I am using $form_state->setErrorByName() on a Webform element. Functionally everything works:
– The validation error is shown at the top of the page
– The specific element is marked as invalid
– The error message is displayed correctly

However, my dblog consistently reports a warning coming from FormState::getError():
foreach() argument must be of type array|object, null given
After investigating the implementation of getError(), I found that the problem occurs when $element['#parents'] is missing or NULL, which is common for Webform elements that do not have full Form API parent structures.

I tested a minimal defensive fix that prevents the warning in
/public_html/core/lib/Drupal/Core/Form/FormState.php:

  public function getError(array $element) {
    if ($errors = $this->getErrors()) {
      $parents = [];
+      $element_parents = $element['#parents'] ?? []; // <- Indsat af CBM 2026-09-11
-      foreach ($element['#parents'] as $parent) {
+      foreach ($element_parents as $parent) {
        $parents[] = $parent;
        $key = implode('][', $parents);
        if (isset($errors[$key])) {
          return $errors[$key];
        }
      }
    }
  }

This small change eliminates the dblog warning and allows setErrorByName() to work normally with Webform elements that do not provide a full #parents structure.

Would there be any problems or side effects if this defensive check were added to Drupal core?

Comments

uv516 created an issue. See original summary.

uv516’s picture

uv516 commented
Issue summary: View changes
cilefen’s picture

cilefen commented
Component: cron system » forms system
Category: Feature request » Bug report
Issue tags: -getError, -setErrorByName, -webform +Needs tests, +Needs steps to reproduce

As written, this seems to be a bug. Can we get the specific steps to reproduce this bug added to the issue summary?

cilefen’s picture

cilefen commented
Status: Active » Postponed (maintainer needs more info)
Related issues: +#3251855: PHP warnings when submitting a contact form with empty message, +#3116669: PHP Error messages when using image captcha

In these prior cases, the fixes were to the Webform module, so maybe only certain elements are affected.

uv516’s picture

uv516 commented

I have created a Webform and I am using hook_form_alter() to attach a custom validator:

$form['#validate'][] = '_webform_validate';

Inside _webform_validate(), I retrieve the submission entity using:

$submission = $form_state->getFormObject()->getEntity();

I then fetch a specific Webform element value:

$test = $submission->getElementData('myfield') ?? [];

The value is validated, and if an error is detected, I call:

$form_state->setErrorByName('myfield', $message);

Everything appears to work correctly:

  • The error message is shown at the top of the page
  • The affected field is highlighted
  • T

he link from the top error message scrolls correctly to the field

However, dblog consistently reports warnings coming from FormState::getError(), as described earlier.
The form behaves correctly, but the repeated foreach() warnings indicate that getError() is not handling Webform elements that lack a full Form API #parents structure.