Sylius: Exception when trying to add to cart a non found variant

[crevillo]

Here are the steps to reproduce this issue.

• Do a fresh install of beta1
• Go to the admin backend
• Create a new configurable product with "Mug Type" as only option and "Options Matching" as Variant Selected Method.
• Create a only variant for this product. Set "Medium mug" as "Mug Type" option
• Now go to the frontend page of the product you have created
• You will see the possibly option values for the mug type.
• If you try to add "medium mug" everything works as expected
• If you try to add the "monster mug" a exception is thrown that can be seen in the symfony profiler. it reads Expected argument of type "lius\Component\Core\Model\OrderItem::setVariant() must implement interface Sylius\Component\Core\Model\ProductVariantInterface", "NULL" given

Looks to me that we need to control if we have found a match before trying to add the item to the cart.

[David-Guillot]

This one will need 2 fixes:

• On UI side: when you select a variant that doesn't exist for a product, the text "Unavailable" is displayed instead of the price ; this means there is a JS event that could be used to also disable the "Add to cart" button and prevent the form to be submitted
• On PHP side: to prevent errors to be returned to the final user (through UI or API), the exception needs to be caught and handled properly

I'll try to work on these fixes today.