Fix statistical design issue when uploading files to the design entity …

…#616

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Fix managed permissions to edit taxonomy terms. [#622](https://github.com/Rothamsted-Ecoinformatics/farm_rothamsted/issues/622)
+- Fix statistical design issue when uploading files to design entity. [#616](https://github.com/Rothamsted-Ecoinformatics/farm_rothamsted/issues/616)
 
 ## [2.18.0](https://github.com/Rothamsted-Ecoinformatics/farm_rothamsted/milestone/39) 2023-12-11
 

modules/farm_rothamsted_experiment_research/src/Form/DesignEntityForm.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\farm_rothamsted_experiment_research\Form;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Form\FormStateInterface;
 
 /**
@@ -283,17 +284,29 @@ public function form(array $form, FormStateInterface $form_state) {
       ];
     }
 
-    // Add ajax.
+    // Add ajax to update the statistical design field after changing the
+    // selected blocking structure.
     $form['statistical_design']['#attributes']['id'] = 'statistical-design-wrapper';
     $form['blocking_structure']['widget']['#ajax'] = [
       'callback' => [$this, 'blockingStructureCallback'],
       'wrapper' => 'statistical-design-wrapper',
       'event' => 'change',
     ];
 
-    // Build options.
+    // Build options from the selected blocking structure.
+    // Check if a value has been set to the form state storage (not form state
+    // values) via AJAX before using entity's current field value.
+    // This prevents errors from happening when other elements reset the form
+    // state, like file uploads. See issue #616.
+    $blocking_structure = $form_state->get('blocking_structure') ?? $this->entity->get('blocking_structure')->value;
+    if (($trigger = $form_state->getTriggeringElement()) && NestedArray::getValue($trigger['#array_parents'], [0]) == 'blocking_structure') {
+      $blocking_structure = $trigger['#value'];
+    }
+    // Save the blocking structure to form state storage.
+    $form_state->set('blocking_structure', $blocking_structure);
+
+    // Load the statistical design options.
     $options = [];
-    $blocking_structure = $form_state->getValue(['blocking_structure', 0, 'value']) ?? $this->entity->get('blocking_structure')->value;
     if ($blocking_structure) {
       $options = farm_rothamsted_experiment_research_statistical_design_options($blocking_structure);
     }