Add type detection for PDOStatement::fetchAll(PDO::FETCH_CLASS, SomeClass::class)

[thbley]

Example fetchAll: https://psalm.dev/r/a9b0c85b47

Add type detection for PDOStatement::fetchAll(PDO::FETCH_CLASS, SomeClass::class): SomeClass[]|false;

Currently PDOStatement::fetchAll() is currently defined as:

'PDOStatement::fetchAll' => ['array', 'mode='=>'int', '...args='=>'mixed'],

which infers to array<array-key, mixed> instead of array<array-key, SomeClass>

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a9b0c85b47

<?php

class Task {}

class Database {
    /**
     * @return Task[]
     */
    public function getTasks(): array
    {
        $database = new PDO('');
        return $database
            ->query('SELECT id, title, duedate FROM task')
			->fetchAll(PDO::FETCH_CLASS, Task::class) ?: [];
    }
}

Psalm output (using commit 086b943):

INFO: MixedReturnTypeCoercion - 12:16 - The type 'array<array-key, mixed>' is more general than the declared return type 'array<array-key, Task>' for Database::getTasks

INFO: MixedReturnTypeCoercion - 7:16 - The declared return type 'array<array-key, Task>' for Database::getTasks is more specific than the inferred return type 'array<array-key, mixed>'

[orklah]

Thanks for the feedback!

Turns out we already do something similar for fetch: https://github.com/vimeo/psalm/blob/master/src/Psalm/Internal/Provider/ReturnTypeProvider/PdoStatementReturnTypeProvider.php#L34

It should be pretty easy to adapt this to work with fetchAll too

[robchett]

Looks like this issue is resolved? There was quite a lot of discussion on the merge request, but it feels beyond the scope of the tags :)

[thbley]

Yes, is resolved.