Only attempt to decrement orders after delete

src/Model/Behavior/SequenceBehavior.php

@@ -73,6 +73,13 @@ class SequenceBehavior extends Behavior
         'start' => 1,
     ];
 
+    /**
+     * Old values for the entity being deleted
+     *
+     * @var array|null
+     */
+    protected $_oldValues;
+
     /**
      * Normalize config options.
      *
@@ -235,14 +242,33 @@ public function beforeSave(Event $event, Entity $entity, ArrayObject $options)
      */
     public function beforeDelete(Event $event, Entity $entity)
     {
+        $this->_oldValues = $this->_getOldValues($entity);
+    }
+
+    /**
+     * When you delete a record from a set, you need to decrement the order of all
+     * records that were after it in the set.
+     *
+     * @param \Cake\Event\Event $event The afterDelete event that was fired.
+     * @param \Cake\ORM\Entity $entity The entity that has been deleted.
+     *
+     * @return void
+     */
+    public function afterDelete(Event $event, Entity $entity)
+    {
+        if (!$this->_oldValues) {
+            return;
+        }
+
         $orderField = $this->_config['order'];
-        list($order, $scope) = $this->_getOldValues($entity);
+        list($order, $scope) = $this->_oldValues;
 
         $this->_sync(
             [$orderField => $this->_getUpdateExpression('-')],
             [$orderField . ' >' => $order],
             $scope
         );
+        $this->_oldValues = null;
     }
 
     /**

tests/Fixture/UniqueItemsFixture.php

@@ -0,0 +1,35 @@
+<?php
+namespace ADmad\Sequence\Test\Fixture;
+
+use Cake\TestSuite\Fixture\TestFixture;
+
+class UniqueItemsFixture extends TestFixture
+{
+    /**
+     * fields property.
+     *
+     * @var array
+     */
+    public $fields = [
+        'id' => ['type' => 'integer'],
+        'name' => ['type' => 'string', 'null' => true],
+        'position' => ['type' => 'integer', 'null' => true],
+        '_constraints' => [
+            'primary' => ['type' => 'primary', 'columns' => ['id']],
+            'position' => ['type' => 'unique', 'columns' => ['position']],
+        ],
+    ];
+
+    /**
+     * records property.
+     *
+     * @var array
+     */
+    public $records = [
+        ['name' => 'Item A', 'position' => 0],
+        ['name' => 'Item B', 'position' => 1],
+        ['name' => 'Item C', 'position' => 2],
+        ['name' => 'Item D', 'position' => 3],
+        ['name' => 'Item E', 'position' => 4],
+    ];
+}

tests/TestCase/Model/Behavior/SequenceBehaviorTest.php

@@ -44,12 +44,21 @@ public function initialize(array $config)
     }
 }
 
+class UniqueItems extends Table
+{
+    public function initialize(array $config)
+    {
+        $this->addBehavior('ADmad/Sequence.Sequence', ['start' => 0]);
+    }
+}
+
 class SequenceTest extends TestCase
 {
     public $fixtures = [
         'plugin.ADmad/Sequence.Items',
         'plugin.ADmad/Sequence.GroupedItems',
         'plugin.ADmad/Sequence.KeywordItems',
+        'plugin.ADmad/Sequence.UniqueItems'
     ];
 
     /**
@@ -241,6 +250,16 @@ public function testDelete()
         $this->assertOrder([1, 2, 4, 5], $GroupedItems, ['group_field' => 1]);
         $this->assertOrder([6, 7, 8, 9, 10], $GroupedItems, ['group_field' => 2]);
         $this->assertOrder([11, 12, 13, 14, 15], $GroupedItems, ['group_field' => 3]);
+
+        $UniqueItems = TableRegistry::get('UniqueItems', [
+            'table' => 'unique_items',
+            'alias' => 'UniqueItems',
+            'className' => 'ADmad\Sequence\Test\TestCase\Model\Behavior\UniqueItems',
+        ]);
+
+        $entity = $UniqueItems->get(3);
+        $UniqueItems->delete($entity);
+        $this->assertOrder([1, 2, 4, 5], $UniqueItems);
     }
 
     /**