Gen2 Package, ancestor version creation failing without any code changes for 2GP Managed package

Question

I have the following issue with the Second Generation Package, I have this Apex class:

global with sharing class TestClass {
    global virtual class B {
    }
    global class C1 extends B {
    }
    global class C2 extends B {
    }
}

On the foobarbaz namespace, in a managed package, I upload and release a first managed version (v1.0.0) and then, without changing any code at all, I try to create a new minor version (v1.1.0) that have for ancestor the v1.0.0 but I'm getting the following error when I try to create the version:

TestClass: Supertype, foobarbaz.TestClass, relationship must be maintained: foobarbaz.TestClass.C1,TestClass: Supertype, foobarbaz.TestClass, relationship must be maintained: foobarbaz.TestClass.C2

I tested creating a minor version without changing the code source with the First Generation Package, and it's working fine.

So, what's the issue there?

Edit: Here's a Minimium Reproducible Case repository https://github.com/louis-bompart/sturdy-funicular

It's a simple sfdx project setup with sfdx-cli and the aforementioned Apex class. The first commit is the first release (v1.0.0) The second commit is the second attempted release. (v1.1.0)

Edit2: The ancestory tree: https://docs.google.com/drawings/d/10bbSnR5wB1mgfuGNJ3fz_YLEYC-ahevnjqbmZyHECDw/edit?usp=sharing Here's some more elaborated steps on how to reproduce: After the package is created, but no version exists yet:

• sfdx force:package:version:create -p FooBazBar -v mydevhub@foo.com -x -c
• sfdx force:package:version:promote --package 04tmypackageid -v mydevhub@foo.com
• Update sfdx-project.json by adding "ancestorVersion": "0.1.0.1" in the only packageDirectory
• sfdx force:package:version:create -p FooBazBar -v mydevhub@foo.com -x -c
• Crash

Answer 1

This is been brought to the attention of Salesforce Managed Package team and a bug is raised against this with Internal work item number W-7503352.

Please reference this if you ever raise a support case for this.

There is a known issue created for this now. Please follow for updates.