`Folder::searchByMime` does not work for folder under group folder

[paulijar]

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Steps to reproduce

Prerequisite: Have a group folder configured and a sub-folder under it with some files. In the example below, I had a user named root who had access to a group folder with hierarchy like this:

group_folder
|
--> subfolder
|   |
|   --> file2.md
|   |
|   --> file3.md
|
--> file1.md  

Register the command class shown below to some app and run it with occ for the folders group_folder and group_folder/subfolder:

The source code of the occ command used above:

namespace OCA\Music\Command; // set to something suitable, I registered under the Music app as that was convenient for me

use OCP\Files\Folder;
use OCP\Files\IRootFolder;
use OCP\Files\NotFoundException;
use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputArgument;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class SearchByMime extends Command {

	private IRootFolder $rootFolder;

	public function __construct(IRootFolder $rootFolder) {
		parent::__construct();
		$this->rootFolder = $rootFolder;
	}

	protected function configure() {
		$this
			->setName('search-by-mime')
			->setDescription('Test the Folder::searchByMime function')
			->addArgument(
				'base_folder',
				InputArgument::REQUIRED,
				'path to the base folder of the search'
			)
			->addArgument(
				'mime',
				InputArgument::REQUIRED,
				'mime (possibly partial) to search under base_folder'
			)
		;
	}

	protected function execute(InputInterface $input, OutputInterface $output) {
		$path = $input->getArgument('base_folder');
		try {
			$folder = $this->rootFolder->get($path);
		} catch (NotFoundException $e) {
			// pass
		}

		if (!($folder instanceof Folder)) {
			$output->writeln("<error>$path</error> is not a valid folder path");
			return 1;
		}

		$mime = $input->getArgument('mime');
		$found = $folder->searchByMime($mime);
		$count = \count($found);

		$output->writeln("Under folder <info>$path</info>, there are <info>$count</info> nodes matching mime <info>$mime</info>:");

		foreach ($found as $node) {
			$output->writeln($node->getPath());
		}

		return 0;
	}
}

Expected behaviour

Folder::searchByMime should find matching files also when used on a folder residing inside a group folder.

Actual behaviour

Folder::searchByMime does not find any matching files when used on a folder residing inside a group folder. Using the function on the group folder itself finds those files.

This is the root cause of the bug owncloud/music#1195.

Server configuration

Operating system: Linux 6.1.19-v8+ aarch64

Web server: N/A

Database: SQLite 3.34.1

PHP version: 8.2.27

Nextcloud version: 30.0.2 RC1

Team folders version: 18.0.8

Updated from an older Nextcloud/ownCloud or fresh install: fresh

Where did you install Nextcloud from: https://download.nextcloud.com/server/

Are you using external storage, if yes which one: no

Are you using encryption: no

Are you using an external user-backend, if yes which one: no

Client configuration

N/A

Logs

N/A