Drupal 11.3 introduces an important shift for theme and module developers:
the long-standing automatic discovery of template_preprocess_HOOK() functions is now deprecated, along with the file and includes keys in hook_theme().
These patterns have been around since Drupal 7 and worked well in the procedural era. But with modern autoloading and class-based preprocessors, they’re no longer necessary — and now officially discouraged.
In this article, we’ll cover: