How to replace a Doctrine entity by an extending one?

[automatix]

In my Symfony 4 app with Doctrine ORM 2.7.0 I got an entity Product, that is part of an external package / system (Akeneo 5), I cannot just modify. Since I need to add a property (stock) to it, I created a class, that extends this entity, and registered it to be used instead of the original one:

src/Tpg/Bundle/AkeneoTpgBundle/Entity/Product.php

<?php
namespace Tpg\Bundle\AkeneoTpgBundle\Entity;

use Akeneo\Pim\Enrichment\Component\Product\Model\Product as AkeneoProduct;

class Product extends AkeneoProduct
{
    private $stock;

    // access methods ...
}

config/services/services.yml

parameters:
  pim_catalog.entity.product.class: 'Tpg\Bundle\AkeneoTpgBundle\Entity\Product'

src/Tpg/Bundle/AkeneoTpgBundle/Resources/config/doctrine/Product.orm.yml

Tpg\Bundle\AkeneoTpgBundle\Entity\Product:
  type: entity
  table: pim_catalog_product
  fields:
    stock:
      type: integer
      nullable: false

But now I got the issue with the aliases. In the SELECT statement different aliases are used for the columns and the condition:

SELECT 
    t1.id AS id_2,
    t1.is_enabled AS is_enabled_3,
    ...
FROM pim_catalog_product t1 
WHERE t0.id = 1207

Which leads to an error, of course.

The mechanism of how that happens is the following:

• In the Doctrine\ORM\Persisters\Entity\BasicEntityPersister#getSelectSQL(...) the getSelectConditionSQL(...)->getSelectConditionStatementSQL(...)->getSelectConditionStatementColumnSQL(...) is called.
• The latter calls the getSQLTableAlias(...) with the $this->class->fieldMappings[$field]['inherited'] as $className argument. And that is the class name of the original entity.
• The getSQLTableAlias(...) checks, whether the passed $className is already in its internal list. It's not, so it sets the alias to 't' . $this->currentPersisterContext->sqlAliasCounter (t0) and increases the counter.
• Then in the BasicEntityPersister#getSelectSQL(...) the getSelectColumnsSQL(...)->getSelectColumnSQL(...) is called.
• The latter calls the getSQLTableAlias(...) with the $this->className as $className argument. And that is the class name of the custom entity.
• The getSQLTableAlias(...) checks, whether the passed $className is already in its internal list. It's not again, so it sets the alias to 't' . $this->currentPersisterContext->sqlAliasCounter, which result now in t1. -- And now we get this mismatch: t1 alias for the columns and t0 for the condition.

Obviously, the issue occurs in the getSelectConditionStatementColumnSQL(). But that place is has been staying unchanged in multiple Doctrine vesions, so that won't be a bug. What is the sense behind it?..

So how to get it working correctly?