Adding back button functionality. Fixing a number of bugs.

src/Form/EventSeriesEditForm.php

@@ -25,6 +25,7 @@ class EventSeriesEditForm extends EventSeriesForm {
       /* @var $entity \Drupal\recurring_events\Entity\EventSeries */
       $entity = $this->entity;
 
+      // Determine if there have been changes to the saved eventseries.
       $creation_service = \Drupal::service('recurring_events.event_creation_service');
       $diff_array = $creation_service->buildDiffArray($entity, $form_state);
 
@@ -75,6 +76,7 @@ class EventSeriesEditForm extends EventSeriesForm {
         '#type' => 'submit',
         '#value' => $this->t('Back'),
       ];
+
       $form['actions']['delete']['#printed'] = TRUE;
     }
 
@@ -92,7 +94,18 @@ class EventSeriesEditForm extends EventSeriesForm {
       $form_state->setRebuild();
     }
     else {
-      parent::submitForm($form, $form_state);
+      $triggering_element = $form_state->getTriggeringElement();
+
+      switch ($triggering_element['#id']) {
+        case 'edit-back':
+          $this->step--;
+          $form_state->setRebuild();
+          break;
+
+        case 'edit-submit':
+          parent::submitForm($form, $form_state);
+          break;
+      }
     }
   }
 

src/Plugin/Field/FieldWidget/MonthlyRecurringDateWidget.php

@@ -24,7 +24,7 @@ class MonthlyRecurringDateWidget extends WeeklyRecurringDateWidget {
    */
   public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
     $element = parent::formElement($items, $delta, $element, $form, $form_state);
-
+    $element['#type'] = 'container';
     $element['#states'] = [
       'visible' => [
         ':input[name="recur_type"]' => ['value' => 'monthly'],
@@ -52,7 +52,7 @@ class MonthlyRecurringDateWidget extends WeeklyRecurringDateWidget {
         'fourth' => t('Fourth'),
         'last' => t('Last'),
       ],
-      '#default_value' => $items[$delta]->day_occurrence ? explode(',', $items[$delta]->day_occurrence) : '',
+      '#default_value' => $items[$delta]->day_occurrence ? explode(',', $items[$delta]->day_occurrence) : [],
       '#states' => [
         'visible' => [
           ':input[name="monthly_recurring_date[0][type]"]' => ['value' => 'weekday'],
@@ -66,7 +66,7 @@ class MonthlyRecurringDateWidget extends WeeklyRecurringDateWidget {
       '#type' => 'checkboxes',
       '#title' => t('Days of the Week'),
       '#options' => $days,
-      '#default_value' => $items[$delta]->days ? explode(',', $items[$delta]->days) : '',
+      '#default_value' => $items[$delta]->days ? explode(',', $items[$delta]->days) : [],
       '#states' => [
         'visible' => [
           ':input[name="monthly_recurring_date[0][type]"]' => ['value' => 'weekday'],
@@ -80,7 +80,7 @@ class MonthlyRecurringDateWidget extends WeeklyRecurringDateWidget {
       '#type' => 'checkboxes',
       '#title' => t('Days of the Month'),
       '#options' => $month_days,
-      '#default_value' => $items[$delta]->day_of_month ? explode(',', $items[$delta]->day_of_month) : '',
+      '#default_value' => $items[$delta]->day_of_month ? explode(',', $items[$delta]->day_of_month) : [],
       '#states' => [
         'visible' => [
           ':input[name="monthly_recurring_date[0][type]"]' => ['value' => 'monthday'],

src/Plugin/Field/FieldWidget/WeeklyRecurringDateWidget.php

@@ -26,6 +26,7 @@ class WeeklyRecurringDateWidget extends DateRangeDefaultWidget {
   public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
     $element = parent::formElement($items, $delta, $element, $form, $form_state);
 
+    $element['#type'] = 'container';
     $element['#states'] = [
       'visible' => [
         ':input[name="recur_type"]' => ['value' => 'weekly'],
@@ -69,7 +70,7 @@ class WeeklyRecurringDateWidget extends DateRangeDefaultWidget {
       '#type' => 'checkboxes',
       '#title' => t('Days of the Week'),
       '#options' => $days,
-      '#default_value' => $items[$delta]->days ? explode(',', $items[$delta]->days) : '',
+      '#default_value' => $items[$delta]->days ? explode(',', $items[$delta]->days) : [],
       '#weight' => 5,
     ];