Ensure the latest revision of an order is loaded before checkout routing

Problem/Motivation

Seeing this issue during checkout:

EntityMetadataWrapperException: Missing data values. in EntityMetadataWrapper->value() (line 83 of /.../sites/all/modules/entity/includes/entity.wrapper.inc).

There are likely many other ways to reproduce this issue, but one sure fire way is as follows:

First, you need a drupal install that includes the following enabled modules.

• Commerce (all modules)
• Entity Registration
• Commerce Registraton
• Commerce Rules Extra

Steps to reproduce:

1. Create a registration enabled product (a product with a registration field attached).
2. Ensure that the registration settings for the product has the "Enabled" checkbox unchecked so that essentially registration is not available.
3. Create a new order through the order admin UI.
4. Add a line item for the disabled registration product.
5. Set the order status to "Checkout: Registration" and optionally choose an owner user for the order.
6. As the user that owns the order go to /checkout/
7. You should see the EntityMetadataWrapperException error.

The issue is not inherently Commerce, but the avenues Commerce has allowed through its hooks for an order to be manipulated during the order entity loading before the checkout routing process. In the example used to reproduce the issue it is the Commerce Rules Extra and Commerce Registration module that ultimately leads to the order becoming out of sync during the initial loading of the order for commerce_checkout_router().

When the drupal menu system first loads the order object to pass to commerce_checkout_router() there are various steps that occur, and the call stack can be summarized as follows:

• {{menu routing}} ->
• menu_get_object() ->
• commerce_order_load() ->
• commerce_cart_commerce_order_load() ->
• commerce_cart_order_is_cart("up to this point the order object has been passed along") ->
• commerce_order_statuses("order is not passed") ->
• {{order status hooks}} ->
• commerce_rules_extra_commerce_checkout_pane_info_alter() ->
• menu_get_object('commerce_order')
• ...

So in the last call shown above the commerce_rules_extra_commerce_checkout_pane_info_alter tries to get the order object again and at that point the order object loading process starts again and gets fullfilled and the commerce_order_load() -> commerce_cart_commerce_order_load() steps are called again and there are other hooks such as hook_commerce_cart_order_refresh() that allow the order object to be altered. Since this latter version of the order object is a newer revision and disconnected from the original that ultimately gets passed to commerce_checkout_router() the data is out of sync. In the example commerce registration has removed the line item for the registration product because it is not allowed to register to a product that is disabled. This results in the EntityMetadataWrapper to have a stale reference to a no longer existing line item and hence the Exception when trying to access it.

Wow, that totally sucked debugging that!

Proposed resolution

This isn't a commerce_registration issue because the point of hook_commerce_cart_order_refresh() is to be able to modify the order in the cart/checkout process.

This is kind of a commerce_rules_extra issue because it loads the order the second time, but really what else can it do at that point to give contextual data about the current order and I can't see a way around it.

So this brings us to the commerce_checkout_router() function. It doesn't make sense that you would ever want to use an order that is NOT the current revision during checkout so lets just add a check to make sure that the order passed to the function is indeed the latest and greatest. Problem solved!

Remaining tasks