler);
+          };
+          $(document).on('ajaxStop', handler);
+        }
         // Trigger a "change" event which results in an AJAX call that performs the calculations.
         element.dispatchEvent(new Event('change'));
       });
     }
   };
 
-})(Drupal, once);
+})(Drupal, once, jQuery);

json_forms.libraries.yml

@@ -17,7 +17,7 @@ disable_buttons_on_ajax:
     - core/jquery
 
 initial_calculation:
-  version: 0.1.0
+  version: 0.1.1
   js:
     js/initial-calculation.js: {}
   dependencies:

src/Form/Control/Callbacks/TriggeringElementCallback.php

@@ -0,0 +1,71 @@
+<?php
+
+/*
+ * Copyright (C) 2025 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 TriggeringElementCallback {
+
+  /**
+   * @param array<int|string, mixed> $element
+   *
+   * @return array<int|string, mixed>
+   */
+  public static function onAfterBuild(array $element, FormStateInterface $formState): array {
+    // For disabled elements the triggering element is not set. (Required if
+    // disabled element is used for the initial calculation call.)
+    if (NULL === $formState->getTriggeringElement() && self::elementTriggeredScriptedSubmission($element, $formState)) {
+      $formState->setTriggeringElement($element);
+    }
+
+    return $element;
+  }
+
+  /**
+   * Based on
+   * \Drupal\Core\Form\FormBuilder::elementTriggeredScriptedSubmission().
+   *
+   * Detects if an element triggered the form submission via Ajax.
+   *
+   * This detects button or non-button controls that trigger a form submission
+   * via Ajax or some other scriptable environment. These environments can set
+   * the special input key '_triggering_element_name' to identify the triggering
+   * element. If the name alone doesn't identify the element uniquely, the input
+   * key '_triggering_element_value' may also be set to require a match on
+   * element value. An example where this is needed is if there are several
+   * // buttons all named 'op', and only differing in their value.
+   *
+   * @param array<int|string, mixed> $element
+   */
+  private static function elementTriggeredScriptedSubmission(array $element, FormStateInterface $formState): bool {
+    $input = $formState->getUserInput();
+    if ($element['#name'] === ($input['_triggering_element_name'] ?? NULL)) {
+      // @phpstan-ignore equal.notAllowed
+      if (!isset($input['_triggering_element_value']) || $input['_triggering_element_value'] == $element['#value']) {
+        return TRUE;
+      }
+    }
+
+    return FALSE;
+  }
+
+}

src/Form/Control/Util/BasicFormPropertiesFactory.php

@@ -23,6 +23,7 @@
 
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\json_forms\Form\Control\Callbacks\RecalculateCallback;
+use Drupal\json_forms\Form\Control\Callbacks\TriggeringElementCallback;
 use Drupal\json_forms\Form\Control\Rule\StatesArrayFactory;
 use Drupal\json_forms\Form\Util\DescriptionDisplayUtil;
 use Drupal\json_forms\JsonForms\Definition\Control\ControlDefinition;
@@ -138,6 +139,11 @@ public static function createFieldProperties(ControlDefinition $definition, Form
         'progress' => [],
         'disable-refocus' => TRUE,
       ];
+      if ($calcInitField && $form['#disabled']) {
+        $form['#after_build'] = [
+          [TriggeringElementCallback::class, 'onAfterBuild'],
+        ];
+      }
     }
 
     $form += static::createBasicProperties($definition);