Some fixes.

lib/CollectionTraversal/CollectionTraversalStrategyInterface.php

@@ -7,15 +7,15 @@
 interface CollectionTraversalStrategyInterface
 {
     /**
-     * @param $propertyValue
+     * @param mixed $propertyValue
      *
      * @return bool
      */
     public function supports($propertyValue): bool;
 
     /**
      * @param ObjectCollectionInterface $objectCollection
-     * @param $propertyValue
+     * @param mixed $propertyValue
      */
     public function traverse(ObjectCollectionInterface $objectCollection, $propertyValue);
 }

lib/Facade.php

@@ -19,7 +19,7 @@
 class Facade
 {
     /**
-     * @var EntityManagerInterface
+     * @var EntityManagerInterface|null
      */
     protected $entityManager;
 
@@ -111,12 +111,14 @@ public function getBufferedDoctrineOrmCollector(): BufferedCollectorInterface
 
     /**
      * @return MetadataWrapperProvider
+     *
+     * @throws \Exception
      */
     protected function getMetadataWrapperProvider(): MetadataWrapperProvider
     {
-        $this->assertEntityManagerAvailable();
+        $entityManager = $this->getEntityManager();
         if (!$this->metadataWrapperProvider instanceof MetadataWrapperProvider) {
-            $this->metadataWrapperProvider = new MetadataWrapperProvider($this->entityManager);
+            $this->metadataWrapperProvider = new MetadataWrapperProvider($entityManager);
         }
 
         return $this->metadataWrapperProvider;
@@ -190,4 +192,18 @@ protected function assertEntityManagerAvailable()
             throw new \Exception('Entity manager not available.');
         }
     }
+
+    /**
+     * @return EntityManagerInterface
+     *
+     * @throws \Exception
+     */
+    protected function getEntityManager(): EntityManagerInterface
+    {
+        if (!$this->entityManager instanceof EntityManagerInterface) {
+            throw new \Exception('Entity manager not available.');
+        }
+
+        return $this->entityManager;
+    }
 }

lib/Loader/DoctrineOrmEntityLoader.php

@@ -33,7 +33,7 @@ class DoctrineOrmEntityLoader
     protected $nonProxiedAssociationQueryExecutor;
 
     /**
-     * @var int
+     * @var int|null
      */
     protected $chunkSize = 1000;
 
@@ -132,12 +132,13 @@ public function loadAssociatedUninitializedCollectionsAndProxies(
             return;
         }
 
-        // Or we can have one-to-one association with source being the inverse side.
+        // Or we have one-to-one association with source being the inverse side.
         if (
             $associationMetadataWrapper->isOneToOne()
             && $associationMetadataWrapper->isInverseSide()
         ) {
-            // We don't have to do anything as these objects as automatically loaded by Doctrine.
+            // We don't have to do anything as these objects are automatically loaded by Doctrine with separate queries
+            // and there's no way to optimize this.
 
             return;
         }

lib/Metadata/ClassMetadataWrapper.php

@@ -25,7 +25,7 @@ class ClassMetadataWrapper
     protected $classMetadata;
 
     /**
-     * @var string
+     * @var string|null
      */
     protected $identifierFieldName;
 
@@ -116,7 +116,7 @@ public function getAssociationMetadataWrapper(string $associationName)
                 $associationMapping = $this->classMetadata->getAssociationMapping($associationName);
             } catch (MappingException $e) {
                 if (0 === strpos($e->getMessage(), 'No mapping found for field ')) {
-                    return;
+                    return null;
                 }
                 throw $e;
             }

lib/Metadata/MetadataWrapperProvider.php

@@ -3,6 +3,7 @@
 namespace Xsolve\Associate\Metadata;
 
 use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\EntityRepository;
 use Doctrine\ORM\Mapping\ClassMetadata;
 
 class MetadataWrapperProvider
@@ -13,7 +14,7 @@ class MetadataWrapperProvider
     protected $entityManager;
 
     /**
-     * @var ClassMetadataWrapper[]
+     * @var (ClassMetadataWrapper|null)[]
      */
     protected $classMetadataWrappers = [];
 
@@ -44,7 +45,7 @@ function (string $className) { return $this->getClassMetadataWrapperByClassName(
 
         // If metadata were not available for some objects.
         if (in_array(null, $classMetadataWrappers, true)) {
-            return;
+            return null;
         }
 
         $classNames = array_unique(array_map(
@@ -76,18 +77,20 @@ function (ClassMetadataWrapper $classMetadataWrapper) {
      * @param string $className
      *
      * @return ClassMetadataWrapper|null
+     *
+     * @throws \Exception
      */
     public function getClassMetadataWrapperByClassName(string $className)
     {
         if (!array_key_exists($className, $this->classMetadataWrappers)) {
             $classMetadata = $this->entityManager->getClassMetadata($className);
 
             if ($classMetadata instanceof ClassMetadata) {
-                $this->classMetadataWrappers[$className] = new ClassMetadataWrapper(
-                    $this,
-                    $this->entityManager->getRepository($className),
-                    $classMetadata
-                );
+                $entityRepository = $this->entityManager->getRepository($className);
+                if (!$entityRepository instanceof EntityRepository) {
+                    throw new \Exception();
+                }
+                $this->classMetadataWrappers[$className] = new ClassMetadataWrapper($this, $entityRepository, $classMetadata);
             } else {
                 $this->classMetadataWrappers[$className] = null;
             }

lib/ObjectCollection/ObjectCollectionInterface.php

@@ -5,9 +5,7 @@
 interface ObjectCollectionInterface
 {
     /**
-     * @param $object
-     *
-     * @return mixed
+     * @param mixed $object
      */
     public function addOne($object);