Warning: Undefined array key "form_alter" in Drupal\symfony_mailer\MailerHelper->formAlter() (line 211 of modules/contrib/symfony_mailer/src/MailerHelper.php).

Attached a patch

Tried module with version 1.3.1, and the issue is not reproducible by accessing the pages admin/reports/updates or /node/add/article . Please add some more steps that was used to reproduce the issue.

I have fixed this issue Undefined array key "form_alter"

I agree with #3 - this needs steps to reproduce. \Drupal\symfony_mailer\Annotation\EmailBuilder sets $form_alter = [] so how can it be undefined?

@AdamPS I don't get how $this->formAlter = []; would help $definition['form_alter']

However I can't replicate anymore - I suspect this warning was in relationship with some other contrib module, as I updated a lot of them after this report.

Therefore sorry for your time, I'm going to close this issue.

Khalid Ansari → made their first commit to this issue’s fork.

I encountered the identical problem, which emerged from my attempt to modify the Drupal Commerce email builder class via hook_mailer_builder_info_alter. hook

In my custom module replaced $email_builders['commerce']['class'] with $email_builders['commerce_order_type']['class']

/**
 * Implements hook_mailer_builder_info_alter().
 */
function CUSTOM_MODULE_mailer_builder_info_alter(array &$email_builders) {
  $email_builders['commerce']['class'] = 'Drupal\CUSTOM_MODULE\Plugin\EmailBuilder\LegacyEmailBuilder';
  $email_builders['commerce_order_type']['class'] = 'Drupal\CUSTOM_MODULE\Plugin\EmailBuilder\LegacyEmailBuilder';
}