Ensure calculated values are set on initial load

Author: Dominic Tubach

js/initial-calculation.js

@@ -0,0 +1,31 @@
+/*
+ * 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/>.
+ */
+
+/**
+ * Performs a calculation when a form is initially loaded.
+ */
+(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) => {
+        // Trigger a "change" event which results in an AJAX call that performs the calculations.
+        element.dispatchEvent(new Event('change'));
+      });
+    }
+  };
+
+})(Drupal, once);

json_forms.libraries.yml

@@ -16,6 +16,14 @@ disable_buttons_on_ajax:
   dependencies:
     - core/jquery
 
+initial_calculation:
+  version: 0.1.0
+  js:
+    js/initial-calculation.js: {}
+  dependencies:
+    - core/drupal
+    - core/once
+
 number_input:
   version: 0.1.0
   js:

src/Form/AbstractJsonFormsForm.php

@@ -130,6 +130,17 @@ protected function buildJsonFormsForm(
     $form['#attached']['library'][] = 'json_forms/disable_buttons_on_ajax';
     $form['#attached']['library'][] = 'json_forms/vertical_tabs';
 
+    if (!$formState->isCached()) {
+      if (TRUE === $formState->get('$calculateUsed')) {
+        $form['#attached']['library'][] = 'json_forms/initial_calculation';
+      }
+
+      // Drupal prevents caching on safe methods.
+      if (!$this->getRequest()->isMethodSafe()) {
+        $formState->setCached();
+      }
+    }
+
     return $form;
   }
 

src/Form/Control/SubmitButtonArrayFactory.php

@@ -63,8 +63,9 @@ public function createFormArray(
       // Override value set in BasicFormPropertiesFactory.
       '#limit_validation_errors' => NULL,
       '#_data' => $definition->getOptionsValue('data'),
-      '#attributes' => ['class' => ['json-forms-submit']],
     ] + BasicFormPropertiesFactory::createFieldProperties($definition, $formState);
+    // @phpstan-ignore-next-line
+    $form['#attributes']['class'][] = 'json-forms-submit';
 
     if (NULL !== $definition->getOptionsValue('confirm')) {
       // @phpstan-ignore-next-line

src/Form/Control/Util/BasicFormPropertiesFactory.php

@@ -83,6 +83,16 @@ public static function createFieldProperties(ControlDefinition $definition, Form
       '#_nullable' => $definition->isNullable(),
     ];
 
+    $calcInitField = FALSE;
+    if ($definition->isCalculated()) {
+      $formState->set('$calculateUsed', TRUE);
+    }
+    elseif (!$formState->has('$hasCalcInitField')) {
+      $formState->set('$hasCalcInitField', TRUE);
+      $form['#attributes']['data-json-forms-init-calculation'] = '1';
+      $calcInitField = TRUE;
+    }
+
     $readOnlyValuePath = array_merge(['readOnlyValues'], $definition->getPropertyPath());
     if ((!$formState->isCached() || $definition->isReadOnly())
       && $formState->hasTemporaryValue($definition->getPropertyPath())
@@ -112,7 +122,7 @@ public static function createFieldProperties(ControlDefinition $definition, Form
       $form['#value'] = $definition->getConst();
     }
 
-    if (!$form['#disabled'] && TRUE === $formState->get('recalculateOnChange')) {
+    if ((!$form['#disabled'] && TRUE === $formState->get('recalculateOnChange')) || $calcInitField) {
       $form['#ajax'] = [
         'callback' => RecalculateCallback::class . '::onChange',
         'event' => 'change',