Filter Format validation bug, not iterating through all rows.

Problem/Motivation

This code needs updating in order to actually iterate through all the rows:

      if (!empty($button_groups[0])) {
        foreach ($button_groups[0] as $button_group) {
          foreach ($button_group['items'] as $item) {
            $buttons[] = $item;
          }
        }
      }

The $button_groups array is an array of rows. It's only checking the first row.

This was found by phenaproxima at #2994699-52: Create a CKEditor plugin to select and embed a media item from the Media Library.12.

Why are we limiting this to the first button group? Shouldn't we loop through all of them?

I checked and this is indeed a bug.

Proposed resolution

The code should be replaced like this:

     $buttons = [];
-    $button_groups = json_decode($button_groups, TRUE);
-    if (!empty($button_groups[0])) {
-      foreach ($button_groups[0] as $button_group) {
-        foreach ($button_group['items'] as $item) {
-          $buttons[] = $item;
-        }
+    $button_groups = Json::decode($button_groups, TRUE);
+
+    foreach ($button_groups as $button_row) {
+      foreach ($button_row as $button_group) {
+        $buttons = array_merge($buttons, array_values($button_group['items']));
       }
     }

And for test coverage, change the text format button config so it has two row.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet