[Fix] morphTo relationship

src/Relations/MorphTo.php

@@ -16,7 +16,11 @@ public function addConstraints()
             // For belongs to relationships, which are essentially the inverse of has one
             // or has many relationships, we need to actually query on the primary key
             // of the related models matching on the foreign key that's on a parent.
-            $this->query->where($this->ownerKey, '=', $this->parent->{$this->foreignKey});
+            $this->query->where(
+                $this->ownerKey ?: $this->query->getModel()->getKeyName(),
+                '=',
+                $this->parent->{$this->foreignKey},
+            );
         }
     }
 

tests/Models/Photo.php

@@ -17,4 +17,9 @@ public function hasImage(): MorphTo
     {
         return $this->morphTo();
     }
+
+    public function hasImageWithCustomOwnerKey(): MorphTo
+    {
+        return $this->morphTo(ownerKey: 'cclient_id');
+    }
 }

tests/RelationsTest.php

@@ -470,6 +470,25 @@ public function testMorph(): void
         $relations = $photos[1]->getRelations();
         $this->assertArrayHasKey('hasImage', $relations);
         $this->assertInstanceOf(Client::class, $photos[1]->hasImage);
+
+        // inverse
+        $photo = Photo::query()->create(['url' => 'https://graph.facebook.com/hans.thomas/picture']);
+        $client = Client::create(['name' => 'Hans Thomas']);
+        $photo->hasImage()->associate($client)->save();
+
+        $this->assertCount(1, $photo->hasImage()->get());
+        $this->assertInstanceOf(Client::class, $photo->hasImage);
+        $this->assertEquals($client->_id, $photo->hasImage->_id);
+
+        // inverse with custom ownerKey
+        $photo = Photo::query()->create(['url' => 'https://graph.facebook.com/young.gerald/picture']);
+        $client = Client::create(['cclient_id' => (string) (new ObjectId()), 'name' => 'Young Gerald']);
+        $photo->hasImageWithCustomOwnerKey()->associate($client)->save();
+
+        $this->assertCount(1, $photo->hasImageWithCustomOwnerKey()->get());
+        $this->assertInstanceOf(Client::class, $photo->hasImageWithCustomOwnerKey);
+        $this->assertEquals($client->cclient_id, $photo->has_image_with_custom_owner_key_id);
+        $this->assertEquals($client->_id, $photo->hasImageWithCustomOwnerKey->_id);
     }
 
     public function testHasManyHas(): void