[TYPO3-english] Extbase repository does not return objects of subclasses (Single Table Inheritance)

[Jochen Fröhlich]

Hi there,

I'm trying to query a repository to retrieve objects representing subclasses that were defined via Single Table Inheritance.
See docs.typo3.org/typo3cms/ExtbaseFluidBook/6-Persistence/5-modeling-the-class-hierarchy.html

It's quite the same problem as described here: forum.typo3.org/index.php?t=msg&goto=736175

What works:
To distinguish the various subclasses I defined a field record_type.
In the backend form, the RecordType can be selected.
The fields are changing according to the definitions for the various subclasses.
The correct RecordType is stored in the DB field record_type.

What doesn't work:
When I try to retrieve objects of the subclasses in the controller, only objects of type BaseClass (which each SubClass extends) are returned.

Below you find my current configuration. TYPO3 / Extbase 8.7.11.

What am I missing? Please let me know if you need any more details.

Thanks in advance for any hints.

Cheers,
Jochen


###################
Directory structure:

[ExtName]
-- [Classes]
---- [Domain]
------ [Model]
-------- BaseClass.php
-------- [Base]
---------- SubClassA.php
---------- SubClassB.php
------ [Repository]
-------- BaseClassRepository.php


###################
TypoScript-Setup of EXT:ExtName:

config.tx_extbase.persistence.classes {
    \VendorName\ExtName\Domain\Model\BaseClass {
        mapping {
            tableName = tx_extname_domain_model_baseclass
            recordType = \VendorName\ExtName\Domain\Model\BaseClass
        }
        subclasses {
            \VendorName\ExtName\Domain\Model\Base\SubClassA = \VendorName\ExtName\Domain\Model\Base\SubClassA
            \VendorName\ExtName\Domain\Model\Base\SubClassB = \VendorName\ExtName\Domain\Model\Base\SubClassB
        }
    }
    \VendorName\ExtName\Domain\Model\SubClassA {
        mapping {
            tableName = tx_extname_domain_model_baseclass
            recordType = \VendorName\ExtName\Domain\Model\SubClassA
        }
    }
    \VendorName\ExtName\Domain\Model\SubClassB {
        mapping {
            tableName = tx_extname_domain_model_baseclass
            recordType = \VendorName\ExtName\Domain\Model\SubClassB
        }
    }
}

plugin.tx_extname_extname {
  view { ... }
  settings { ... }
}


###################
TCA for tx_extname_domain_model_baseclass:

'types' => [
   '\VendorName\ExtName\Domain\Model\Base\SubClassA' => [
      'showitem' => 'record_type, name, ...'
   ],
   '\VendorName\ExtName\Domain\Model\Base\SubClassB' => [
      'showitem' => 'record_type, name, ...'
   ],
]


###################
SubClassA:

namespace VendorName\ExtName\Domain\Model\Base;

use VendorName\ExtName\Domain\Model\BaseClass;

class SubClassA extends BaseClass { ... }


###################
BaseClassController.php: (retrieves only objects of type BaseClass)

public function listAction() {
  $records = $this->baseClassRepository->findAll();
  $this->view->assign('records', $records);
}

###################