Optional objects validation regression in v3

[ifeltsweet]

Sanity Studio v3 has a regression from v2 for https://github.com/sanity-io/sanity/issues/2630.

Specifically, optional empty objects once touched are not unset, even if all nested fields are empty, thus making all nested validations fail.

To Reproduce

Steps to reproduce the behavior:

1. Create a simple schema with an optional object that has a required nested field.

   {
   title: 'Test',
   name: 'test',
   type: 'document',
   fields: [
   {
     type: 'object',
     name: 'Object',
     fields: [
       {
         type: 'text',
         name: 'nested',
         validation: (Rule) => Rule.required(),
       },
     ],
   },
   ],
   }

2. Edit the nested field.

3. Empty the nested field.

4. Observe that now you are unable to publish the document because nested field validation fails.

Expected behavior

In step 4 the validation should not fail as the whole object should be unset once all nested fields are empty.

Which versions of Sanity are you using?

3.2.6

[coreyward]

I can confirm this is happening for me as well in v3.2.5. The _type property on the object remains even after the last field is cleared.

[alexander-young]

We are having the same issue. It really messes things up when you use Zod when we'd need to expect undefined, an empty object, or the filled object

[gpoole]

This issue appears to be fixed at least as of 3.49.0 which is the version I tested on. Setting and unsetting a field on an optional object seems to behave as expected. Is that right @ifeltsweet?