Fix user.data ServiceNotFoundException when using Gin as distribution installer theme

Quick fix for this with custom --gin-color-primary accent

Not to load not styled gin accent while installing.
As no user Gin setting yet and no user service yet.

Removing

/**
 * Implements hook_css_alter().
 */
function hook_css_alter(&$css, AttachedAssetsInterface $assets) {

  global $install_state;
  if (isset($install_state) && empty($install_state['installation_finished'])) {
    // Not to load not styled gin accent while installing.
    // As no user Gin setting yet and not user service yet.
    $gin_theme_css_path = \Drupal::service('extension.list.theme')->getPath('gin') . '/dist/css';
    unset($css[$gin_theme_css_path . '/base/gin.css']);
  }

}

Looking for a better fix tho

Obs, forgot the patch

Thank you all for your work on this issue! It does work as far as I tested.
However, Did you think about fixing the backend part directly and only in GinSettings to keep things simple and tidy?
I don't want to pollute current patches but here is what seems to work for me.

diff --git a/src/GinSettings.php b/src/GinSettings.php
index 0bb6e42..15a111f 100644
--- a/src/GinSettings.php
+++ b/src/GinSettings.php
@@ -27,7 +27,7 @@ class GinSettings implements ContainerInjectionInterface {
   /**
    * The user data service.
    *
-   * @var \Drupal\user\UserDataInterface
+   * @var \Drupal\user\UserDataInterface|null
    */
   protected $userData;
 
@@ -41,15 +41,15 @@ class GinSettings implements ContainerInjectionInterface {
   /**
    * Settings constructor.
    *
-   * @param \Drupal\user\UserDataInterface $userData
-   *   The user data service.
    * @param \Drupal\Core\Session\AccountInterface $currentUser
    *   The current user.
    * @param \Drupal\Core\Config\ConfigFactoryInterface $configFactory
    *   The config factory.
    */
-  public function __construct(UserDataInterface $userData, AccountInterface $currentUser, ConfigFactoryInterface $configFactory) {
-    $this->userData = $userData;
+  public function __construct(AccountInterface $currentUser, ConfigFactoryInterface $configFactory) {
+    if (\Drupal::hasService('user.data')) {
+      $this->userData = \Drupal::service('user.data');
+    }
     $this->currentUser = $currentUser;
     $this->configFactory = $configFactory;
   }
@@ -59,7 +59,6 @@ class GinSettings implements ContainerInjectionInterface {
    */
   public static function create(ContainerInterface $container) {
     return new static(
-      $container->get('user.data'),
       $container->get('current_user'),
       $container->get('config.factory')
     );
@@ -121,7 +120,7 @@ class GinSettings implements ContainerInjectionInterface {
    *   The account object. Current user if NULL.
    */
   public function setAll(array $settings, AccountInterface $account = NULL) {
-    if (!$account) {
+    if (!$account || !$this->userData) {
       $account = $this->currentUser;
     }
     // All settings are deleted to remove legacy settings.
@@ -137,7 +136,7 @@ class GinSettings implements ContainerInjectionInterface {
    *   The account object. Current user if NULL.
    */
   public function clear(AccountInterface $account = NULL) {
-    if (!$account) {
+    if (!$account || !$this->userData) {
       $account = $this->currentUser;
     }
     $this->userData->delete('gin', $account->id());
@@ -164,7 +163,7 @@ class GinSettings implements ContainerInjectionInterface {
    *   TRUE or FALSE.
    */
   public function userOverrideEnabled(AccountInterface $account = NULL) {
-    if (!$account) {
+    if (!$account || !$this->userData) {
       $account = $this->currentUser;
     }
     return $this->allowUserOverrides() && (bool) $this->userData->get('gin', $account->id(), 'enable_user_settings');

Upping #26 as patch as it's working for me and I prefer this approach for fixing the problem exactly where it occurs. Credits need to go to @NicolasGraph.

@leymannx can you create a MR for this? TY in advance!

Thanks y'all for your participation in addressing this 🙌

Automatically closed - issue fixed for 2 weeks with no activity.