Need to deep merge options for compatibility with other modules

Issue information

From user: anybody

Related to !14 (merged)

Contribution record

Fork management

Problem/Motivation

Follow-up on #3331630: Compatibility with other modules, options being overwritten.

I just read the code in the commit and I think it might instead need an array_merge_deep so that all values are preserved and the second array does not override the first one?

For example for attributes:

<?php
$a = [
  'attributes' => ['class' => ['a']],
];
$b = [
  'attributes' => ['class' => ['a']],
];
$c = array_merge($a, $b);
?>

will result in

array(1) {
  ["attributes"]=>
  array(1) {
    ["class"]=>
    array(1) {
      [0]=>
      string(1) "b"
    }
  }
}

but I think we need to preserve all values here.

This may also lead to conflicts, if one attribute *should* override, but I don't think we can handle that!

Steps to reproduce

Proposed resolution

Remaining tasks

1. Discuss:
   • Use array_merge
   • Use array_merge_recursive
   • Use one of https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Component%21Utility%21NestedArray.php/class/NestedArray/10
   • Only merge certain attributes recursively
2. Implement
3. Test
4. Release

User interface changes

API changes

Data model changes