Favicon Disappears in Theme Settings Form When Default, Upload, or Path Not Specified

Problem/Motivation

When attempting to set a favicon for a theme in the theme settings, an issue arises if neither default_favicon, favicon_upload, nor favicon_path is explicitly set. This results in the favicon being incorrectly set to FALSE, preventing it from being displayed in the settings form.

The problem originates in the theme.inc file, specifically in line 317, where features.favicon is set to FALSE and cannot be reset to TRUE.

// Generate the path to the favicon.
if ($cache[$theme]->get('features.favicon')) {
  // ... (code snippet)
  $cache[$theme]->set('features.favicon', FALSE);
}

Additionally, in ThemeSettingsForm.php, line 258 ensures that the Favicon details are hidden and cannot be restored:

'input[name="toggle_favicon"]' => ['checked' => FALSE],

Steps to reproduce

• Navigate to the settings page for your theme, e.g., the backend theme Claro.
• Uncheck the checkbox "Use the favicon supplied by the theme" and leave the two fields that appear empty.
• Save the form.
• The form elements for Favicon no longer appear.

Proposed resolution

Add validation to the form fields to ensure that at least one of the settings (default_favicon, favicon_upload, or favicon_path) is provided. This prevents the issue of the favicon being incorrectly set to FALSE and ensures proper functionality.

ThemeSettingsForm.php, l. 453 in validateForm():

// Check that at least one setting for the favicon is provided.
if (empty($form_state->getValue('default_favicon')) && empty($form_state->getValue('favicon_upload')) && empty($form_state->getValue('favicon_path'))) {
  $form_state->setErrorByName({TheRightElement}, $this->t('Please provide at least one of the following: Default Favicon, Favicon Upload, or Favicon Path.'));
}

Remaining tasks

Release notes snippet