in this article, I'll show you how to add Twig Template Suggestions for Form Elements in drupal 8 with hook_theme_suggestions_input_alter():
/**
* @param array $suggestions
* @param array $variables
* @param $hook
*/
function mytheme_theme_suggestions_form_element_alter(array &$suggestions, array $variables, $hook)
{
if (isset($variables['element']['#id'])) {
$id = str_replace("-", "_", $variables['element']['#id']);
$suggestions[] = $hook . '__' . $id;
}
}
and this is the result
<!-- THEME DEBUG -->
<!-- THEME HOOK: 'form_element' -->
<!-- FILE NAME SUGGESTIONS:
* form-element--edit-keys--2.html.twig
x form-element.html.twig
-->
<!-- BEGIN OUTPUT from 'core/themes/classy/templates/form/form-element.html.twig' -->
<div class="js-form-item form-item js-form-type-search form-type-search js-form-item-keys form-item-keys form-no-label">
