Altering commerce invoice mails fails

Question

I'm altering different emails from my hook_mail_alter(&$message) function. But for some reason altering the email sent by commerce invoice module is not working. I'm trying to do it like:

switch($message['id']){
    case 'invoice_confirmation':
      $message['subject'] = 'Some other title';
      break;

I found the code that sends that email in invoice module:

  public function send(InvoiceInterface $invoice, $to = NULL, $bcc = NULL) {
    $to = isset($to) ? $to : $invoice->getEmail();
    if (!$to) {
      // The email should not be empty.
      return FALSE;
    }

    $subject = $this->t('Invoice #@number', ['@number' => $invoice->getInvoiceNumber()]);
    $body = [
      '#theme' => 'commerce_invoice_confirmation',
      '#invoice_entity' => $invoice,
      '#totals' => $this->invoiceTotalSummary->buildTotals($invoice),
    ];
    if ($billing_profile = $invoice->getBillingProfile()) {
      $body['#billing_information'] = $this->profileViewBuilder->view($billing_profile);
    }

    $params = [
      'id' => 'invoice_confirmation',
      'from' => $invoice->getStore()->getEmail(),
      'bcc' => $bcc,
      'invoice' => $invoice,
    ];
    $customer = $invoice->getCustomer();
    if ($customer->isAuthenticated()) {
      $params['langcode'] = $customer->getPreferredLangcode();
    }
    $file = $this->invoiceFileManager->getInvoiceFile($invoice);
    $attachment = [
      'filepath' => $file->getFileUri(),
      'filename' => $file->getFilename(),
      'filemime' => $file->getMimeType(),
    ];
    $params['attachments'][] = $attachment;

    return $this->mailHandler->sendMail($to, $subject, $body, $params);
  }

}

and there I saw that id should be 'invoice_confirmation', but like my hook function is never reached when this email is sent?! How to alter this email title?

Answer 1

Solved the issue - id is actually 'commerce_invoice_confirmation'.

I was trying to print out $message['id'] and stop executing of code, but that never happened? So I assumed that my code was never called. Not sure why. So I used watchdog logger to log id value and found it out.