Add test coverage for NetCoreSdkRoot fallback logic in TaskHostFactory

src/Build.UnitTests/NetTaskHost_E2E_Tests.cs

@@ -163,5 +163,89 @@ public void NetTaskWithImplicitHostParamsTest()
             // Output from the task where neither TaskHost nor Runtime were specified
             testTaskOutput.ShouldContain("Found item: Banana");
         }
+
+        [WindowsFullFrameworkOnlyFact]
+        public void NetTaskHost_WithNetCoreSdkRootSet_UsesNetCoreSdkRootDirectly()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            var dotnetPath = env.GetEnvironmentVariable("DOTNET_ROOT");
+
+            string testProjectPath = Path.Combine(TestAssetsRootPath, "ExampleNetTask", "TestNetCoreSdkRootDirect", "TestNetCoreSdkRootDirect.csproj");
+
+            string testTaskOutput = RunnerUtilities.ExecBootstrapedMSBuild($"{testProjectPath} -restore -v:n", out bool successTestTask);
+
+            if (!successTestTask)
+            {
+                _output.WriteLine(testTaskOutput);
+            }
+
+            successTestTask.ShouldBeTrue();
+            // Verify the task ran successfully with NetCoreSdkRoot property set
+            testTaskOutput.ShouldContain($"The task is executed in process: dotnet");
+            testTaskOutput.ShouldContain($"Process path: {dotnetPath}", customMessage: testTaskOutput);
+            testTaskOutput.ShouldContain("NetCoreSdkRoot test:");
+        }
+
+        [WindowsFullFrameworkOnlyFact]
+        public void NetTaskHost_WithRuntimeIdentifierGraphPath_FallsBackToRIDGraph()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+            var dotnetPath = env.GetEnvironmentVariable("DOTNET_ROOT");
+
+            string testProjectPath = Path.Combine(TestAssetsRootPath, "ExampleNetTask", "TestRIDGraphFallback", "TestRIDGraphFallback.csproj");
+
+            string testTaskOutput = RunnerUtilities.ExecBootstrapedMSBuild($"{testProjectPath} -restore -v:n", out bool successTestTask);
+
+            if (!successTestTask)
+            {
+                _output.WriteLine(testTaskOutput);
+            }
+
+            successTestTask.ShouldBeTrue();
+            // Verify the task ran successfully with fallback to RuntimeIdentifierGraphPath
+            testTaskOutput.ShouldContain($"The task is executed in process: dotnet");
+            testTaskOutput.ShouldContain($"Process path: {dotnetPath}", customMessage: testTaskOutput);
+            testTaskOutput.ShouldContain("RIDGraphFallback test");
+        }
+
+        [WindowsFullFrameworkOnlyFact]
+        public void NetTaskHost_WithNoSDKProperties_StillSucceeds()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+
+            string testProjectPath = Path.Combine(TestAssetsRootPath, "ExampleNetTask", "TestNoSDKProperties", "TestNoSDKProperties.csproj");
+
+            string testTaskOutput = RunnerUtilities.ExecBootstrapedMSBuild($"{testProjectPath} -restore -v:n", out bool successTestTask);
+
+            if (!successTestTask)
+            {
+                _output.WriteLine(testTaskOutput);
+            }
+
+            // The task should still succeed even without SDK properties
+            // This tests the scenario where the fallback returns original parameters
+            successTestTask.ShouldBeTrue();
+            testTaskOutput.ShouldContain("NoSDKProperties test completed");
+        }
+
+        [WindowsFullFrameworkOnlyFact]
+        public void NetTaskHost_WithRIDGraphPathAtRoot_HandlesEdgeCase()
+        {
+            using TestEnvironment env = TestEnvironment.Create(_output);
+
+            string testProjectPath = Path.Combine(TestAssetsRootPath, "ExampleNetTask", "TestRIDGraphEdgeCase", "TestRIDGraphEdgeCase.csproj");
+
+            string testTaskOutput = RunnerUtilities.ExecBootstrapedMSBuild($"{testProjectPath} -restore -v:n", out bool successTestTask);
+
+            if (!successTestTask)
+            {
+                _output.WriteLine(testTaskOutput);
+            }
+
+            // The task should succeed even with edge case RID graph path
+            // This tests that Path.GetDirectoryName returning null or empty is handled correctly
+            successTestTask.ShouldBeTrue();
+            testTaskOutput.ShouldContain("RIDGraphEdgeCase test");
+        }
     }
 }

