hook_preprocess_node and language not specified

I do not understand the question.
$variables is from 'function mymodule_preprocess_node(array &$variables) : void'

drupal 11.3.x:
If I remove the $node = $variables['node']; in my module_preprocess_node, I get this error:
Error: Call to a member function language() on null in Drupal\locale\Hook\LocaleThemeHooks->preprocessNode() (line 99 of core/modules/locale/src/Hook/LocaleThemeHooks.php).

drupal 11.2.10: output of dpm($variables); in mymodule_preprocess_node

$variables array (15)
    elements => array (66)
    theme_hook_original => string (4) "node"
    attributes => array (1)
    title_attributes => array (0)
    content_attributes => array (0)
    title_prefix => array (0)
    title_suffix => array (1)
    db_is_active => boolean true
    is_admin => boolean true
    logged_in => boolean true
    user => Drupal\Core\Session\AccountProxy#5305 (5)
    directory => string (29) "themes/custom/interelectronix"
    #cache => array (1)
    language => string (2) "en"
    language_direction => string (3) "ltr"

In drupal 11.3.x I do not get an output for dpm($variables);. As described before, I get this error:

Error: Call to a member function language() on null in Drupal\locale\Hook\LocaleThemeHooks->preprocessNode() (line 99 of core/modules/locale/src/Hook/LocaleThemeHooks.php).

I use hook_preprocess_node in 3 custom modules and in my custom theme.

Installed and enabled contrib modules:
action
address
admin_toolbar
admin_toolbar_tools
avif
bamboo_twig
bamboo_twig_config
bamboo_twig_i18n
bamboo_twig_loader
bamboo_twig_path
block_class
cloudflare
convert_bundles
cookies
critical_css
csp
csv_serialization
ctools
ctools_entity_mask
devel
diff
ds
entity_clone
entity_reference_revisions
extra_field
fences
field_group
field_permissions
field_token_value
file_mdm
file_mdm_exif
file_mdm_font
file_to_media
gin_toolbar
google_analytics
image_effects
image_style_quality
image_style_warmer
imagemagick
imce
inline_entity_form
jquery_ui
jquery_ui_datepicker
jquery_ui_tabs
jquery_ui_tooltip
key
kint
klaro
language_switcher_extended
lazy
linkit
manage_display
markdown_easy
metatag
metatag_hreflang
metatag_views
minifyhtml
node_read_time
node_revision_delete
paragraph_view_mode
paragraphs
paragraphs_table
pathauto
pathologic
potx
queue_ui
redirect_404
redirect
replicate
replicate_ui
restui
schema_metatag
search_api_db
search_api
search_api_block
search_api_exclude_entity
smtp
sophron
taxonomy_term_depth
tmgmt_content
tmgmt_locale
tmgmt_config
tmgmt
tmgmt_file
tmgmt_language_combination
tmgmt_local
tmgmt_deepl_glossary
tmgmt_deepl
tmgmt_microsoft
toc_js
token
translation_views
twig_tools
twig_tweak
twig_vardumper
ultimate_cron
upgrade_status
views_bulk_operations
views_data_export
views_fields_on_off
views_infinite_scroll
views_term_hierarchy_weight_field
watchdog_prune
webform_node
webform_templates
webform_ui
webform
webform_spam_words
xmlsitemap
xmlsitemap_custom

dpm($variables) is the first line in my preprocess_node function - like this:

function mymodule_preprocess_node(array &$variables) : void {
  dpm($variables);
  // $node = $variables['node'];
}

And I remove all other code from my preprocess_node function.

I have 3 custom modules with hook_preprocess_node and also one in my theme.

1. function ix_helper_preprocess_node(&$variables) : void {
2. function ix_paragraph_rows_preprocess_node(array &$variables) : void {
3. function ix_vimeo_preprocess_node(&$variables) : void {
4. function theme_preprocess_node(&$variables) : void {

The functions are called in this order.

