Applying percentage discounts when the line item data structure doesn't exist

Thanks for the patch, seems to solve our issue.

+++ commerce_discount.rules.inc
@@ -173,9 +173,11 @@ function commerce_discount_percentage(EntityDrupalWrapper $wrapper, $discount_na
-        if (!empty($line_item_types[$line_item_wrapper->type->value()])) {
...
+        if ($line_item_wrapper->value()) {
+          if (!empty($line_item_types[$line_item_wrapper->type->value()])) {

I did a quick check around commerce and other commerce modules to see how this is used and usually it's like this:

if (in_array($line_item_wrapper->type->value(), commerce_product_line_item_types())) {

So I'm guessing there is a deeper problem here, or this needs to change in most of the other modules including commerce core.

At the very least you could do what commerce_shipping does and put both conditions in the same if statement.

eg:

if ($line_item_wrapper->value() && !empty($line_item_types[$line_item_wrapper->type->value()])) {

What do you think?

Use a try/catch block instead of testing for individual values. So the example above becomes

try {
  if (!empty($line_item_types[$line_item_wrapper->type->value()])) { ... }
}
catch (Exception $e) {
  // No line item type found, do something else?
  continue;
}

@kscheirer what about

  if (!empty($line_item_types[$line_item_wrapper->getBundle()])) {

And that bigger problem I mentioned in #3 I think may be commerce_entitycache related.

@scotthooker could you try this patch out? #2538812: When discounts are deleted on existing carts I hope it resolves your problem as well as they are very similar.

Postponing until we can see if #2538812: When discounts are deleted on existing carts resolved the issue reported in summary.

Patch in #1 doesn't match reported error of Unable to get the data property commerce_unit_price as the parent data structure is not set. in EntityStructureWrapper->getPropertyValue(). It does work around the total.

Closing to triage the issue queue, reopen if you feel this still needs to be addressed.

If this is re-opened we need to add a test to ensure this issue doesn't re-surface.

I am having the same problem. Although doing this:

function commerce_discount_commerce_cart_order_pre_refresh($order) {
  $order_wrapper = entity_metadata_wrapper('commerce_order', $order);
  $discount_types = commerce_discount_types();
  $discount_types = array_keys($discount_types);
  foreach ($order_wrapper->commerce_line_items as $line_item_wrapper) {
    // NEW CODE ----
    if (!$line_item_wrapper->value()) {
      continue;
    }
    // -----

    $changed = commerce_discount_remove_discount_components($line_item_wrapper->commerce_unit_price, $discount_types);
    $changed = $changed || commerce_discount_remove_discount_components($line_item_wrapper->commerce_total, $discount_types);
    if ($changed) {
      $line_item_wrapper->save();
    }
  }
  if (isset($order_wrapper->commerce_order_total)) {
    $changed = commerce_discount_remove_discount_components($order_wrapper->commerce_order_total, $discount_types);
    if ($changed) {
      $order_wrapper->save();
    }
  }
}

Is supressing the exception, still I am trying to figure out why an empty line item is created in the first place.

Steps to reproduce:
- Create an order discount coupon
- Apply that coupon during checkout
- Refresh the checkout page
- You will see

EntityMetadataWrapperException: Unable to get the data property commerce_unit_price as the parent data structure is not set. in EntityStructureWrapper->getPropertyValue() (line 457)

And mysteriously a new null line item is created everytime you refersh the checkout page.

After much debugging I found that it is happening because commerce_shipping adds a line item, and then deletes it. There are commerce_shipping rules which does that. I tried altering the weights of those rules and the discount rule, but it is not working.

Since, the order update causes causes commerce_discount_commerce_cart_order_pre_refresh() to invoke, therefore, altering the priority of the rules is not going to work.

This is the patch that should fix the issue.

@subhojit777 Does that mean that we need commerce_shipping to reproduce the bug? I tried the steps in #9 but everything seemed to be fine, even with commerce_shipping enabled. I have the coupon redeem form on the first checkout step. Can you provide step-by-step instructions on how to reproduce this on a clean drupal site?

Yes you need commerce_shipping to see the error. I have set breakpoints in the code and found that commerce_shipping add and later removes a line item. And commerce_discount getting a null line item throws. I saw this error in an existing site. I will try to reproduce the error on a fresh setup.