TYPO3.Flow

It comes to an exception like this,

#1355480641: Uncaught Exception Notice: Undefined index: TYPO3\Media\Domain\Model\ImageVariant in Packages\Framework\TYPO3.Flow\Classes\TYPO3\Flow\Reflection\ReflectionService.php line 1461

This is because of these lines,

1    protected function makeChildClassesAggregateRoot(\TYPO3\Flow\Reflection\ClassSchema $classSchema) {
2        foreach ($this->getAllSubClassNamesForClass($classSchema->getClassName()) as $childClassName) {
3            if ($this->classSchemata[$childClassName]->isAggregateRoot()) {
4                continue;

In the given case, the ImageVariant inheritance looks like the following:

Asset (@Entity)
  - SizedAsset (@Entity)
    - ImageVariant (NOT an @Entity!)

The above mentioned method searches in ->classSchemata for the ImageVariant, but as of convention, classSchemata is "Schemata of all classes which can be persisted", so ImageVariant is not there of course, leading to the exception.