Fix run tests on older versions of the SDK

[dibarbet]

Resolves dotnet/vscode-csharp#6022

There are two parts to this.

b9a4f2b is not the actual bug, however it was preventing me from finding the actual bug. Essentially we were not respecting the user's global.json configured for the workspace because we ran dotnet --info outside of the project. This meant we always used whatever the machine default dotnet value was and the global.json was ignored.

f46a316 Fixes the actual issue - the vstest console included in older SDKs (e.g. .net6) will throw if we pass a null run settings value to the API. The fix is to pass an empty run settings value instead.

Before:

Starting test discovery
Logging TestHost Diagnostics in file: c:\Users\WDAGUtilityAccount\AppData\Roaming\Code\logs\20230803T165938\window1\exthost\ms-dotnettools.csharp\testLogs\vsTestLogs.host.23-08-03_18-01-59_40586_9.txt
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.3+1b45f5407b (64-bit .NET 6.0.20)
[xUnit.net 00:00:00.28]   Discovering: UnitTests
[xUnit.net 00:00:00.31]   Discovered:  UnitTests
Found 1 tests in 851ms

Starting test run
Test run error: System.Exception: Value cannot be null.
   at Microsoft.VisualStudio.TestPlatform.CommandLine.TestPlatformHelpers.TestRequestManager.UpdateRunSettingsIfRequired(String runsettingsXml, IList`1 sources, IBaseTestEventsRegistrar registrar, String& updatedRunSettingsXml, IDictionary`2& sourceToArchitectureMap, IDictionary`2& sourceToFrameworkMap)
   at Microsoft.VisualStudio.TestPlatform.CommandLine.TestPlatformHelpers.TestRequestManager.RunTests(TestRunRequestPayload testRunRequestPayload, ITestHostLauncher3 testHostLauncher, ITestRunEventsRegistrar testRunEventsRegistrar, ProtocolConfig protocolConfig)
   at Microsoft.VisualStudio.TestPlatform.Client.DesignMode.DesignModeClient.<>c__DisplayClass23_0.<StartTestRun>b__0()

After

Starting test discovery
Logging TestHost Diagnostics in file: c:\Users\WDAGUtilityAccount\AppData\Roaming\Code\logs\20230803T165938\window1\exthost\ms-dotnettools.csharp\testLogs\vsTestLogs.host.23-08-03_18-06-35_59571_9.txt
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.3+1b45f5407b (64-bit .NET 6.0.20)
[xUnit.net 00:00:00.20]   Discovering: UnitTests
[xUnit.net 00:00:00.22]   Discovered:  UnitTests
Found 1 tests in 693ms

Starting test run
[Passed] UnitTests.UnitTest1.Test1
==== Summary ====
Passed!  - Failed:    0, Passed:    1, Skipped:    0, Total:    1, Duration: 237ms

[KPGDL]

How to workaround this without waiting for fix?

[dibarbet]

How to workaround this without waiting for fix?

For now, either downgrade the extension or set the flag dotnet.server.useOmnisharp and reload.