Can't delete shipping methods if these were used in previous orders

[filipefurtad0]

Description

Observed while testing #6039

Currently, shipping methods can be:

• deactivated
• hidden from frontoffice i.e., set to backoffice only

This bug report relates to the fact that shipping methods currently cannot be deleted, despite the trash-bin icon on the page /admin/shipping_methods

This does work, if the shipment method has not been used in any order.

This issue is likely to be blocked two other issues, as deleting the shipping method will probably trigger the same issues as de-activating it, see below (taken from #5399 (comment)):

• and then editing a complete order that have not been shipped and is assigned to that shipping method, will automatically remove that shipping method from the order and assign another active shipping method Deactivating a shipping method with fees leads to wrong delivery method and payment status in previous orders #5367
• will make the shipping method disappear from the list of shipping methods (this one is applicable to payment methods as well) Shipping or payment method disappears from the list if you de-activate #4837

Expected Behavior

Deleting (previously used) shipment-methods is possible: the trash-bin symbol on the page /admin/shipping_methods works as expected.

Actual Behaviour

Deleting shipment-methods is not possible: the trash-bin symbol on the page /admin/shipping_methods does not work for previously used shipping methods.

Steps to Reproduce

As admin

1. Create two shipping methods, A and B
2. Create and ship an order, using shipping method A
3. Go to /admin/shipping_methods
4. Try to delete shipping method A and B by clicking on the respective trash-bin logos. See how they both disappear.
5. Refresh the page: shipping method A should be back on the screen; B should not.

Animated Gif/Screenshot

Workaround

As per comment below, The workaround is to deactivate the shipment method in the enterprise settings. But this can lead to other issues, as a consequence like:

#5367
#6029

Severity

I'm not sure on the severity here. I think the fact that this is currently not possible prevents greater damage...

Your Environment

• Version used: v3.2.8
• Browser name and version: Firefox 81
• Operating System and version (desktop or mobile): Desktop Ubuntu 20.04

Possible Fix

[audez]

Just to give some more input:
The workaround is to deactivate the shipment method in the enterprise settings (admin/enterprises/haha/edit#!/shipping_methods). When unchecking the box and clicking "update" button, the shipment method will be removed (unless it's also used by another enterprise for which no order has been made with it)
#4837

So it's possible and causes damages indeed:
#5367
#6029

[filipefurtad0]

Thanks for adding to this @audez 💪
I've updated the Workaround section with your findings.