Upgrading from v2 to v3 or v4 breaks preselection in `anyOf` schema

Prerequisites

• I have read the documentation;
• In the case of a bug report, I understand that providing a SSCCE example is tremendously useful to the maintainers.
• I’m providing a couple of sample sandboxes demonstrating the issue.

Description

I’m not sure this is technically a bug, as I haven’t found the broken behaviour documented anywhere. But it does work in v2, breaks in v3.0.0+ and I consider it an essential feature.

Here is a working v2.5.1. sandbox … and here is a sandbox with identical code, but broken, because it runs on v3.0.0.

Steps to Reproduce

1. Create an anyOf schema with two distinct types of anyOf items
2. Render a <Form> with this schema, and formData exclusively corresponding to the second schema item

Expected (v2.5.1.) behavior

Form renders with the second anyOf item selected - the item matched by formData

Actual (v3.0.0) behavior

Form always renders with the first anyOf item selected - regardless of formData not complying with the UI-selected schema

[michal-kurz]

@epicfaace I have no idea, I haven’t compared the code at all. But I suppose this part of migration docs might have something to do with it.

[andreySimonenko]

In this case it works on v2.5.1 because the list of enums has only one value. When we add more than one values in enum, default value also breaks.

@epicfaace I added a PR with test. Is there a way to fix this problem?