Fix forwarding DOTNET_ROOT

src/Cli/dotnet/Commands/Test/TestCommand.cs

@@ -241,11 +241,9 @@ private static TestCommand FromParseResult(ParseResult result, string[] settings
             }
         }
 
-        // Set DOTNET_PATH if it isn't already set in the environment as it is required
-        // by the testhost which uses the apphost feature (Windows only).
-        (bool hasRootVariable, string rootVariableName, string rootValue) = VSTestForwardingApp.GetRootVariable();
-        if (!hasRootVariable)
-        {
+
+        Dictionary<string, string> variables = VSTestForwardingApp.GetVSTestRootVariables();
+        foreach (var (rootVariableName, rootValue) in variables) {
             testCommand.EnvironmentVariable(rootVariableName, rootValue);
             VSTestTrace.SafeWriteTrace(() => $"Root variable set {rootVariableName}:{rootValue}");
         }

src/Cli/dotnet/Commands/Test/VSTestForwardingApp.cs

@@ -14,13 +14,13 @@ public class VSTestForwardingApp : ForwardingApp
     public VSTestForwardingApp(IEnumerable<string> argsToForward)
         : base(GetVSTestExePath(), argsToForward)
     {
-        (bool hasRootVariable, string rootVariableName, string rootValue) = GetRootVariable();
-        if (!hasRootVariable)
+        Dictionary<string, string> variables = GetVSTestRootVariables();
+        foreach (var (rootVariableName, rootValue) in variables)
         {
             WithEnvironmentVariable(rootVariableName, rootValue);
             VSTestTrace.SafeWriteTrace(() => $"Root variable set {rootVariableName}:{rootValue}");
         }
-
+        
         VSTestTrace.SafeWriteTrace(() => $"Forwarding to '{GetVSTestExePath()}' with args \"{argsToForward?.Aggregate((a, b) => $"{a} | {b}")}\"");
     }
 
@@ -38,14 +38,17 @@ private static string GetVSTestExePath()
         return Path.Combine(AppContext.BaseDirectory, VstestAppName);
     }
 
-    internal static (bool hasRootVariable, string rootVariableName, string rootValue) GetRootVariable()
+    internal static Dictionary<string, string> GetVSTestRootVariables()
     {
-        string rootVariableName = Environment.Is64BitProcess ? "DOTNET_ROOT" : "DOTNET_ROOT(x86)";
-        bool hasRootVariable = Environment.GetEnvironmentVariable(rootVariableName) != null;
-        string rootValue = hasRootVariable ? null : Path.GetDirectoryName(new Muxer().MuxerPath);
-
-        // We rename env variable to support --arch switch that relies on DOTNET_ROOT/DOTNET_ROOT(x86)
-        // We provide VSTEST_WINAPPHOST_ only in case of testhost*.exe removing VSTEST_WINAPPHOST_ prefix and passing as env vars.
-        return (hasRootVariable, $"VSTEST_WINAPPHOST_{rootVariableName}", rootValue);
+        // Gather the current .NET SDK dotnet.exe location and forward it to vstest.console.dll so it can use it
+        // to setup DOTNET_ROOT for testhost.exe, to find the same installation of NET SDK that is running `dotnet test`.
+        // This way if we have private installation of .NET SDK, the testhost.exe will be able to use the same private installation.
+        // The way to set the environment is complicated and depends on the version of testhost, so we leave that implementation to vstest console,
+        // we just tell it where the current .net SDK is located, and what is the architecture of it. We don't have more information than that here.
+        return new()
+        {
+            ["VSTEST_DOTNET_ROOT_PATH"] = Path.GetDirectoryName(new Muxer().MuxerPath),
+            ["VSTEST_DOTNET_ROOT_ARCHITECTURE"] = RuntimeInformation.ProcessArchitecture.ToString()
+        };
     }
 }

test/TestAssets/TestProjects/VSTestForwardDotnetRootEnvironmentVariables/Tests.cs

@@ -16,7 +16,7 @@ public void TestForwardDotnetRootEnvironmentVariables()
             // This project is compiled, and executed by the tests in "test/dotnet-test.Tests/GivenDotnetTestForwardDotnetRootEnvironmentVariables.cs"
             foreach (DictionaryEntry env in Environment.GetEnvironmentVariables())
             {
-                if (env.Key.ToString().Contains("VSTEST_WINAPPHOST_"))
+                if (env.Key.ToString().Contains("VSTEST_"))
                 {
                     Console.WriteLine($"{env.Key.ToString()}={env.Value.ToString()}");
                 }

test/dotnet.Tests/CommandTests/Test/GivenDotnetTestForwardDotnetRootEnvironmentVariables.cs

@@ -33,7 +33,8 @@ public void ShouldForwardDotnetRootEnvironmentVariablesIfNotProvided()
                     .Should().Contain("Total tests: 1")
                     .And.Contain("Passed: 1")
                     .And.Contain("Passed TestForwardDotnetRootEnvironmentVariables")
-                    .And.Contain("VSTEST_WINAPPHOST_");
+                    .And.Contain("VSTEST_DOTNET_ROOT_PATH")
+                    .And.Contain("VSTEST_DOTNET_ROOT_ARCHITECTURE");
             }
 
             result.ExitCode.Should().Be(0);