Refactor listColumns() method to remove deprecated current() function

[martialblog]

• Since PHP 8.1 calling current() function on objects is deprecated

https://www.php.net/manual/en/function.current.php

[martialblog]

@Thomas-Gelf Tried to handle this like other ImportSources in the Director.

Wasn't sure how to handle empty data. Let me know if there's a better way.

[Thomas-Gelf]

@martialblog: thanks you! IMHO the bug is elsewhere, fetchData() should return an Array of objects:

    /**
     * Returns an array containing importable objects
     *
     * @return array
     */
    abstract public function fetchData();

So, if fetchData ships an object instead, fetchData() should be fixed and return (array) $whatever.

[martialblog]

fetchData() already returns an array as expected return (array) $this->fetchFile

I meant how the listColumns should handle empty data from fetchData(). ImportSourceHook defines it as such, so I assumed an empty array would be fine.

    /**
     * Returns a list of all available columns
     *
     * @return array
     */
    abstract public function listColumns();

[martialblog]

I just realized the on objects part in Calling this function on objects is deprecated. So calling it on arrays is fine, right?

[Thomas-Gelf]

Right, and empty data is an empty array. So this should never trigger a related notice. Checking for an empty result is still useful, as (array) false evaluates to [false], which would be presented as a single column named '' (emtpy string). Returning no column at all is better. However, it makes no difference in practice, as you're not able to store a sync property referencing an empty string