Please keep in mind, that I get this errors only on a special content type, where the nodes have language setting 'Not specified' (und) and fields are set to 'Not translatable' and the default language is set to 'en'. More languages exist in the site (de, fr, ...).

If I call a content type, where the nodes have language setting = 'en' and are translated, the error do not occur.

@cilefen I setup XDebug and set a breakpoint for errors generally and a breakpoint before the line
Error: Call to a member function bundle() on null in mymodule_preprocess_node() (line 114 of modules/custom/mymodule/mymodule.module).
where the error occur.

In the Locals I get

$node = uninitialized
$variables = array(15)
  elements = array()66
  theme_hook_original = "node"
  attributes = array(1)
  title_attributes = array(0)
  content_attributes = array(0)
  title_prefix = array(0)
  title_suffix = array(1)
  db_is_active = true
  is_admin = true
  logged_in = true
  user = Drupal\Core\Session\AccountProxy
  directory = "themes/custom/interelectronix
  #cache = array(1)
  language = "en"
  language_direction = "ltr"

No $variables['node'] available.

But also no error thrown before.

In my code, I use $variables['node'] 3 times - and nowhere unset($variables['node']).

Where is $variables['node'] created the first time? Perhaps it's not created, as language is 'en' and the content type has language 'und'?

I set a breakpoint in NodeThemeHooks.php (preprocessNode) at the end of the function and one in my module, which causes the first error.

If I call a node content type, which causes no error, XDebug stops at the breakpoint in NodeThemeHooks and $variables['node'] is set.

If I call the node content type, which causes the error (language = 'Not specified'), the breakpoint in NodeThemeHooks is not used and XDebug stops at the second breakpoint in my custom module and no $variables['node'] is set.

In my opinion, the crux of the matter is/are the language handling?!

@cilefen Call stack in for my preprocess_node function:

ix_paragraph_rows_preprocess_node
Drupal\Core\Extension\ModuleHandler->invoke
Drupal\Core\Theme\ThemeManager->{closure:/var/www/html/web/core/lib/Drupal/Core/Theme/ThemeManager.php:293-319}
Drupal\Core\ThemeManager->render
Drupal\Core\Render\Renderer->doRender
Drupal\Core\Render\Renderer->render
Drupal\Core\Render\MainContent\HtmlRenderer->{closure:/var/www/html/web/core/lib/Drupal/Core/MainContent\HtmlRenderer.php:235-243}
Drupal\Core\Render\Renderer::{closure:/var/www/html/web/core/lib/Drupal/Core/Render\Renderer.php:634-634}
{fiber:FFFF8A21A640

@nicxvan I think - probably - the content type settings are defined in the UI, but goes back to drupal 7.
Special thing could be, that there are nodes of this content type, which are translated (language en + de, fr, ...) and nodes, which are not translated (language 'Not specified').

Since I am not very experienced with debugging, I would be grateful for more detailed instructions. But I think, I found the place to set the breakpoint:
file: web/core/lib/Drupal/Core/Extension/ModuleHandler.php

  public function invoke($module, $hook, array $args = []) {
    $list = $this->getHookImplementationList($hook);
    $listeners = $list->getForModule($module);
    if ($listeners) {

The first break shows:

$args = array(3)
  0 = array(14)
  1 = "entity_page_title
  ...

The second break shows:

$args = array(3)
  0 = array(19)
  1 = "node"
  ...

If I call a working content type, 0 = array(...) - which I think corresponds with $variables - contain a line with node = Drupal\node\EntityNode.

If I call a not working content type, there is no node = Drupal\node\EntityNode in this 0 = array().

I hope, this is the information @cilefen you want to have. So the "node" information is never included.

