[12.x] Introduce Reflector methods for accessing class attributes

[daniser]

New Reflector methods getClassAttribute and getClassAttributes have been added to simplify/unify access to class attributes.

getClassAttribute method returns instance of desired attribute if found, or null otherwise.

getClassAttributes method is more suited if you want to access repeatable attributes and/or collect attributes up inheritance chain. It returns collection of attribute instances, grouped by class name if ancestor lookup is enabled. This simplifies aggregate operations on child and parent attributes, for example configuration merging:

use Illuminate\Support\Reflector;

#[Attribute(Attribute::TARGET_CLASS | Attribute::IS_REPEATABLE)]
class ConfigAttr
{
    public function __construct(public array $config) {}
}

#[ConfigAttr(['c' => 3])]
class ParentClass
{
    public static function getConfig(): array
    {
        return Reflector::getClassAttributes(static::class, ConfigAttr::class, true)->flatten()->flatMap->config->all();
    }
}

#[ConfigAttr(['a' => 1]), ConfigAttr(['b' => 2])]
class ChildClass extends ParentClass {}

ChildClass::getConfig();
// ['a' => 1, 'b' => 2, 'c' => 3]

Both methods are properly typehinted.

Update: functions moved into Reflector class.