Mrthdrb

I am referring to question -
how to add custom data in order email in magento 2

Below is by observer execute method

public function execute(MagentoFrameworkEventObserver $observer)

 /** @var MagentoFrameworkAppActionAction $controller */
 $transport = $observer->getTransport();
 $transport['businessname'] = "XYZ";

Below is my event.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
 <event name="email_invoice_set_template_vars_before">
 <observer name="custom_invoice_email_variable" instance="VendorNameModuleNameObserverSalesInvoiceTemplateVarsBefore" />
 </event>
</config>

I am calling it in a template as - raw . But still I am not getting it in the email template. I checked by putting logs in observer and my observer method is getting called, But the variable is not get set and not shown in invoice template.

Please help.

Its a bug of magento as wrote in the comment of your question.

I resolved the problem in this way (but I changed order comments email vars, but use same changes for invoice core classes):

1) I created preference class for core class because it bad way write code in core file.
- added in di.xml code

 <preference for="MagentoSalesModelOrderEmailSenderOrderCommentSender" type="NamespaceExtensionNameModelOrderEmailSenderOrderCommentSender" />

2) Fixed source code in my class. The main idea: we added prepareTemplate and we need extend source MagentoSalesModelOrderEmailSenderOrderCommentSender to prevent another core error.

<?php
 /**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
 namespace SfdevSecretDeliveryModelOrderEmailSender;

 use MagentoFrameworkOauthException;
 use MagentoSalesModelOrder;
 use MagentoSalesModelOrderEmailContainerOrderCommentIdentity;
 use MagentoSalesModelOrderEmailContainerTemplate;
 use MagentoSalesModelOrderEmailNotifySender;
 use MagentoSalesModelOrderAddressRenderer;
 use MagentoFrameworkEventManagerInterface;

 /**
 * Class OrderCommentSender
 */
 class OrderCommentSender extends **MagentoSalesModelOrderEmailSenderOrderCommentSender**
 
 /**
 * @var Renderer
 */
 protected $addressRenderer;

 /**
 * Application Event Dispatcher
 *
 * @var ManagerInterface
 */
 protected $eventManager;

 **public $comment = '';**

 /**
 * @param Template $templateContainer
 * @param OrderCommentIdentity $identityContainer
 * @param OrderEmailSenderBuilderFactory $senderBuilderFactory
 * @param PsrLogLoggerInterface $logger
 * @param Renderer $addressRenderer
 * @param ManagerInterface $eventManager
 */
 public function __construct(
 Template $templateContainer,
 OrderCommentIdentity $identityContainer,
 MagentoSalesModelOrderEmailSenderBuilderFactory $senderBuilderFactory,
 PsrLogLoggerInterface $logger,
 Renderer $addressRenderer,
 ManagerInterface $eventManager
 ) 
 parent::__construct($templateContainer, $identityContainer, $senderBuilderFactory, $logger, $addressRenderer, $eventManager);
 $this->addressRenderer = $addressRenderer;
 $this->eventManager = $eventManager;
 

 /**
 * Send email to customer
 *
 * @param Order $order
 * @param bool $notify
 * @param string $comment
 * @return bool
 */
 public function send(Order $order, $notify = true, $comment = '')
 
 **$this->comment = $comment;**
 return $this->checkAndSend($order, $notify);
 

 /**
 * Prepare email template with variables
 *
 * @param Order $order
 * @return void
 */
 **protected function prepareTemplate(Order $order)**
 
 $transport = [
 'order' => $order,
 'comment' => $this->comment,
 'billing' => $order->getBillingAddress(),
 'store' => $order->getStore(),
 'formattedShippingAddress' => $this->getFormattedShippingAddress($order),
 'formattedBillingAddress' => $this->getFormattedBillingAddress($order),
 ];
 $transport = new MagentoFrameworkDataObject($transport);

 $this->eventManager->dispatch(
 'email_order_comment_set_template_vars_before',
 ['sender' => $this, 'transport' => $transport]
 );

 try 
 $this->templateContainer->setTemplateVars($transport->getData());

 parent::prepareTemplate($order);
 catch (Exception $e) 

 $this->logger->error('ERROR EMAIL VARS');
 $this->logger->error($e->getMessage());
 

 

 

3) The result is - we can use core dispatch 'email_order_comment_set_template_vars_before' - it is working correctly

The problem is that you are not calling the right event.
It should be:

<event name="email_order_set_template_vars_before">

I think the event you are observing is when you are sending email by "Asynchronous sending".