From 0e7b21c0d86fbed9e8f64ed8bfb66a342407b4d9 Mon Sep 17 00:00:00 2001
From: Walther Lalk <dakota@users.noreply.github.com>
Date: Thu, 23 Apr 2020 09:57:36 +0200
Subject: [PATCH] Fix issue with single entity when ResultSetDecorators are
 used

---
 src/Listener/JsonApiListener.php                |  2 +-
 tests/TestCase/Listener/JsonApiListenerTest.php | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/Listener/JsonApiListener.php b/src/Listener/JsonApiListener.php
index 85e1936f..30c2b5c3 100644
--- a/src/Listener/JsonApiListener.php
+++ b/src/Listener/JsonApiListener.php
@@ -874,7 +874,7 @@ protected function _getSingleEntity(Subject $subject): ?EntityInterface
             return (clone $subject->entities)->first();
         }
 
-        if (!empty($subject->entities) && $subject->entities instanceof ResultSet) {
+        if (!empty($subject->entities) && $subject->entities instanceof ResultSetInterface) {
             if ($subject->entities->first() === null) {
                 $repository = $subject->query->getRepository();
                 $entity = $repository->getEntityClass();
diff --git a/tests/TestCase/Listener/JsonApiListenerTest.php b/tests/TestCase/Listener/JsonApiListenerTest.php
index e4ad80cc..71bd70db 100644
--- a/tests/TestCase/Listener/JsonApiListenerTest.php
+++ b/tests/TestCase/Listener/JsonApiListenerTest.php
@@ -5,6 +5,7 @@
 
 use Cake\Controller\Controller;
 use Cake\Core\Plugin;
+use Cake\Datasource\ResultSetDecorator;
 use Cake\Event\Event;
 use Cake\Filesystem\File;
 use Cake\Http\Exception\BadRequestException;
@@ -848,6 +849,18 @@ public function testGetSingleEntity()
         $result = $this->callProtectedMethod('_getSingleEntity', [$subject], $listener);
         $this->assertSame($entity, $result);
 
+        $subject->entities = $this->getMockBuilder(ResultSetDecorator::class)
+            ->disableOriginalConstructor()
+            ->onlyMethods(['first'])
+            ->getMock();
+
+        $subject->entities->method('first')
+            ->willReturn($entity);
+
+        $this->setReflectionClassInstance($listener);
+        $result = $this->callProtectedMethod('_getSingleEntity', [$subject], $listener);
+        $this->assertSame($entity, $result);
+
         unset($subject->entities);
 
         $subject->entity = $entity;