Test explorer won't discover tests if any project TFM is incompatible with the current platform

Describe the Issue

I was trying to run some Roslyn compiler tests on my Mac and hit the following error:

2026-04-21 15:04:07.332 [error] Test discovery was aborted. See troubleshooting guidance: https://aka.ms/csdk-test-trouble
2026-04-21 15:04:07.339 [info] You must install or update .NET to run this application.
2026-04-21 15:04:07.346 [info] App: /Users/rikkigibson/src/roslyn/artifacts/bin/Microsoft.CodeAnalysis.Workspaces.UnitTests/Debug/net10.0-windows/testhost.dll
2026-04-21 15:04:07.350 [info] Architecture: arm64
2026-04-21 15:04:07.353 [info] Framework: 'Microsoft.WindowsDesktop.App', version '10.0.0' (arm64)
2026-04-21 15:04:07.355 [info] .NET location: /usr/local/share/dotnet/
2026-04-21 15:04:07.356 [info] No frameworks were found.
2026-04-21 15:04:07.358 [info] Learn more:
2026-04-21 15:04:07.364 [info] https://aka.ms/dotnet/app-launch-failed
2026-04-21 15:04:07.366 [info] To install missing framework, download:
2026-04-21 15:04:07.370 [info] https://aka.ms/dotnet-core-applaunch?framework=Microsoft.WindowsDesktop.App&framework_version=10.0.0&arch=arm64&rid=osx-arm64&os=osx.15
2026-04-21 15:04:07.372 [error] System.InvalidOperationException: The provided manager was not found in any slot.
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ParallelOperationManager`3.ClearCompletedSlot(TManager completedManager) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelOperationManager.cs:line 281
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ParallelOperationManager`3.RunNextWork(TManager completedManager) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelOperationManager.cs:line 264
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.Parallel.ParallelProxyDiscoveryManager.HandlePartialDiscoveryComplete(IProxyDiscoveryManager proxyDiscoveryManager, Int64 totalTests, IEnumerable`1 lastChunk, Boolean isAborted) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyDiscoveryManager.cs:line 198
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.Parallel.ParallelDiscoveryEventsHandler.HandleDiscoveryComplete(DiscoveryCompleteEventArgs discoveryCompleteEventArgs, IEnumerable`1 lastChunk) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelDiscoveryEventsHandler.cs:line 81
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyDiscoveryManager.InitializeDiscovery(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEventsHandler2 eventHandler, Boolean skipDefaultAdapters) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/ProxyDiscoveryManager.cs:line 160
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyDiscoveryManager.DiscoverTests(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEventsHandler2 eventHandler) in /_/src/vstest/src/Microsoft.TestPlatform.CrossPlatEngine/Client/ProxyDiscoveryManager.cs:line 174

As far as I can tell the issue is related to the fact that the solution has net10.0-windows projects in it. But the project I want to do discovery in uses net10.0.

Steps To Reproduce

Checkout https://github.com/dotnet/roslyn/commit/3b29bf12eaed16a472b0980e277f2c2a9893951a
Restore
Open in VS Code
Open the Test Explorer sidebar.
The test discovery error should pop up automatically but you can also trigger it by running "Refresh Tests".

Expected Behavior

Test discovery would proceed without errors. Optionally, target frameworks such as net10.0-windows would be filtered out of discovery, when running on non-Windows platform, but, I think even this isn't necessary in principle, dotnet test can run such tests on non-Windows as long as actual Windows-specific features are not used.

Environment Information

csdevkit-logs-2026-04-21T21-54-33.zip