Infering the result type of a Query instance

[arnaud-lb]

It may be possible to infer the return type of execute(), getResult(), etc on Query instances when the query string is known statically.

This could be implemented like this:

• Override the Query and AbstractQuery classes so that they have a type parameter, representing the type of their results (e.g. a Query returning User objects would be a Query<User>)
• Add a return type extension for EntityManagerInterface::createQuery(), to infer the result type from the query string, and so that we can tel that createQuery() returns a Query<something>

The ResultSetMapper of a Query provides enough info to infer the result type in the most simple cases (e.g. SELECT u FROM User). This would already be super useful. Other cases might require a custom SqlWalker because the ResultSetMapper doesn't provide any information on nullability, for example.

[arnaud-lb]

PoC: https://github.com/phpstan/phpstan-doctrine/compare/master...arnaud-lb:query-result-type?expand=1

[noemi-salaun]

I think the type can also be infered with QueryBuilder, like in this case

    /**
     * @return VariableModifier[]
     */
    public function getAll(): array
    {
        return $this->getEntityManager()->getRepository(VariableModifier::class)
            ->createQueryBuilder('modifier')
            ->getQuery()
            ->getResult();
    }

[arnaud-lb]

Here is a more advanced branch that implements type inference for most queries: https://github.com/arnaud-lb/phpstan-doctrine/pull/2/files

It will properly infer the result type of any query, including queries with scalar results, joins or left joins, aggregations, functions, and all kinds of expressions (see the related tests)

There are a few things I left for later: sub queries, identity(), size(). These things will cause some parts of the query result to be mixed, so there will be no false typing.

I may eventually submit this in two PRs:

• Generic Query stub + query result type inference and the dynamic return type extension for EntityManager::createQuery()
• Dynamic return type extension for Query::getResult / execute / etc

WDYT ?

[enumag]

@arnaud-lb Sounds great. For now let's focus on the most common cases. Indeed it makes no sense to delay this feature for sub queries and such. Please make a PR where we can discuss the details. You can make it as a draft if unsure about some things.

[arnaud-lb]

Thanks @enumag. I opened a PR at #232

[ondrejmirtes]

#232 merged and released as phpstan-doctrine 1.2.1 :)

[fliespl]

@ondrejmirtes It works fine with basic queries, but once: setLockMode is attached to getQuery() it loses context and reports error.

[ondrejmirtes]

@fliespl Feel free to open a new bug report with more details about it.

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