Fix return type of getSingleScalarResult

[whatUwant]

Doctrine\ORM\AbstractQuery::getSingleScalarResult() does not have null as a possible type of returned data while NoResultException is listed as one of the possible exceptions thrown.

However NoResultException is thrown only when hydration mode is not HYDRATE_SINGLE_SCALAR.

    public function getSingleResult($hydrationMode = null)
    {
        $result = $this->execute(null, $hydrationMode);

        if ($this->_hydrationMode !== self::HYDRATE_SINGLE_SCALAR && ! $result) {
            throw new NoResultException();
        }

In getSingleScalarResult hydration mode was set to HYDRATE_SINGLE_SCALAR via Doctrine\ORM\AbstractQuery::execute() which makes it impossible to throw that particular type of exception.

[darenas31415]

However NoResultException is thrown only when hydration mode is not HYDRATE_SINGLE_SCALAR.

That's not quite correct as $result = $this->execute(null, $hydrationMode); can still throw NoResultException exception.

Please see screenshot:

How to reproduce:

$qb = $this->em->createQueryBuilder();

$qb->select('p.code')
   ->from('App:Product', 'p')
   ->where('p.name = :name')
   ->setMaxResults(1)
   ->setParameter('name', 'missing');

$code = $qb->getQuery()->getSingleScalarResult();

[derrabus]

You're right. Please send a PR to add back the @throws annotation.

[darenas31415]

Shall I add back only @throws annotation or revert this PR completely?

I can't make getSingleScalarResult return null under any condition, I think the original code was correct.

I'd suggest to revert this PR altogether unless @whatUwant can provide a test case for returning null.

[whatUwant]

It's correct that NoResultException can still be thrown.
null can be returned when aggregate functions such as MIN MAX are used.

$qb = $this->em->createQueryBuilder();

$qb->select('MAX(p.id)')
   ->from('App:Product', 'p')
   ->where('p.name = :name')
   ->setParameter('name', 'missing');

$code = $qb->getQuery()->getSingleScalarResult();

[derrabus]

getSingleScalarResult() with a SELECT on a nullable field should yield null, shouldn't it?

[darenas31415]

getSingleScalarResult() with a SELECT on a nullable field should yield null, shouldn't it?

You are totally right 👍