selected_variation also need to be set when Product has only one variation

Dave Kopecek → made their first commit to this issue’s fork.

This is necessary when selling custom product with a refresh price

Can you elaborate? "selected_variation" isn't set in this case because that is used by the ajax refresh callback, but there are no attributes elements in case of a single variation?

>> Can you elaborate? "selected_variation" isn't set in this case

In my use case we have a custom my_module_form_commerce_order_item_add_to_cart_form(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id that has:

    $vid = $form_state->get('selected_variation');
    $variation = \Drupal\commerce_product\Entity\ProductVariation::load($vid);

This broke when a new product with only a single variation was created. Is there a better way to get the current variation from the passed parameters?

I guess we can consider your fix but in the meantime you could just have a condition that checks if $form_state->has('selected_variation'); otherwise you can fallback to the first variation referenced from the product.

Does the attached patch help?