Trying to populate a ticket with values from the associated product - devel shows no data in the fields?

Is anyone able to suggest a route forward ?

I still need to be able to allow a user to add values to a ticket on purchase.
I have tried to to use ECA but don't seem able to trigger a response to the checkout event at pre-save.

Would https://www.drupal.org/project/field_inheritance → be a plausible way inheriting the details from the product onto the ticket?

So I have eventually managed to get this working. Going to dump a number of things here in the hope that it helps someone and hopefully becomes somewhat of a reference. Am sure there would have been easier/better ways, but I am far from a developer!

Firstly the end result:

To get a working D10 install:

Follow the instructions here : https://www.drupal.org/project/commerce_ticketing/issues/3382034#comment... ✨ Drupal 10 upgrade RTBC (note the repo comments that follow)
In addition, I have these patches:

"drupal/entity_print": {
                "3383187 - Unexpected Error, Session has not been set": "https://www.drupal.org/files/issues/2023-12-06/3383187-5.patch"
            },
"drupal/commerce_ticketing": {
                "3416185 - symphony mailer plugin": "https://git.drupalcode.org/project/commerce_ticketing/-/merge_requests/29.diff",
                "3415783 - tickets not autosending": "https://www.drupal.org/files/issues/2024-03-13/autoactivating-3415783-12.patch",
                "3425570 - Error: Call to a member function getWorkflowId() on null": "https://www.drupal.org/files/issues/2024-03-05/commerce_ticketing-3425570.patch",
                "3250757 - Events and Disabled Tickets": "https://www.drupal.org/files/issues/2024-03-12/events-disabled-tickets-3250757-8.patch",
                "3415300 - ticketing twig theming patch": "https://www.drupal.org/files/issues/2024-01-17/theming-3415300-4.patch"

Rather than store additional details in a field on the ticket entity (although I tried!) I ended up using a pre-process function in my own module to make the values I needed available on screen, and when printing.

For me they are:
- details from the product (that sold the ticket)
- details from the event that the product was related to (I am using https://www.drupal.org/project/recurring_events → for events), all products based on ticket type 'event ticket' have required field, that is an entity reference to an event instance.
- details from the account / user that transacted the ticket.

In my module I implement:

/**
 * Implements hook_preprocess_HOOK() for commerce_ticket templates.
 *
 * Enhances the ticket template with detailed information including:
 * - Ticket specifics such as type and associated product details.
 * - Ownership details based on ticket assignments.
 * - Customer information derived from the order, prioritizing billing profile data with fallbacks to user data.
 * - Event details linked through the product variation.
 *
 * @param array &$variables
 *   The variables array passed to the ticket template.
 */
function geminigames_tickets_mod_preprocess_commerce_ticket(&$variables) {
// Extract the ticket entity from the render array.
$ticket = $variables['elements']['#commerce_ticket'];

if ($ticket) {
  // Pass the ticket entity itself to the Twig template for debugging or other uses.
  $variables['ticket'] = $ticket;

  // Extract and pass the machine name of the ticket type to the template.
  $variables['ticket_type'] = $ticket->bundle();

  // Extract and pass the plaintext version of the ticket number to the template.
  // Check if the ticket has a 'ticket_number' field and it has a value.
  if ($ticket->hasField('ticket_number') && !$ticket->get('ticket_number')->isEmpty()) {
      // Extract the ticket number value.
      $variables['plain_ticket_number'] = $ticket->get('ticket_number')->value;
  }
    // Extract and pass the ticket status to the template.
    // Check if the ticket has a 'state' field and it has a value.
    if ($ticket->hasField('state') && !$ticket->get('state')->isEmpty()) {
      // Extract the ticket status value.
      $variables['ticket_status'] = $ticket->get('state')->value;
  }
  if (isset($variables['content']['entity_print_view_pdf'])) {
    // Change the link text.
    $variables['content']['entity_print_view_pdf']['#title'] = t('here');
}
}

