In Flutter 3.3, source code for some SDK libraries (that were available in Flutter 3.0) appear missing when running on Windows.

To reproduce:

• Create a new Flutter counter app
• Add assert(false) into the incrementCounter function
• Run the app with Windows as the target
• Ensure debug settings are set to include SDK libraries (in VS Code this can be done by clicking on "Debug my code" in the status bar and toggling it to "Debug my code + sdk + packages")
• Click on the FAB button to trigger the assert

When using Flutter 3.0, you will break inside the source for dart:core/errors_patch.dart:

But when doing the same on Flutter 3.3 you get an error that the source is not available:

VS Code gets this source code via the VM Service. When the debugger breaks, we're given an ID of the script for the top frame. If we cannot map this to a local source on disk, we send a getObject request to get the source code. In both versions above, this request is the same (besides isolate IDs, of course):

However, in the response from the VM Service when using Flutter 3.3, the "source" field is missing:

I wasn't able to reproduce this on my Mac, so I suspect this is Windows specific.

Relevant VM Service requests:

• Flutter 3.0 (working)
• Flutter 3.3 (not working)

I'm not certain whether this is a Flutter or Dart issue, but based on a similar issue in the past I think it may be Flutter. If not, please let me know and I can re-raise this in the Dart repo.