Edit modal becomes unresponsive with nested paragraphs and large content sets due to overridden data-drupal-selector in Gin sticky actions

Problem/Motivation

• When editing a paragraph item in a node form (using the Paragraphs module), the edit modal becomes unresponsive under certain conditions. The issue appears when:
• The node contains a large number of paragraph items (approximately 60 or more).
• The paragraph structure includes nested paragraphs.
• After investigation, the problem was traced to a code change introduced in Issue #3489493, where the following line was added:

$button['#attributes']['data-drupal-selector'] = 'gin-sticky-' . $button['#attributes']['data-drupal-selector'];

This overrides Drupal’s core-generated data-drupal-selector, which is essential for JS behavior attachment particularly in modal and AJAX contexts.

Steps to reproduce

1. Enable the Gin theme (version 8.x-3.0).
2. Create a content type with a Paragraphs field that has nested (child) paragraphs.
3. Create a node containing a paragraph item with approximately 60 nested (child) paragraph entries.
4. Attempt to edit the paragraph item.
5. Observe that the edit modal takes a long time to load or becomes unresponsive.

Root Cause

Overwriting data-drupal-selector breaks Drupal's behavior attachment system:

• JavaScript behaviors tied to specific selectors fail to attach or reattach.
• AJAX replacements don't match the modified selector, leading to misbehavior.
• Components like CKEditor, media modals, and buttons may reinitialize infinitely or not at all.

Additional Notes

• Removing the following line resolves the paragraph loading issue in my environment:
• $button['#attributes']['data-drupal-selector'] = 'gin-sticky-' . $button['#attributes']['data-drupal-selector'];
• However, further investigation is needed to understand the original purpose of this change. A proper fix should preserve the intended functionality while avoiding regressions or performance issues—especially in cases involving nested paragraphs and large content structures.
• A patch or conditional implementation may be necessary to ensure compatibility across use cases.