Build errors when using CommunityToolkit.MVVM with Visual Studio extensions

[stigzler]

Describe the bug

I've asked around on SO and discord, but getting no joy. Forgive me if this is my misunderstanding. My SO post:
I'm getting build errors despite the SourceGenerator apparently working correctly. Example code:

namespace VisGit.ViewModels
{
    public partial class MainViewModel: ObservableObject
    {     
        [ObservableProperty]
        string _exceptionMessageText = "Exception Text";

        public MainViewModel()
        {
            ExceptionMessageText = "Test Change";
        }
    }
}

Intellisense shows the public property ExceptionMessageText as being generated successfully:

Also, source generator appears to work:

However, I get the build error The name 'ExceptionMessageText' does not exist in the current context:

Full code: https://github.com/stigzler/VisGit/blob/1-setup-base-extension-environment/VisGit/ViewModels/MainViewModel.cs

Not sure what I'm dong wrong. I'm using .net Framework 4.8 (is that the issue?). Any ideas?

Regression

No response

Steps to reproduce

1. Create a new VSIX Project w/Tool Window project
2. Create any Class creating a new ObservableProperty via the Attribute

Expected behavior

priavte var is converted to Public property and usable in same class. Project also builds without error "The name '[x]' does not exist in the current context"

Screenshots

See OP

IDE and version

VS 2022

IDE version

4.8.09032

Nuget packages

• CommunityToolkit.Common
• CommunityToolkit.Diagnostics
• CommunityToolkit.HighPerformance
• CommunityToolkit.Mvvm (aka MVVM Toolkit)

Nuget package version(s)

8.2.2

Additional context

No response

Help us help you

Yes, I'd like to be assigned to work on this item

[stigzler]

I've narrowed it down some more. As getting more help on SO, have posted details there:

https://stackoverflow.com/questions/78619310/build-errors-when-using-communitytoolkit-mvvm-with-visual-studio-extensions

It feels like this really doesn't play nicely with VS Extensions. :(