drupal_get_js() stable sort / drupal_add_js automatic weight

Status: Duplicate

Solution moved to #1670450: drupal_get_js() stable sort / drupal_add_js automatic weight

Original description

There is a weight and sorting issue with drupal_add_js, if that is called multiple times for the same js. This happens easily with the ['#attached']['js'] thing.

Understanding the problem

This is our test pseudocode.
Obviously, we want $script0 to be included before $script1.

$element['a']['#attached']['js'][$script0] = array();
$element['a']['#attached']['js'][$script1] = array();
$element['b']['#attached']['js'][$script0] = array();
$element['b']['#attached']['js'][$script1] = array();

Now in drupal_add_js():

  // Tweak the weight so that files of the same weight are included in the
  // order of the calls to drupal_add_js().
  $options['weight'] += count($javascript) / 1000;
  [..]
        $javascript[$options['data']] = $options;

Effect:
When the script is added for the second time, no new elements are added to the $javascript array. The original weight of the scripts is overridden. Now they both have the same weight.

Later in drupal_get_js():

  uasort($items, 'drupal_sort_css_js');

The sort is not stable, as none of php sort algorithms is.
Thus, it can happen that $script1 is included before $script0. Ouch!

Solution

Solution A (preferable):
- implement a stable sort
- make sure css and js items are always moved to the end of the array, when they are included again.
- the micro-weight will now be pointless.

Solution B:
Implement a counter for the micro-weight, instead of just count($javascript).

Related issues

The same problem has been reported in
#1388546: Adding CSS or JS files twice changes weight and
#1458436: drupal_add_js/css() weight trickery fails if called for the same files multiple times (duplicate)

I have no idea if this applies to D8, so I just report for D7.