Add an exception/warning/assert/other when a #options value is overriden because #empty_options

Hi,
We can add '#description' property as condition if we have '#empty_option' property in the form. This will conditionally render the description below the form field. Refer the example given below:-

/**
* {@inheritdoc}
*/
public function buildForm(array $form, FormStateInterface $form_state): array {

$form['select_element'] = [
'#type' => 'select',
'#options' => [
0 => 'zero',
1 => 'one',
2 => 'two'
],
'#required' => TRUE,
'#empty_value' => TRUE,
'#empty_option' => "Some empty value"
];
if($form['select_element']['#empty_option']) {
$form['select_element']['#description'] = 'Empty option present will replace the option.';
}
$form['actions'] = [
'#type' => 'actions',
'submit' => [
'#type' => 'submit',
'#value' => $this->t('Send'),
],
];

return $form;
}

Could be an option to solve this but it has to be implemented on the element level. However, adding a text to the description could be not enough (maybe the text is hidden and devs won't see it). I would say to set a drupal warning message instead.

Hi,
I have created a patch which displays a warning, when $form['#empty_value'] exist in the form and is set to 1 as I saw that the $form['#empty_option'] replaces the $form['#option'] only when $form['#empty_value'] is set to 1. Please review the patch.

Fixed failures in #5.