Checkout complete page redirects to empty cart

thanks for taking the time to report this.

@RandomNeighbour I can not reproduce the issue. did you check this does not happen also without stocvk on your site?

I'm having this error, it happens when you only have one quantity in stock of some product. When you select Pay and complete the purchase, redirect to the shopping cart.

Location: /checkout/61/complete
Referring: /checkout/61/review

RuntimeException: Failed to start the session because headers have already been sent by vendor/symfony/http-foundation/Response.php" at line 1286. Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 141 /vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php)

This happens with me also. If you have stock 1 in cart , then on checkout complete it redirects to cart.

We experience the same issue. ( we have enabled commerce_stock_enforcement)

For example;

There is a product with 3 items in stock. 2 people are trying to buy the product twice. So only 1 succeed and the sock level will drop to 1. The other customer gets a message that he only can buy 1 item. If he proceed to buy that 1 item, the checkout flow is redirecting him to an empty cart.

--edit

An other use case:
2 items are in stock. 1 customer buys last 2 items. After buying the 2 items, the user is redirected to the empty cart page. Not to the thank you page.

Can this issue be related to the technical effect of: "Commerce stock enforcement not properly mapping cart rows to order items" ?

So commerce thinks the user is still busy with the cart?

edit--
not relevant anymore

This problem occurs when you have activated "Reserve stock on order complete" in the stock configuration.

Can confirm the behavior when the following is true:

1. Stock level for product variation is = 1
2. "Reserve stock on order complete" is active

If either of the above is not true then the checkout works as expected, i.e. I see the order complete page.

I am facing the same issue, confirmed the behaviour described by #11 and #12.

The stock gets recalculated after the order completion.
The Problem is in the form_alter of the enforcement module, which checks the the stock on each form build and there for as well in the last pane when the order already has been completed. At this point the stock is not already reduced and therefore the validaten will fail, resulting in the redirect.

#14 The patch works for me, thanks @Siegrist

Nice one Siegrist!

Added new patch where directory structure match module directory structure.

Thanks Siegrist and Martijn de WIt! Patch in #16 worked for me as well

Let's set this to reviewed by community with several +1's :)

Big thanks to everyone who helped.
@jwwj followed your instructions and was able to recreate.
@Siegrist - Reading your explanation made it all make sense.
@Martijn de Wit - thanks for helping to push this. It does help to c the "Reviewed & tested by the community" :)

#16 is work for me. thanks.

The issue still happen on some situations.
For example if you enable the "Email registration guest registration after checkout" checkout flow pane, when you are purchasing a product with stock level 1, once you try to register you will experiment the following behavior:

• you won't be registered
• you will be redirected to the cart page
• you will see the error message "One or more Items are out of stock. Checkout canceled!".

Here is a patch fixing the issue. Can a maintainer review it? thanks a lot.

I can't reopen this issue because I'm not a maintainer, so I will create a new one.

I created a child issue and attached a new patch there

child issue was committed a while back so marking as fixed.