Bumping version of MessagePack breaks source generation inside VisualStudio

[pziezio]

Actual behavior

f25bc2d updated MessagePack version from 2.2.x to 2.3.x which has some breaking changes regarding serialization of Dictionary<>.

Simple example fails to generate sources inside VisualStudio:
CSC : warning CS8785: Generator 'SourceGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'MessagePackSerializationException' with message 'Failed to deserialize System.Collections.Generic.Dictionary2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[Microsoft.Windows.SDK.Win32Docs.ApiDetails, Microsoft.Windows.SDK.Win32Docs, Version=0.1.4.39555, Culture=neutral, PublicKeyToken=7c40c7c34b1fcfe1]] value.

Compiling project from command line with dotnet build works without problem - that's probably why all automatic tests also works.
I've recompiled CsWin32 with MessagePack version downgraded to 2.2.x and it works again.

Repro steps

1. NativeMethods.txt content:

CreateFile

2. Empty console project with using Windows.Win32;

Context

• CsWin32 version: 0.1.539-beta
• Target Framework: net5.0
• VisualStudio: 2019 and 2022

[pziezio]

When I tried to debug some tests the inner exception says "Could not load file or assembly 'MessagePack.Annotations, Version=2.3.0.0, Culture=neutral, PublicKeyToken=b4a0369545f0a1be' or one of its dependencies. The system cannot find the file specified.".

But that happens only in net472 tests.
\bin\Microsoft.Windows.CsWin32.Tests\Debug\net472 folder does not contain MessagePack.Annotations.dll file.

Since I create a new net5.0 project I don't understand how that relates. Newly created project correctly references CsWin32 with MessagePack and MessagePack.Annotations as it's dependencies.

[AArnott]

Since I create a new net5.0 project I don't understand how that relates.

The target framework of the tests have nothing to do with the target framework of the project being generated into. The test TFM determines the runtime that the source generator itself runs under. net472 evidently doesn't like something the source generator is doing.

Your own project would presumably fail if built with msbuild.exe (or in VS) which uses .NET Framework as well. But your project would probably succeed if built with dotnet build at the command line, since that's using the Core CLR.

[AArnott]

The two issues reported (test failure, failure in real project) were actually two different failures. The test failure was not due to the upgrade. But as the real project failure is due to the upgrade, I have to roll back the upgrade.

The issue is the win32metadata repo ships an assembly that depends on MessagePack.Annotations 2.2.0.0. If we ship 2.3.0.0 of that assembly, then the .NET Framework-based C# compiler does not see these as equal and throws an exception. Roslyn does not provide analyzers a way to supply binding redirects, so we simply have to exactly match the version in win32metadata.