Recent changes to the way count_on_hand is summed in Spree::Stock::Quantifier mean the old method here will not work. Error:
```
2) Spree::Variant#in_stock? when stock_items are not backorderable when stock_items out of stock return false if stock_items out of stock
Failure/Error: expect(variant.in_stock?).to be_falsy
expected: falsey value
got: true
# ./spec/models/spree/variant_spec.rb:241:in `block (5 levels) in <module:Spree>'
```
Fixes an issue where a product's variant_unit value is changed from "weight" to "items" and some of the product's variants can be left in an invalid state, which in turn breaks cloning of order cycles (with fatal errors).
Note that, as explained in
https://apidock.com/rails/v3.2.13/ActiveRecord/Relation/delete, `delete` does
not trigger callbacks and so it skips the products cache logic.
If we still want to avoid instantiating the AR object, we need to explicitly
call that logic for the cache to be up-to-date.
Spree made that scope default so that we don't need to define or call
it. There might be cases in which we were showing deleted variants and
now we are not, but I have not idea how to find them.
Related Spree commit:
- cd3add960e
This keeps the override of Spree's model leaner. More importantly, it
prepares us for using `destroy` instead of `delete`.
In the past, `Product#delete` soft-deleted the product, but didn't
delete the variants. When we use `Product#destroy` to soft-delete the
product, it will also call destroy on the variants. If the model doesn't
allow the deletion of the last variant, it will fail. So when a product
is deleted we want to allow the deletion of all variants. But the user
should not be allowed to delete the last variant. That's why I'm moving
the check to the controller level.
Related commits:
- e6c7acdff3
- 2b47c9145a
- b9f19d5777 (diff-412c5af2ec1ba9f6643f6df5a673c1d4R105)
This makes the upgrade to Spree 2.0 a bit easier.
`spree_variants.count_on_hand` is removed in that version and this
column was used in the `in_stock` scope that we no longer use.
