Convert classes on wrapper attributes into arrays

Just running the tests against Drupal 8.5, albeit on 11 May 2018 dev past using D8.6 so something fishy could be going on.

Looks good, even with the unrelated test failures.

UnifiedFieldsDiffLayout & SplitFieldsDiffLayout may have some issues, some of the codes a bit hard to follow and probably best dealt with separately. I guess this was tested manually, so assumable the inconsistency is handled in the code.

i.e. row class attributes are defined with both scalar and array, then copied into other table rows inconsistently.

      if (!empty($field['#name'])) {
        $field_label_row = [
          'data' => $field['#name'],
          'colspan' => 8,
          'class' => ['field-name'],
        ];
      }
      if (isset($field['#data']['#left_thumbnail'])) {
        $field_diff_rows['#thumbnail'][1] = [
          'data' => $field['#data']['#left_thumbnail'],
          'class' => '',
        ];
      }

// Usage

          // what I would expect to see...
          'right-row-data' => [
            'data' => isset($field_diff_rows[$key][3]['data']) ? $field_diff_rows[$key][3]['data'] : NULL,
            'class' => isset($field_diff_rows[$key][3]['data']) ? $field_diff_rows[$key][3]['class'] : NULL,
          ],
          // but this is common that looks like it would produce a nested array within the classes array??
          'right-row-sign' => [
            'data' => isset($field_diff_rows[$key][2]['data']) ? $field_diff_rows[$key][2]['data'] : NULL,
            'class' => [
              isset($field_diff_rows[$key][2]['class']) ? $field_diff_rows[$key][2]['class'] : NULL,
              // albeit, wtf?
              isset($field_diff_rows[$key][3]['data']) ? $field_diff_rows[$key][3]['class'] : NULL,
            ],
          ],

Here is an improved patch. I looked up for all class definitions in the module and replaced it with the new [] convention.

Tested and reviewed - working.
The patch changes look reasonable and bringing the module into the convention that attribute class is an array rather than a string.

I think my only worry here is that this will break custom code which expects the attributes to be strings, rather than arrays...am I overthinking it, or is that a reasonable concern?

I think it's the vice versa, I came looking for and found this patch because it was breaking my custom code.

Hi,

Encountered a fatal error with #3367502: Fatal error when using the Diff module yesterday due to class attribute not being an array.

I will secure contrib theme but it would be good that this issue is fixed.

Thanks for the patches.

Converted to an MR and rebased, this conflicted pretty heavily with a change that converted to short array syntax.

I slightly changed some of the ternary conditions, so that the fallback is an empty array and not an array with NULL.

Looks like #2980335: Define CSS classes as an array missed some of these. Rebasing and running fresh pipelines.