Commerce product variation fields missing

Problem/Motivation

Product variations fields are not rendered on product when using DS

Steps to reproduce

Create a product type with variations. Create a product of that type and add a variation. In Manage Display for the product variation type, ensure some fields are enabled, e.g. Price.

In Manage Display for the product type, leave the layout for the product set to "None". Enable the virtual field "Variations" and choose "Add to Cart Form" as the formatter. When viewing the product you should see a Variations field with a dropdown to select the variation, and also the set of variation fields. (If there are multiple variations, changing the dropdown causes the fields to update).

Go back to Manage Display for the product type, and set the layout to something other than "None", e.g. "Two column". Then view the product again. The variations dropdown is still there but all the other fields pertaining to the variation have vanished.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes