Deprecated function: mb_strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\Component\Utility\Html::getId() (line 219 of core/lib/Drupal/Component/Utility/Html.php)

Problem/Motivation

For PHP 8.1, calling the mb_strtolower() function with a null argument returns a deprecation error:

Deprecated function: mb_strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\Component\Utility\Html::getId() (line 219 of core/lib/Drupal/Component/Utility/Html.php).
Drupal\Component\Utility\Html::getId(NULL) (Line: 121)
__TwigTemplate_fdec0ba362e0f13a146c27640b999ff1->doDisplay(Array, Array) (Line: 405)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 378)
Twig\Template->display(Array) (Line: 390)
Twig\Template->render(Array) (Line: 55)
twig_render_template('themes/citizen_patterns/templates/zzz-custom/widgets/00-base/field--node--field-paragraphs.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('field', Array) (Line: 422)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 201)
Drupal\Core\Render\Renderer->render(Array) (Line: 479)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 122)
__TwigTemplate_225f1ad20ce32204822f192356151c59->block_content(Array, Array) (Line: 182)
Twig\Template->displayBlock('content', Array, Array) (Line: 111)
__TwigTemplate_225f1ad20ce32204822f192356151c59->block_blockContent(Array, Array) (Line: 182)
Twig\Template->displayBlock('blockContent', Array, Array) (Line: 78)
__TwigTemplate_225f1ad20ce32204822f192356151c59->doDisplay(Array, Array) (Line: 405)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 378)
Twig\Template->display(Array) (Line: 390)
Twig\Template->render(Array) (Line: 55)
twig_render_template('themes/citizen_patterns/templates/zzz-custom/blocks/block--field-block.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('block', Array) (Line: 422)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 435)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 201)
Drupal\Core\Render\Renderer->render(Array) (Line: 479)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 97)
__TwigTemplate_1259748214d9a4428585fb011ef8998c->doDisplay(Array, Array) (Line: 405)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 378)
Twig\Template->display(Array) (Line: 390)
Twig\Template->render(Array) (Line: 55)
twig_render_template('themes/citizen_patterns/templates/zzz-custom/layout/layout--twocol-quad-split.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('layout__twocol_quad_split', Array) (Line: 422)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 201)
Drupal\Core\Render\Renderer->render(Array) (Line: 479)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 221)
__TwigTemplate_8e8ddbeacf22bec82b0db581af4be584->block_layoutSectionContent(Array, Array) (Line: 182)
Twig\Template->displayBlock('layoutSectionContent', Array, Array) (Line: 194)
__TwigTemplate_8e8ddbeacf22bec82b0db581af4be584->block_layoutSections(Array, Array) (Line: 182)
Twig\Template->displayBlock('layoutSections', Array, Array) (Line: 154)
__TwigTemplate_8e8ddbeacf22bec82b0db581af4be584->block_node(Array, Array) (Line: 182)
Twig\Template->displayBlock('node', Array, Array) (Line: 58)
__TwigTemplate_045d80dce83336544d39f3d671ded776->doDisplay(Array, Array) (Line: 405)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 378)
Twig\Template->display(Array, Array) (Line: 53)
__TwigTemplate_8e8ddbeacf22bec82b0db581af4be584->doDisplay(Array, Array) (Line: 405)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 378)
Twig\Template->display(Array) (Line: 390)
Twig\Template->render(Array) (Line: 55)
twig_render_template('themes/citizen_patterns/templates/zzz-custom/content/node.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('node', Array) (Line: 422)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 201)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 241)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 132)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 142)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 174)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

I'm not sure I can describe how to reproduce this error reliably but it seems to be related to the use of paragraphs. On the site I'm working on, if the page does not have a paragraph reference, no errors display. The error only shows on pages with paragraphs. Regardless of the cause, the variable needs to checked for a value prior to running any string functions on it.

Proposed resolution

Adding this snippet to line 219 of the web/core/lib/Drupal/Component/Utility/Html.php appears to remedy the problem:

  if (!$id) {
    return;
  }

or converting the code on line 219 to a ternary statement appears to work as well:

  $id = $id ? istr_replace([' ', '_', '[', ']'], ['-', '-', '-', ''], mb_strtolower($id)) : '';

Remaining tasks

Complete tasks from #11
Ensure all work identified by tags is complete
Hide all patches, we are using only MRs now.

User interface changes

API changes

Data model changes

Release notes snippet