Fixed #620

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Added `craft\commerce\test\fixtures\elements\ProductFixture`. ([#1009](https://github.com/craftcms/commerce/pull/1009))
 - Added “Customer Info” tab to Edit User page, its appearance can be controlled with `showCustomerTabOnEditUser` Commerce setting.
 - Added the `activeCartDuration` setting to determine if a cart should show as inactive on the Order index page. ([#959](https://github.com/craftcms/commerce/issues/959))
+- Added the `allowEmptyCartOnCheckout` setting to determine if a customer can check out with an empty cart. ([#620](https://github.com/craftcms/commerce/issues/620))
 - Added `getActiveCarts` and `getInactiveCarts` to the customer model.
 - Added the ability to delete customer addresses from the customer info tab on the Edit User page. ([#171](https://github.com/craftcms/commerce/issues/171))
 

src/controllers/PaymentsController.php

@@ -9,6 +9,7 @@
 
 use Craft;
 use craft\commerce\base\Gateway;
+use craft\commerce\elements\Order;
 use craft\commerce\errors\CurrencyException;
 use craft\commerce\errors\PaymentException;
 use craft\commerce\errors\PaymentSourceException;
@@ -53,13 +54,13 @@ public function actionPay()
         $this->requirePostRequest();
 
         $customError = '';
-        $order = null;
 
         $plugin = Plugin::getInstance();
         $request = Craft::$app->getRequest();
         $session = Craft::$app->getSession();
 
         if (($number = $request->getBodyParam('orderNumber')) !== null) {
+            /** @var Order $order */
             $order = $plugin->getOrders()->getOrderByNumber($number);
 
             if (!$order) {
@@ -73,10 +74,8 @@ public function actionPay()
 
                 return null;
             }
-        }
-
-        // Get the cart if no order number was passed.
-        if (!$order) {
+        } else {
+            /** @var Order $order */
             $order = $plugin->getCarts()->getCart(true);
         }
 
@@ -120,6 +119,18 @@ public function actionPay()
             return null;
         }
 
+        if (!$plugin->getSettings()->allowEmptyCartOnCheckout && $order->getIsEmpty()) {
+            $error = Craft::t('commerce', 'Order can not be empty.');
+
+            if ($request->getAcceptsJson()) {
+                return $this->asErrorJson($error);
+            }
+
+            $session->setError($error);
+
+            return null;
+        }
+
         // Set if the customer should be registered on order completion
         if ($request->getBodyParam('registerUserOnOrderComplete')) {
             $order->registerUserOnOrderComplete = true;

src/models/Settings.php

@@ -162,6 +162,12 @@ class Settings extends Model
      */
     public $autoSetNewCartAddresses = true;
 
+    /**
+     * @var bool Allow the cart to be empty on checkout
+     * @todo Set this to false in 3.0
+     */
+    public $allowEmptyCartOnCheckout = true;
+
     /**
      * @var bool
      */