src/Build.UnitTests/TestAssets/ExampleNetTask/TestNetCoreSdkRootDirect/TestNetCoreSdkRootDirect.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <!-- Explicitly set NetCoreSdkRoot to verify it's used directly -->
+    <NetCoreSdkRoot>$(MSBuildSDKsPath)\..</NetCoreSdkRoot>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TestProjectFolder>$([System.IO.Path]::GetFullPath('$([System.IO.Path]::Combine('$(AssemblyLocation)', '..'))'))</TestProjectFolder>
+    <ExampleTaskPath>$([System.IO.Path]::Combine('$(TestProjectFolder)', '$(TargetFramework)', 'ExampleTask.dll'))</ExampleTaskPath>
+  </PropertyGroup>
+
+  <UsingTask
+	    TaskName="ExampleTask"
+      AssemblyFile="$(ExampleTaskPath)"
+      TaskFactory="TaskHostFactory"
+	    Runtime="NET"/>
+
+  <Target Name="TestTask" BeforeTargets="Build">
+	  <ExampleTask />
+    <Message Text="NetCoreSdkRoot test: $(NetCoreSdkRoot)" Importance="high" />
+  </Target>
+
+</Project>

src/Build.UnitTests/TestAssets/ExampleNetTask/TestNetCoreSdkRootDirect/global.json

@@ -0,0 +1,9 @@
+{
+    "sdk": {
+        // This global.json is needed to prevent builds running in tests using the bootstrap layout from walking
+        // up the repo tree and resolving our sdk.paths, instead of the bootstrap layout's SDK.
+        // See https://github.com/dotnet/runtime/issues/118488 for details.
+        "allowPrerelease": true,
+        "rollForward": "latestMajor"
+    }
+}

src/Build.UnitTests/TestAssets/ExampleNetTask/TestNoSDKProperties/TestNoSDKProperties.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <!-- Explicitly clear both properties to test behavior when both are missing -->
+    <NetCoreSdkRoot></NetCoreSdkRoot>
+    <RuntimeIdentifierGraphPath></RuntimeIdentifierGraphPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TestProjectFolder>$([System.IO.Path]::GetFullPath('$([System.IO.Path]::Combine('$(AssemblyLocation)', '..'))'))</TestProjectFolder>
+    <ExampleTaskPath>$([System.IO.Path]::Combine('$(TestProjectFolder)', '$(TargetFramework)', 'ExampleTask.dll'))</ExampleTaskPath>
+  </PropertyGroup>
+
+  <UsingTask
+	    TaskName="ExampleTask"
+      AssemblyFile="$(ExampleTaskPath)"
+      TaskFactory="TaskHostFactory"
+	    Runtime="NET"/>
+
+  <Target Name="TestTask" BeforeTargets="Build">
+	  <ExampleTask />
+    <Message Text="NoSDKProperties test completed" Importance="high" />
+  </Target>
+
+</Project>

src/Build.UnitTests/TestAssets/ExampleNetTask/TestNoSDKProperties/global.json

@@ -0,0 +1,9 @@
+{
+    "sdk": {
+        // This global.json is needed to prevent builds running in tests using the bootstrap layout from walking
+        // up the repo tree and resolving our sdk.paths, instead of the bootstrap layout's SDK.
+        // See https://github.com/dotnet/runtime/issues/118488 for details.
+        "allowPrerelease": true,
+        "rollForward": "latestMajor"
+    }
+}

