.NET 7 Preview: Reflection, COM interop regressions

[ClearScriptLib]

Greetings!

As a bridge between .NET and external script engines, our project makes heavy use of reflection, COM interop, and the dynamic infrastructure.

Today we started testing on .NET 7 (currently Preview 7), and we're seeing numerous regressions in these areas. After encountering no major issues on .NET Core 3.1, .NET 5, or .NET 6, our code can't get off the ground at all on .NET 7.

Before we start writing up issues, we were wondering if significant breaking changes in these areas are expected in .NET 7.

Thanks!

[stephentoub]

cc: @AaronRobinsonMSFT

[danmoseley]

@dotnet/interop-contrib

[AaronRobinsonMSFT]

we're seeing numerous regressions in these areas

@ClearScriptLib Oh boy. You're scaring me. It would seem your product is using all the of the sensitive bits. The short answer is no, nothing has intentionally changed to warrant substantial regressions. The COM interop sub-system has remained untouched to the best of my knowledge, however Reflection is the sticky bit.IUnknown-based COM interop shouldn't have any changes since .NET 6. However, since you mentioned scripting that means IDispatch is likely in play and that heavily relies upon .NET Reflection, which has been updated in a myriad of ways. We had found a few regressions in Reflection and fixed them, but there are possibly others.

With all that in mind, it would be helpful to understand what "regressions" means. Is this performance or functional regressions? Do you have some simple examples we could look at?

/cc @steveharter

[jkoritzinsky]

I think our build only works with VS2022 nowadays. I think we dropped support for building with VS2019.

[ClearScriptLib]

Folks,

Thanks for all your help so far.

We've managed to build the runtime (didn't need CMake but needed Python 😉) and verified the fix in a simple test:

> dotnet run --fx-version 7.0.0-dev -c Release -f net7.0
-> System.Console.WriteLine('Hello, world!')
Hello, world!
->

However, to run our full suite, we need -f net7.0-windows. The following doesn't work:

> dotnet run --fx-version 7.0.0-dev -c Release -f net7.0-windows
The specified framework 'Microsoft.NETCore.App', version '7.0.0-dev', apply_patches=0, version_compatibility_range=exact cannot roll-forward to the previously referenced version '7.0.0-preview.7.22375.6'.

The error message seems to suggest that we need to build and install the Windows support as well. How does one do that?

Thanks again!

[ClearScriptLib]

Actually, we might be able to run the bulk of the suite without net7.0-windows. In either case, we need to force dotnet test to use the locally-built 7.0.0-dev runtime, but dotnet test doesn't seem to support --fx-version. Suggestions?

[ClearScriptLib]

Update: A hacky solution to be sure, but we've managed to run our full test suite on the patched runtime by renaming directories in C:\Program Files\dotnet\shared\Microsoft.NETCore.App. As far as we can tell, the problem is fixed! Thank you!

[AaronRobinsonMSFT]

Thank you @ClearScriptLib. Your effort is much appreciated.