Initializing a collection overwrites nulled field

[insel-maz]

Bug Report

Q	A
BC Break	no?
Version	3.2.1 down to 2.x

Summary

When Doctrine fetches the entities for a PersistentCollection it overwrites the programmatically set null values in association fields for already managed (in the identity map) entities.

This happens by the if statement in

orm/src/Internal/Hydration/ObjectHydrator.php

Line 434 in 205b2f5

if (! $reflFieldValue || isset($this->hints[Query::HINT_REFRESH]) || $this->uow->isUninitializedObject($reflFieldValue)) {

.

Current behavior

The association field, which was just set to null by code, is overwritten with the persisted peer entity.

How to reproduce

In the following example there is a one-to-one association. One side gets set to null, but when a collection containing the entity is loaded, the field is restored with the peer entity.

https://github.com/insel-maz/doctrine-bug-collection-initialization-overwrites-field

Expected behavior

If an entity is already managed (in the identity map) Doctrine should not change the fields when fetching the database records for a PersistentCollection.