  // Extract associated product details from the ticket's order item.
  if ($order_item = $ticket->getOrderItem()) {
      $product_variation = $order_item->getPurchasedEntity();
      if ($product_variation) {
          $product = $product_variation->getProduct(); // Associated product entity.
          $variables['product_title'] = $product->getTitle();
          $variables['product_variation_title'] = $product_variation->getTitle();
      }
  }

  // Set details for the ticket's owner.
  $owner = $ticket->getOwner();
  if ($owner) {
      $variables['ticket_owner_name'] = $owner->getDisplayName();
  }

  // Extract and process customer information from the associated order.
  $order = $ticket->getOrder();
  if ($order) {
      $customer_user = $order->getCustomer(); // User entity associated with the order.
      // Set customer's email from the user entity associated with the order.
      $variables['customer_email'] = $customer_user->getEmail();

      // Initialize customer information variables.
      $customer_name = $customer_first_name = $customer_last_name = t('Not available');

      // Attempt to extract name information from the billing profile's address field.
      $billing_profile = $order->getBillingProfile();
      if ($billing_profile && $billing_profile->hasField('address')) {
          $address = $billing_profile->get('address')->first();
          if ($address) {
              $customer_first_name = $address->getGivenName();
              $customer_last_name = $address->getFamilyName();
              $customer_name = $customer_first_name . ' ' . $customer_last_name;
          }
      }

      // Use user entity as fallback for names if not populated from billing profile.
      if ($customer_first_name == t('Not available') || $customer_last_name == t('Not available')) {
          $customer_name = $customer_user->getDisplayName();
      }

      // Set finalized customer details in variables.
      $variables['customer_name'] = $customer_name;
      $variables['customer_first_name'] = $customer_first_name;
      $variables['customer_last_name'] = $customer_last_name;
  }

  // Retrieve and set event details linked to the product variation.
  if (isset($product_variation) && $product_variation->hasField('field_associated_event') && !$product_variation->get('field_associated_event')->isEmpty()) {
      $event = $product_variation->get('field_associated_event')->entity;
      if ($event) {
          // Assuming 'date' is a Daterange field containing event start and end times.
          $start_date = $event->get('date')->start_date;
          $end_date = $event->get('date')->end_date;

          // Set event details for the template.
          $variables['event_title'] = $event->label();
          $variables['event_start_date'] = $start_date->format('Y-m-d');
          $variables['event_start_time'] = $start_date->format('H:i');
          $variables['event_end_date'] = $end_date->format('Y-m-d');
          $variables['event_end_time'] = $end_date->format('H:i');
      }
  }

  // Retrieve the active theme's settings.
  $theme = \Drupal::theme()->getActiveTheme()->getName();
  $theme_settings = \Drupal::config('system.theme')->get('default');
  $logo_path = theme_get_setting('logo.url', $theme);

  // Check if a custom logo has been set for the theme.
  if (!empty($logo_path)) {
      // Pass the logo URL to the template.
      $variables['theme_logo'] = $logo_path;
  }

}

My twig file, then looks like this:

<div class="container mt-4">
  <div class="row">
    <div class="col">
      <div class="alert alert-info" role="alert">
        <h4 class="alert-heading">Ticket Information</h4>
        {% if event_title %}<p>Please find on this page your ticket for <strong> {{ event_title }}</strong> on <strong> {{ event_start_date }}</strong>.{% endif %}
        {% if not event_title %}<p>Please find on this page your ticket for <strong> {{ product_title }}</strong>.{% endif %}
        Please check your details and get in touch with Gemini Games if this information appears incorrect.</p>
        <p class="muted">{{ 'This ticket @ticket_number, was generated by order #@number.'|t({'@ticket_number': commerce_ticket.getTicketNumber, '@number': order.getOrderNumber}) }}</p>
        <hr>
        <p class="mb-0">- The status of your ticket is: <strong> {{ ticket_status }}</strong></p>
        <p class="mb-0">- Your ticket number is: <strong> {{ plain_ticket_number }}</strong></p>
          {% if content.entity_print_view_pdf %}
  <p class="mb-0 d-inline">
    - You can download your PDF of this ticket
    <a href="{{ content.entity_print_view_pdf['#url'] }}" class="alert-link">here</a>.
  </p>
{% endif %}


