Fixed saving a model after fetching its related records

CHANGELOG-4.0.md

@@ -31,6 +31,7 @@
 - Query Builder's `GROUP BY` field is now always an array. [#13962](https://github.com/phalcon/cphalcon/pull/13962)
 - Renamed `Phalcon\Paginator\Adapter::getPaginate()` to `paginate()` in documentation/tests (originally renamed in 4.0.0-alpha.1). [#13973](https://github.com/phalcon/cphalcon/pull/13973)
 - Fixed the exception message in `Phalcon\Security::computeHmac()` by removing `"%s"` from output.
+- Fixed `Mvc\Model::save()` throwing an exception after fetching its related records (many/many-to-many) via `__get()` [#13985](https://github.com/phalcon/cphalcon/pull/13985)
 
 ## Removed
 - Removed `arrayHelpers` property from the Volt compiler. [#13925](https://github.com/phalcon/cphalcon/pull/13925)

phalcon/Mvc/Model.zep

@@ -288,8 +288,11 @@ abstract class Model implements EntityInterface, ModelInterface, ResultInterface
 
                 /**
                  * We store relationship objects in the related bag
+                 *
+                 * Removed temporarily.
+                 * See https://github.com/phalcon/cphalcon/issues/13964
                  */
-                let this->related[lowerProperty] = result;
+                // let this->related[lowerProperty] = result;
             }
 
             return result;

tests/integration/Mvc/Model/Refactor-ModelsRelationsMagicCest.php

@@ -23,6 +23,7 @@ public function testModelsMysql(IntegrationTester $I)
         $this->setDiMysql();
 
         $this->executeQueryRelated($I);
+        $this->executeSaveAfterQueryRelated($I);
         $this->executeSaveRelatedBelongsTo($I);
     }
 
@@ -54,6 +55,12 @@ public function testModelsSqlite()
         $this->_executeSaveRelatedBelongsTo($connection);
     }*/
 
+    /**
+     * Test for issue: #13964
+     * See: https://github.com/phalcon/cphalcon/issues/13964
+     *
+     * @param IntegrationTester $I
+     */
     private function executeQueryRelated(IntegrationTester $I)
     {
 
@@ -78,6 +85,22 @@ private function executeQueryRelated(IntegrationTester $I)
         $I->assertEquals($originalAlbum->id, $album->id);
     }
 
+    private function executeSaveAfterQueryRelated(IntegrationTester $I)
+    {
+        $album = Albums::findFirst();
+        $artist = $album->artist;
+
+        $I->assertTrue($album->save());
+
+        $artist->albums;
+
+        $I->assertTrue($artist->save());
+
+        $album->songs;
+
+        $I->assertTrue($album->save());
+    }
+
     private function executeSaveRelatedBelongsTo(IntegrationTester $I)
     {
         $connection = $this->getService('db');