Issue #3311372 by jurgenhaas, the_g_bomb: Make date format configurable

config/install/diff.settings.yml

 general_settings:
   radio_behavior: simple
+  date_format: short
   context_lines_leading: 1
   context_lines_trailing: 1
   revision_pager_limit: 50

src/DiffLayoutBase.php

@@ -70,7 +70,7 @@ abstract class DiffLayoutBase extends PluginBase implements DiffLayoutInterface,
    */
   protected function buildRevisionLink(ContentEntityInterface $revision): GeneratedLink {
     if ($revision instanceof RevisionLogInterface) {
-      $revision_date = $this->date->format($revision->getRevisionCreationTime(), 'short');
+      $revision_date = $this->date->format($revision->getRevisionCreationTime(), $this->configFactory->get('diff.settings')->get('general_settings.date_format') ?? 'short');
       return Link::fromTextAndUrl($revision_date, $revision->toUrl('revision'))->toString();
     }
     return Link::fromTextAndUrl($revision->label(), $revision->toUrl('revision'))->toString();
@@ -130,7 +130,7 @@ abstract class DiffLayoutBase extends PluginBase implements DiffLayoutInterface,
 
       $revision_link['date'] = [
         '#type' => 'link',
-        '#title' => $this->date->format($revision->getRevisionCreationTime(), 'short'),
+        '#title' => $this->date->format($revision->getRevisionCreationTime(), $this->configFactory->get('diff.settings')->get('general_settings.date_format') ?? 'short'),
         '#url' => $revision->toUrl('revision'),
         '#prefix' => '<div class="diff-revision__item diff-revision__item-date">',
         '#suffix' => '</div>',

src/Form/GeneralSettingsForm.php

@@ -73,6 +73,17 @@ class GeneralSettingsForm extends ConfigFormBase {
       '#description' => $this->t('<em>Simple exclusion</em> means that users will not be able to select the same revision, <em>Linear restrictions</em> means that users can only select older or newer revisions of the current selections.'),
     ];
 
+    $date_formats = [];
+    foreach (\Drupal::entityTypeManager()->getStorage('date_format')->loadMultiple() as $machine_name => $value) {
+      $date_formats[$machine_name] = $value->label();
+    }
+    $form['date_format'] = array(
+      '#type' => 'select',
+      '#title' => $this->t('Date format'),
+      '#default_value' => $config->get('general_settings.date_format'),
+      '#options' => $date_formats,
+    );
+
     $layout_plugins = $this->diffLayoutManager->getDefinitions();
     $weight = \count($layout_plugins) + 1;
     $layout_plugins_order = [];
@@ -235,6 +246,7 @@ class GeneralSettingsForm extends ConfigFormBase {
 
     $keys = [
       'radio_behavior',
+      'date_format',
       'context_lines_leading',
       'context_lines_trailing',
       'layout_plugins',

src/Form/RevisionOverviewForm.php

@@ -155,7 +155,7 @@ class RevisionOverviewForm extends FormBase {
             '#theme' => 'username',
             '#account' => $revision->getRevisionUser(),
           ];
-          $revision_date = $this->date->format($revision->getRevisionCreationTime(), 'short');
+          $revision_date = $this->date->format($revision->getRevisionCreationTime(), $this->configFactory->get('diff.settings')->get('general_settings.date_format') ?? 'short');
           // Use revision link to link to revisions that are not active.
           if ($vid != $node->getRevisionId()) {
             $link = Link::fromTextAndUrl($revision_date, new Url('entity.node.revision', ['node' => $node->id(), 'node_revision' => $vid]));

src/Plugin/diff/Field/DateFieldBuilder.php

+<?php
+
+namespace Drupal\diff\Plugin\diff\Field;
+
+use Drupal\Core\Datetime\DateFormatter;
+use Drupal\diff\FieldDiffBuilderBase;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Plugin to compare date fields.
+ *
+ * @FieldDiffBuilder(
+ *   id = "date_field_diff_builder",
+ *   label = @Translation("Date Field Diff"),
+ *   field_types = {
+ *     "changed",
+ *     "created",
+ *     "datetime",
+ *     "daterange",
+ *     "timestamp"
+ *   },
+ * )
+ */
+class DateFieldBuilder extends FieldDiffBuilderBase {
+
+    /**
+     * The date formatter service.
+     *
+     * @var \Drupal\Core\Datetime\DateFormatter
+     */
+    protected DateFormatter $date;
+
+    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+        /** @var \Drupal\diff\Plugin\diff\Field\DateFieldBuilder $instance */
+        $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
+        $instance->date = $container->get('date.formatter');
+        return $instance;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function build(FieldItemListInterface $field_items) {
+        $result = array();
+
+        // Every item from $field_items is of type FieldItemInterface.
+        foreach ($field_items as $field_key => $field_item) {
+            if (!$field_item->isEmpty()) {
+                foreach ($field_item->getValue() as $value) {
+                    if (!is_numeric($value)) {
+                        $value = (new \DateTime($value))->getTimestamp();
+                    }
+                    $result[$field_key][] = $this->date->format((int) $value, $this->configuration['format']);
+                }
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+        $date_formats = [];
+        foreach (\Drupal::entityTypeManager()->getStorage('date_format')->loadMultiple() as $machine_name => $value) {
+            $date_formats[$machine_name] = $value->label();
+        }
+        $form['format'] = array(
+            '#type' => 'select',
+            '#title' => $this->t('Format'),
+            '#default_value' => $this->configuration['format'],
+            '#options' => $date_formats,
+        );
+
+        return parent::buildConfigurationForm($form, $form_state);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+        $this->configuration['format'] = $form_state->getValue('format');
+
+        parent::submitConfigurationForm($form, $form_state);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function defaultConfiguration() {
+        $default_configuration = array(
+            'format' => 'short',
+        );
+        $default_configuration += parent::defaultConfiguration();
+
+        return $default_configuration;
+    }
+
+}