      </div>
    </div>
  </div>
</div>

<div class="row justify-content-center">
  <div class="col-lg-8 col-md-10">
    <div class="card mb-3 border border-4 border-dark">
      <div class="row g-0">
        <!-- Left Column: QR Code and Logo -->
        <div class="col-md-5 col-lg-4 bg-primary p-3 d-flex flex-column align-items-center justify-content-center">
          <div class="qr-container bg-white p-1 mb-3" style="border: 4px solid black; max-width: 220px;">
            {% if content.qr_code %}
              <div class="ticket-qr-code" style="width: 100%; height: auto;">{{ content.qr_code }}</div>
            {% endif %}
          </div>
          <!-- Theme Logo below QR Code -->
          {% if theme_logo %}
            <img src="{{ theme_logo }}" class="img-fluid mb-3" alt="Theme Logo">
          {% endif %}
        </div>

        <!-- Right Column: Product, Ticket and Event Details -->
        <div class="col-md-7 col-lg-8 bg-light p-4">
          <div class="card-body">
            <!-- Product Title -->
            <div class="row mb-4">
              <div class="col">
                <h4 class="display-6">{{ product_title }}</h4> <!-- Larger title font -->
              </div>
            </div>

            <!-- Ticket Details -->
            <div class="row mb-4">
              <div class="col">
                <h5 class="card-title fw-bold">Ticket Details</h5> <!-- Ticket details heading -->
                <p class="card-text">
                  <strong>Ticket Type:</strong> {{ product_variation_title }}<br>
                  <strong>Ticket Number:</strong> {{ plain_ticket_number }}<br>
                  <strong>Customer Name:</strong> {{ customer_name }}<br>
                  <strong>Customer Email:</strong> {{ customer_email }}
                </p>
              </div>
            </div>

            <!-- Event Details, displayed only if there is an event title -->
            {% if event_title %}
              <div class="row">
                <div class="col">
                  <h5 class="card-title fw-bold">Event Details</h5> <!-- Event details heading -->
                  <p class="card-text">
                    <strong>Event Title:</strong> {{ event_title }}<br>
                    <strong>Event Date:</strong> {{ event_start_date }}<br>
                    <strong>Event Time:</strong> {{ event_start_time }}
                  </p>
                </div>
              </div>
            {% endif %}
          </div>
        </div>
      </div>
    </div>
  </div>
</div>

Hopefully there is enough here to help someone!

I don't think any of this is contributable / patchable without a D10 release ?

Id love to know some next steps to progress - I need to put this into production fully, but am getting composer issues with:

mizpah@Asborian:~/development/gemini-gaming-production$ composer status -v
> command: Drupal\Composer\Plugin\Scaffold\Plugin->onCommand
You have changes in the following dependencies:
web/modules/contrib/commerce_ticketing:
    M commerce_ticketing.install
    M commerce_ticketing.module
    M config/install/commerce_product.commerce_product_variation_type.ticket.yml
    M config/schema/commerce_ticketing.schema.yml
    M src/CommerceTicketCreateTickets.php
    M src/CommerceTicketListBuilder.php
    M src/CommerceTicketRouteProvider.php
    M src/Entity/CommerceTicket.php
    M src/EventSubscriber/OrderEventSubscriber.php
    M tests/src/Kernel/TicketCreationTest.php
    M tests/src/Kernel/TicketKernelTestBase.php

I should note that everything is working - but am not really sure on next steps.

what need to happen to make a 'normal' D10 version of the module?