Idea: avoid double declare link and type of relation if used via() about active-record HOT 6 OPEN

    public function viaRelation($target, $relationName, $via){
        $target instanceof ActiveRecord || $target = Yii::createObject($target);
        /** @var ActiveQuery $relationQuery */
        $relationQuery = $target->getRelation($relationName);
        $relationQuery->primaryModel = $this;
        return $relationQuery->via($via);
    }

    protected function createRelationQuery($class, $link, $multiple)
    {
        /* @var $class ActiveRecordInterface */
        /* @var $query ActiveQuery */
        $query = $class::find();
        $query->primaryModel = $this;
        $query->link = $link;
        $query->multiple = $multiple;
        return $query;
    }

class Order extends ActiveRecord
{
    public function getOrderItems()
    {
        return $this->hasMany(OrderItem::className(), ['order_id' => 'id']);
    }

    public function getItems()
    {
        return $this->hasMany(Item::className(), ['id' => 'item_id'])
            ->via('orderItems');
    }
}

class OrderItem extends ActiveRecord
{
    public function getItem()
    {
        return $this->hasOne(Item::className(), ['id' => 'item_id']);
    }
}

class Order extends ActiveRecord
{
    public function getOrderItems()
    {
        return $this->hasMany(OrderItem::className(), ['order_id' => 'id']);
    }

    public function getItems()
    {
        return $this->viaRelation(Item::className(), 'item', 'orderItems');
    }
}