Symfony Api Platform: Ordering results by custom entity method

Question

In my Symfony Api platform project, I have an entity Community with a custom method getTotalMembers() that returns the number of members in the community. However, when I try to order my results, it doesn't work.

#[ApiFilter(OrderFilter::class, 
      properties: ['id', 'name', 'totalMembers'], 
      arguments: ['orderParameterName' => 'order']
)]

/**
 * @return int current number of users that are members of this community
 */
#[Groups(['community:read','community:read_list'])]
public function getTotalMembers(): ?int
{
    return $this->members->count();
}

Is there a simple way to make it work?

Answer 1

After a lot of struggle I was able to solve partially the issue with custom State processor on the many to many join relationship table. It calls method that adds or removes 1 from regular field that I can use for sorting.

<?php

namespace App\State;

use ApiPlatform\Metadata\DeleteOperationInterface;
use App\Entity\Membership;
use ApiPlatform\Metadata\Operation;
use ApiPlatform\State\ProcessorInterface;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Component\DependencyInjection\Attribute\Autowire;

final class MembershipStateProcessor implements ProcessorInterface
{
    public function __construct(
        #[Autowire(service: 'api_platform.doctrine.orm.state.persist_processor')]
        private ProcessorInterface $persistProcessor,
        #[Autowire(service: 'api_platform.doctrine.orm.state.remove_processor')]
        private ProcessorInterface $removeProcessor,
        private EntityManagerInterface $entityManager,
    ) {
    }
    /**
     * @param Membership $data
     */
    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): Membership|null
    {
        // decrease amount of members inside communities
        if ($operation instanceof DeleteOperationInterface) {
            $subreddit = $data->getSubreddit();
            $subreddit->setTotalMembers(isDelete: true);
            $this->entityManager->persist($subreddit);
            $this->removeProcessor->process($data, $operation, $uriVariables, $context);
            return null;
        }

        // increase amount of members inside communities
        $subreddit = $data->getSubreddit();
        $subreddit->setTotalMembers(isDelete: false);
        $this->entityManager->persist($subreddit);
        return $this->persistProcessor->process($data, $operation, $uriVariables, $context);
    }
}

The problem now, however, is that factories do not trigger this class and so entities made with factories aren't counted in, which hinders my ability to test this future.