Visual Studio 17.2.6 Breaks CommunityToolkit.Mvvm

[jamiehankins]

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

[RikkiGibson]

If you build your project from the developer command prompt and pass -bl it should produce a binary log which you can use to confirm that:

1. multiple source generators are being passed
2. where those generators originate from.

[jamiehankins]

@RikkiGibson

If you build your project from the developer command prompt and pass -bl it should produce a binary log which you can use to confirm that:

1. multiple source generators are being passed
2. where those generators originate from.

Wow, first I've seen of this tool. There's an insane amount of info, but I can't seem to find that needle in this haystack.

Here's the output from building my tiny test project in case you have a better idea of where in there to look.
msbuild.zip

[RikkiGibson]

It's in the Csc task which contains the build errors, under CommandLineArguments

In this case the paths appear to be:

• C:\Users\jamie.hankins\.nuget\packages\communitytoolkit.mvvm\7.1.2\analyzers\dotnet\cs\CommunityToolkit.Mvvm.SourceGenerators.dll
• C:\Users\jamie.hankins\.nuget\packages\communitytoolkit.mvvm\7.1.2\analyzers\dotnet\cs\CommunityToolkit.Mvvm.SourceGenerators.dll

In other words, the two paths are exactly the same. It's odd that msbuild would do that, It feels like the compiler should be modified to give a diagnostic and/or dedupe the duplicate generators. I'll have to look more closely later to confirm that and determine a root cause.

[k-u-s]

Got similar problem after updating from 6.0.6 to 6.0.7 (sdk 6.0.301 to 6.0.302) but with code ganareted via CsWin32

Minimal repro crated by WPF apllication template from Visual studio 2022 and adding mentioned nuget:
WpfApp.Issue62582.zip

Moving code generation to separate class library fixes issue.

dotnet --info

C:\WpfApp.Issue62582>dotnet --info
.NET SDK (reflecting any global.json):
Version: 6.0.302
Commit: c857713418

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22000
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.302\

global.json file:
Not found

Host:
Version: 6.0.7
Architecture: x64
Commit: 0ec02c8c96

.NET SDKs installed:
3.1.400 [C:\Program Files\dotnet\sdk]
5.0.103 [C:\Program Files\dotnet\sdk]
6.0.201 [C:\Program Files\dotnet\sdk]
6.0.301 [C:\Program Files\dotnet\sdk]
6.0.302 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Download .NET:
https://aka.ms/dotnet-download

Learn about .NET Runtimes and SDKs:
https://aka.ms/dotnet/runtimes-sdk-info

dotnet build

C:\WpfApp.Issue62582>dotnet build Microsoft (R) Build Engine version 17.2.0+41abc5629 for .NET Copyright (C) Microsoft Corporation. All rights reserved.

Determining projects to restore...
Restored C:\WpfApp.Issue62582\WpfApp.Issue62582.csproj (in 221 ms).
C:\WpfApp.Issue62582\Microsoft.Windows.CsWin32\Microsoft.Windows.CsWin32.SourceGenerator\Windows.Win32.WINDOW_STYLE.g.cs(23,15): error CS0101: The namespace 'Windows.Win32.UI.WindowsAndMe
ssaging' already contains a definition for 'WINDOW_STYLE' [C:\WpfApp.Issue62582\WpfApp.Issue62582_uddecyia_wpftmp.csproj]

Build FAILED.

C:\WpfApp.Issue62582\Microsoft.Windows.CsWin32\Microsoft.Windows.CsWin32.SourceGenerator\Windows.Win32.WINDOW_STYLE.g.cs(23,15): error CS0101: The namespace 'Windows.Win32.UI.WindowsAndMe
ssaging' already contains a definition for 'WINDOW_STYLE' [C:\WpfApp.Issue62582\WpfApp.Issue62582_uddecyia_wpftmp.csproj]
0 Warning(s)
1 Error(s)

Time Elapsed 00:00:02.94

[DingpingZhang]

This is a generic problem that affects all source generator projects.
It seems to occur only when referenced by the nuget package, If referenced in the following (manual reference), there will be no problem, so the test cases within the source generator project are normal.

    <ProjectReference Include="..\Xxx.Generator\Xxx.Generator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />

[Tum4ik]

I also have faced the same problem with Refit.

[tan-force]

I uninstalled VS 17.2.6 and installed 17.2.5 that used to work. It doesn't anymore :-( Still the same error.

[glennawatson]

@tan-force seems to be related to dotnet 6.0.7 so you may have to uninstall that version

[tan-force]

Yes! Uninstalled dotnet 6.0.7, and now it works. Thank you.

[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"
    }
}

4. Rebuild solution.