Xcode 12.2 & Big Sur: Source editor extensions have vanished

Thanks @satcol's sharing. I confirm that linking and embedding XcodeKit framework in the extension target works.

@satcol, could you please share the exact details of how you linked the XcodeKit lib?

I've added XcodeKit as a linked binary under Build Phases but when I link, it gives a linker error: "framework not found XcodeKit".

I can answer my own question about embedding and signing XcodeKit. I had my project selected instead of the target extension.

Steps to link XcodeKit (just in case someone else needs exact steps):

1. Select your top-level project in the Project Navigator.

2. Under TARGETS, select your extension to see its settings.

3. In the General tab, scroll down to Frameworks and Libraries.

4. For a new extension, it will show two libs: 1) Cocoa.framework; 2) XcodeKit.framework. Both have the option Do Not Embed selected.

5. Change XcodeKit.framework to Embed & Sign.

6. Rebuild.

I can also confirm this resolved the issue.

The strangest thing now happened. The extensions that worked a day ago no longer work. They are not even there when I open System Preferences > Extensions. It is as if it never existed. There was no reboot through the night, my macBook was closed.

How can this be? Nothing that I tried (even reboot) is helping. I can even create a new project and follow the steps to create an extension but not even debugging works (it starts debugging but the extension is not under the Editor menu in xcode.

Any suggestions?