There are only 4 times, the breakpoint in function invoke() appears, before the error on missing $node = $variables['node'] is thrown:

1. run

$args = array(3)
  0 = array(14)
  1 = "entity_page_title"
$hook = "preprocess"
$module = "contextual"
  

2. run

$args = array(3)
  0 = array(12)
  1 = "node"
$hook = "preprocess"
$module = "contextual"
  

3. run

$args = array(3)
  0 = array(13)
  1 = "node"
$hook = "preprocess_node"
$module = "ix_helper"

4. run
<code>$args = array(3)
  0 = array(13)
  1 = "node"
$hook = "preprocess_node"
$module = "ix_paragraph_rows"
  

After that the error is thrown. In none of the $args['0'] arrays is a $args['0']['node'] available.

@nicxvan: I applied the patch, but unfortunately the same behaviour/error.

The problem persists. Are there any ideas on how to find the cause?

I still can't update to Drupal 11.3.x. Are there any suggestions on how to resolve this issue?

After much research, it seems I have found the solution.

1. In Drupal 11.3, node preprocessing moved to initial preprocess (NodeThemeHooks::preprocessNode) in NodeThemeHooks.php (line 43).
2. template_preprocess_node() is now deprecated in node.module (line 272).
3. My registry alter in ix_datasheet.module (line 60) (and similarly in ix_paragraph_rows.module (line 74)) copies preprocess functions from base hook, but not initial preprocess.
4. Result: for those custom node suggestions, core node hydration may not run, $variables['node'] can be null, then crash at ix_paragraph_rows.module (line 113).

I changed:

function ix_datasheet_theme_registry_alter(&$theme_registry) : void {
  $extension   = '.html.twig';
  $module_path = \Drupal::service('extension.path.resolver')->getPath('module', 'ix_datasheet');
  $files = \Drupal::service('file_system')->scanDirectory($module_path . '/templates', '/' . preg_quote($extension) . '$/', [
    'key' => 'filename',
    'recurse' => FALSE,
  ]);

  $fs = \Drupal::service('file_system');

  foreach ($files as $file) {
    $template = $fs->basename($file->filename, $extension);
    $theme    = str_replace('-', '_', $template);
    $__expt = explode('__', $theme, 2);
    $base_theme = empty($__expt[0]) ? null : $__expt[0];
    $specific = empty($__expt[1]) ? null : $__expt[1];
    if (!empty($specific) && isset($theme_registry[$base_theme])) {
      $theme_info = array(
        'template'   => $template,
        'path'       => $fs->dirname($file->uri),
        'render element'  => $theme_registry[$base_theme]['render element'],
        'base hook'  => $base_theme,
        'type'       => 'module',
        'theme path' => $module_path,
        'preprocess functions' => $theme_registry[$base_theme]['preprocess functions'],
      );

      $theme_registry[$theme] = $theme_info;
    }
  }
}

to this:

function ix_datasheet_theme_registry_alter(&$theme_registry) : void {
  $extension   = '.html.twig';
  $module_path = \Drupal::service('extension.path.resolver')->getPath('module', 'ix_datasheet');
  $files = \Drupal::service('file_system')->scanDirectory($module_path . '/templates', '/' . preg_quote($extension) . '$/', [
    'key' => 'filename',
    'recurse' => FALSE,
  ]);

  $fs = \Drupal::service('file_system');

  foreach ($files as $file) {
    $template = $fs->basename($file->filename, $extension);
    $theme    = str_replace('-', '_', $template);
    $__expt = explode('__', $theme, 2);
    $base_theme = empty($__expt[0]) ? null : $__expt[0];
    $specific = empty($__expt[1]) ? null : $__expt[1];
    if (!empty($specific) && isset($theme_registry[$base_theme])) {
      $base_info = $theme_registry[$base_theme];
      $theme_info = $base_info;
      $theme_info['template'] = $template;
      $theme_info['path'] = $fs->dirname($file->uri);
      $theme_info['base hook'] = $base_theme;
      $theme_info['type'] = 'module';
      $theme_info['theme path'] = $module_path;

      $theme_registry[$theme] = $theme_info;
    }
  }
}