NU1511 warnings/errors for test projects with .NET 10 SDK

[tmds]

Some of our CI jobs that use a daily SDK build are failing. The SDK emits warnings for unused packages, and these warnings are then turned into errors.

See dotnet/core#9752 for info about the pruning warnings.

For example:

/home/tester/runtime/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/System.Text.RegularExpressions.Tests.csproj : error NU1510: Warning As Error: PackageReference Microsoft.VisualBasic will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/System.Text.RegularExpressions.Tests.csproj : error NU1510: Warning As Error: PackageReference System.Formats.Asn1 will not be pruned. Consider removing this package from your dependencies, as it is likely unnecessary. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/System.Text.Json.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Text.Json. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/System.Text.Json.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.IO.Pipelines. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/System.Text.Json.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Linq.AsyncEnumerable. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn4.4.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.IO.Pipelines. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn4.4.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Reflection.Metadata. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn4.4.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Text.Json. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn3.11.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.IO.Pipelines. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn3.11.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Reflection.Metadata. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/System.Text.Json.SourceGeneration.Roslyn3.11.Unit.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Text.Json. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Roslyn4.4.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Text.Json. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Roslyn3.11.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Text.Json. [/home/tester/runtime/Build.proj]
/home/tester/runtime/src/libraries/System.Runtime/tests/System.Text.Encoding.Tests/System.Text.Encoding.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.IO.Pipelines. [/home/tester/runtime/Build.proj]
...

cc @ViktorHofer @nkolev92 @omajid

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[ViktorHofer]

Thanks for the ping. This will now also show up in #112730 and we will handle it there.

[tmds]

@ViktorHofer this issue was fixed, but I'm seeing a new instance:

src/libraries/System.Net.ServerSentEvents/tests/System.Net.ServerSentEvents.Tests.csproj : error NU1511: Warning As Error: A ProjectReference cannot be pruned, System.Net.ServerSentEvents.

This is when building the runtime repo with a 10.0.100-preview.5.25258.26 SDK. It may be due to the newer SDK.

Additionally, even though my build invocation has --warnAsError false, this causes the build to fail with an error.

[ViktorHofer]

Interesting. That library got moved inbox with 478cfe2 and dotnet/runtime uses an SDK that includes that commit. But we only then only later added the library to PackageOverrides.txt which is the input to NuGet package pruning: 819bff1

We have a tracking issue to auto-generate the PackageOverrides.txt file so that it keeps in sync with its inputs: #113984

So this needs to be fixed for runtime and would show up for us as well in the next SDK upgrade. It doesn't show up in source-build's stage2 build because we don't build tests there. A blind spot.

I submitted #115470 to fix this in runtime.