src/Build.UnitTests/TestAssets/ExampleNetTask/TestRIDGraphEdgeCase/TestRIDGraphEdgeCase.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <!-- Explicitly clear NetCoreSdkRoot to test fallback -->
+    <NetCoreSdkRoot></NetCoreSdkRoot>
+    <!-- Set RuntimeIdentifierGraphPath to a file in a near-root directory to test edge case -->
+    <RuntimeIdentifierGraphPath Condition="$([MSBuild]::IsOSPlatform('Windows'))">\runtime.json</RuntimeIdentifierGraphPath>
+    <RuntimeIdentifierGraphPath Condition="!$([MSBuild]::IsOSPlatform('Windows'))">/runtime.json</RuntimeIdentifierGraphPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TestProjectFolder>$([System.IO.Path]::GetFullPath('$([System.IO.Path]::Combine('$(AssemblyLocation)', '..'))'))</TestProjectFolder>
+    <ExampleTaskPath>$([System.IO.Path]::Combine('$(TestProjectFolder)', '$(TargetFramework)', 'ExampleTask.dll'))</ExampleTaskPath>
+  </PropertyGroup>
+
+  <UsingTask
+	    TaskName="ExampleTask"
+      AssemblyFile="$(ExampleTaskPath)"
+      TaskFactory="TaskHostFactory"
+	    Runtime="NET"/>
+
+  <Target Name="TestTask" BeforeTargets="Build">
+	  <ExampleTask />
+    <Message Text="RIDGraphEdgeCase test - RIDGraphPath: $(RuntimeIdentifierGraphPath)" Importance="high" />
+  </Target>
+
+</Project>

src/Build.UnitTests/TestAssets/ExampleNetTask/TestRIDGraphEdgeCase/global.json

@@ -0,0 +1,9 @@
+{
+    "sdk": {
+        // This global.json is needed to prevent builds running in tests using the bootstrap layout from walking
+        // up the repo tree and resolving our sdk.paths, instead of the bootstrap layout's SDK.
+        // See https://github.com/dotnet/runtime/issues/118488 for details.
+        "allowPrerelease": true,
+        "rollForward": "latestMajor"
+    }
+}

src/Build.UnitTests/TestAssets/ExampleNetTask/TestRIDGraphFallback/TestRIDGraphFallback.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <!-- Explicitly clear NetCoreSdkRoot to test fallback to RuntimeIdentifierGraphPath -->
+    <NetCoreSdkRoot></NetCoreSdkRoot>
+    <!-- Set RuntimeIdentifierGraphPath to simulate .NET 10 and earlier behavior -->
+    <RuntimeIdentifierGraphPath>$(MSBuildSDKsPath)\..\runtime.json</RuntimeIdentifierGraphPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <TestProjectFolder>$([System.IO.Path]::GetFullPath('$([System.IO.Path]::Combine('$(AssemblyLocation)', '..'))'))</TestProjectFolder>
+    <ExampleTaskPath>$([System.IO.Path]::Combine('$(TestProjectFolder)', '$(TargetFramework)', 'ExampleTask.dll'))</ExampleTaskPath>
+  </PropertyGroup>
+
+  <UsingTask
+	    TaskName="ExampleTask"
+      AssemblyFile="$(ExampleTaskPath)"
+      TaskFactory="TaskHostFactory"
+	    Runtime="NET"/>
+
+  <Target Name="TestTask" BeforeTargets="Build">
+	  <ExampleTask />
+    <Message Text="RIDGraphFallback test - RIDGraphPath: $(RuntimeIdentifierGraphPath)" Importance="high" />
+  </Target>
+
+</Project>

src/Build.UnitTests/TestAssets/ExampleNetTask/TestRIDGraphFallback/global.json

@@ -0,0 +1,9 @@
+{
+    "sdk": {
+        // This global.json is needed to prevent builds running in tests using the bootstrap layout from walking
+        // up the repo tree and resolving our sdk.paths, instead of the bootstrap layout's SDK.
+        // See https://github.com/dotnet/runtime/issues/118488 for details.
+        "allowPrerelease": true,
+        "rollForward": "latestMajor"
+    }
+}