Visual Studio 17.2.6 Breaks CommunityToolkit.Mvvm

Version Used: 17.2.6

Steps to Reproduce:

1. Create a WPF exe project targeting net6.0-windows
2. Reference CommunityToolkit.Mvvm like so: <PackageReference Include="CommunityToolkit.Mvvm" Version="7.1.2" />
3. Create a simple class inheriting from ObservableObject, like so:

using CommunityToolkit.Mvvm.ComponentModel;

namespace ObservablePropertyTest
{
    public partial class TestVM : ObservableObject
    {
        [ObservableProperty]
        private string _testString = string.Empty;
    }
}

Expected Behavior: In 17.2.5, it built and ran fine.

Actual Behavior:

Rebuild started...
1>------ Rebuild All started: Project: ObservablePropertyTest, Configuration: Debug Any CPU ------
Restored C:\git\ObservablePropertyTest\ObservablePropertyTest.csproj (in 2 ms).
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(12,27,12,70): error CS0101: The namespace 'CommunityToolkit.Mvvm.ComponentModel.__Internals' already contains a definition for '__KnownINotifyPropertyChangedOrChangingArgs'
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(7,6,7,51): error CS0579: Duplicate 'global::System.CodeDom.Compiler.GeneratedCode' attribute
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(8,6,8,52): error CS0579: Duplicate 'global::System.Diagnostics.DebuggerNonUserCode' attribute
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(9,6,9,69): error CS0579: Duplicate 'global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage' attribute
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(10,6,10,51): error CS0579: Duplicate 'global::System.ComponentModel.EditorBrowsable' attribute
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\__KnownINotifyPropertyChangedOrChangingArgs.cs(11,6,11,29): error CS0579: Duplicate 'global::System.Obsolete' attribute
1>C:\git\ObservablePropertyTest\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator\ObservablePropertyTest.TestVM.cs(12,23,12,33): error CS0102: The type 'TestVM' already contains a definition for 'TestString'
1>Done building project "ObservablePropertyTest_yynlzhol_wpftmp.csproj" -- FAILED.
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

It appears that somehow the CommunityToolkit.Mvvm source generators are being run twice.

If you create a WPF class library, things work fine. They’re only broken in a WPF app.

Here is my test project: ObservablePropertyTest.zip

[rainersigwald]

For a workaround @ThomasGoulet73 I tend to prefer @jlaanstra’s from https://github.com/dotnet/wpf/pull/6680#issuecomment-1183552170 with a small modification to use MSBuild engine functionality instead of a task:

<Target Name="RemoveDuplicateAnalyzers" BeforeTargets="CoreCompile">
    <!-- Work around https://github.com/dotnet/wpf/issues/6792 -->

    <ItemGroup>
        <FilteredAnalyzer Include="@(Analyzer->Distinct())" />
        <Analyzer Remove="@(Analyzer)" />
        <Analyzer Include="@(FilteredAnalyzer)" />
    </ItemGroup>
</Target>

[Tum4ik]

You still can use the latest version of Visual Studio. Here is a workaround that works for me:

1. Download and install the previous version of .NET SDK (6.0.301) https://dotnet.microsoft.com/en-us/download/dotnet/6.0
2. Add global.json file to the root of your solution (where .sln file is located)
3. The content of the global.json:

{
    "sdk": {
        "version": "6.0.301",
        "rollForward": "disable"
    }
}

1. Rebuild solution.