Both Vertical and Horizontal tabs on the same page do not work

We're seeing a similar issue fixed by this patch - thank you!

In our case, two content types have both vertical and horizontal tabs. The first set of horizontal tabs disappears entirely when the module is upgraded from 3.6 to 4.0.0. The missing tab group reappears when the patch is applied. No 'required' functionality is involved. None of the other tab groups are affected, only the first one.

I'm happy to provide more information or do more testing if that would help.

Claude Code says:

PHP Changes (field_group.module)

field_group_get_settings_key() — correct approach, one concern

The key construction ($group->format_type . $group->format_settings['direction']) correctly produces tabsvertical and tabshorizontal, which align with the JS dispatch lookup.

However, the drupalSettings attachment on lines 455-461 and 485-491 uses = (assignment), not += (merge):

  $element['#attached']['drupalSettings']['field_group'] = [
      field_group_get_settings_key($group) => [ ... ],
  ];

This replaces the entire field_group settings array each time a group is processed. If a page has three groups (e.g. vertical tabs, horizontal tabs, and an accordion), only the last one processed will have its settings survive. This was a pre-existing bug — the branch doesn't introduce it — but it means this fix may still not fully work on pages with more than two field groups. Worth noting in the issue, though not something this branch needs to solve.

Docblock: Missing blank line between @param and @return (Drupal coding standards require it). Line 438 → 439 should have a blank line.

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JS Changes (formatters/tabs/tabs.js)

Clean refactor. The logic is extracted into a standalone executeTabProcessing function, and two effect objects reference it:

  Drupal.FieldGroup.Effects.processTabsVertical = { execute: executeTabProcessing };
  Drupal.FieldGroup.Effects.processTabsHorizontal = { execute: executeTabProcessing };

The dispatch in field_group.js:30-39 iterates Drupal.FieldGroup.Effects, derives the settings key by lowercasing the effect name and stripping process, then looks up settings.field_group[type]. The keys produced:

  - processTabsVertical → tabsvertical (matches PHP key tabs + vertical)
  - processTabsHorizontal → tabshorizontal (matches PHP key tabs + horizontal)

This works correctly. The direction value is passed through in groupInfo.settings.direction, so the inner logic ($this.data(\${direction}Tab`)`) continues to resolve properly.

Backward compatibility: The old processTabs effect name is removed. Any third-party code that referenced Drupal.FieldGroup.Effects.processTabs directly will break. This is unlikely but worth mentioning in the change record.

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Key Points

1. The dispatch key matching is correct — PHP and JS align properly
2. The = vs += for drupalSettings is a pre-existing issue, not introduced here, but it limits how many distinct field group types can coexist on one page
3. Minor: docblock missing blank line before @return
4. Minor: removal of processTabs is a (small) API break for any code referencing it directly

Thank you for the fixes and the tests. LGTM! Merging!