Issue #2792653 by mglaman, niko-, bmcclure, Dom., xSDx, padma28, gauravjeet, chishah92, rajeshwari10, a.dmitriiev, andypost, steveoliver, markoshust, bojanz, LotharDesmet, nikathone: Checkout coupon pane implementation

Author: mglaman

modules/checkout/src/Plugin/Commerce/CheckoutFlow/CheckoutFlowBase.php

@@ -234,6 +234,11 @@ public function buildForm(array $form, FormStateInterface $form_state, $step_id
     if (empty($step_id)) {
       throw new \InvalidArgumentException('The $step_id cannot be empty.');
     }
+    if ($form_state->isRebuilding()) {
+      // Ensure a fresh order, in case an ajax submit has modified it.
+      $order_storage = $this->entityTypeManager->getStorage('commerce_order');
+      $this->order = $order_storage->load($this->order->id());
+    }
 
     $steps = $this->getVisibleSteps();
     $form['#tree'] = TRUE;

modules/checkout/src/Plugin/Commerce/CheckoutFlow/CheckoutFlowWithPanesBase.php

@@ -533,6 +533,14 @@ public function submitConfigurationForm(array &$form, FormStateInterface $form_s
    */
   public function buildForm(array $form, FormStateInterface $form_state, $step_id = NULL) {
     $form = parent::buildForm($form, $form_state, $step_id);
+    if ($form_state->isRebuilding()) {
+      // The order reference on the panes might be outdated due to
+      // the form cache, so update the order manually once the
+      // parent class reloads it.
+      foreach ($this->panes as $pane_id => $pane) {
+        $this->panes[$pane_id] = $pane->setOrder($this->order);
+      }
+    }
 
     foreach ($this->getVisiblePanes($step_id) as $pane_id => $pane) {
       $form[$pane_id] = [

modules/checkout/src/Plugin/Commerce/CheckoutPane/CheckoutPaneBase.php

@@ -3,6 +3,7 @@
 namespace Drupal\commerce_checkout\Plugin\Commerce\CheckoutPane;
 
 use Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\CheckoutFlowInterface;
+use Drupal\commerce_order\Entity\OrderInterface;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Form\FormStateInterface;
@@ -137,6 +138,14 @@ public function validateConfigurationForm(array &$form, FormStateInterface $form
    */
   public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {}
 
+  /**
+   * {@inheritdoc}
+   */
+  public function setOrder(OrderInterface $order) {
+    $this->order = $order;
+    return $this;
+  }
+
   /**
    * {@inheritdoc}
    */

modules/checkout/src/Plugin/Commerce/CheckoutPane/CheckoutPaneInterface.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\commerce_checkout\Plugin\Commerce\CheckoutPane;
 
+use Drupal\commerce_order\Entity\OrderInterface;
 use Drupal\Component\Plugin\ConfigurablePluginInterface;
 use Drupal\Component\Plugin\DerivativeInspectionInterface;
 use Drupal\Component\Plugin\PluginInspectionInterface;
@@ -15,6 +16,18 @@
  */
 interface CheckoutPaneInterface extends ConfigurablePluginInterface, PluginFormInterface, PluginInspectionInterface, DerivativeInspectionInterface {
 
+  /**
+   * Sets the current order.
+   *
+   * Used to keep the pane order in sync with the checkout flow order.
+   *
+   * @param \Drupal\commerce_order\Entity\OrderInterface $order
+   *   The order.
+   *
+   * @return $this
+   */
+  public function setOrder(OrderInterface $order);
+
   /**
    * Gets the pane ID.
    *

modules/promotion/commerce_promotion.module

@@ -20,6 +20,9 @@ function commerce_promotion_theme() {
     'commerce_promotion_form' => [
       'render element' => 'form',
     ],
+    'commerce_coupon_redemption_form' => [
+      'render element' => 'form',
+    ],
   ];
 }
 

modules/promotion/config/schema/commerce_promotion.schema.yml

@@ -0,0 +1,6 @@
+commerce_checkout.commerce_checkout_pane.coupon_redemption:
+  type: commerce_checkout_pane_configuration
+  mapping:
+    allow_multiple:
+      type: boolean
+      label: 'Allow multiple coupons'