When validating an options form for a views field plugin class that extends FieldPluginBase, you need to add a `validateOptionsForm()` function and use an array for getting the value although when setting the error you don't need to include 'options':/** * {@inheritdoc} */public function validateOptionsForm(&$form, FormStateInterface $form_state): void { parent::validateOptionsForm($form, $form_state); // Ensure that an Aria label is filled in if the button label is displayed. if ($form_state->getValue(['options', 'button_label_visibility']) && empty($form_state->getValue(['options', 'aria_label']))) { $form_state->setError($form['aria_label'], nt('Aria label is required when the button label is shown.')); }}
Note, I found that using $form_state->setErrorByName did not work for me, so I used setError() instead.