diff --git a/src/Shared/TaskFactoryUtilities.cs b/src/Shared/TaskFactoryUtilities.cs
index 1dc8353799e..b773a23393b 100644
--- a/src/Shared/TaskFactoryUtilities.cs
+++ b/src/Shared/TaskFactoryUtilities.cs
@@ -267,5 +267,28 @@ public static bool ShouldCompileForOutOfProcess(IBuildEngine taskFactoryEngineCo
return null;
}
+
+ ///
+ /// Resolves a potentially relative source code file path for inline task factories.
+ /// In multithreaded mode (/mt), relative paths are resolved relative to the project file directory
+ /// rather than the current working directory. In other modes, the path is returned unchanged.
+ ///
+ /// The source code file path to resolve (may be relative or absolute).
+ /// Whether the build is running in multithreaded mode.
+ /// The directory of the project file.
+ /// The resolved absolute path in multithreaded mode, or the original path otherwise.
+ ///
+ /// This method only modifies path resolution in multithreaded builds to maintain
+ /// backward compatibility with existing multi-process build behavior.
+ ///
+ public static string ResolveTaskSourceCodePath(string path, bool isMultiThreadedBuild, string projectDirectory)
+ {
+ if (!isMultiThreadedBuild || Path.IsPathRooted(path))
+ {
+ return path;
+ }
+
+ return Path.Combine(projectDirectory, path);
+ }
}
}
diff --git a/src/Tasks.UnitTests/RoslynCodeTaskFactory_Tests.cs b/src/Tasks.UnitTests/RoslynCodeTaskFactory_Tests.cs
index 814ea1e440a..0253b720504 100644
--- a/src/Tasks.UnitTests/RoslynCodeTaskFactory_Tests.cs
+++ b/src/Tasks.UnitTests/RoslynCodeTaskFactory_Tests.cs
@@ -10,10 +10,9 @@
using Microsoft.Build.UnitTests;
using Microsoft.Build.UnitTests.Shared;
using Microsoft.Build.Utilities;
-#if NETFRAMEWORK
-using Microsoft.IO;
-#else
using System.IO;
+#if NETFRAMEWORK
+using MicrosoftIO = Microsoft.IO;
#endif
using Shouldly;
using VerifyTests;
@@ -924,7 +923,7 @@ private void TryLoadTaskBodyAndExpectFailure(string taskBody, string expectedErr
TaskResources = Shared.AssemblyResources.PrimaryResources
};
- bool success = RoslynCodeTaskFactory.TryLoadTaskBody(log, TaskName, taskBody, new List(), out RoslynCodeTaskFactoryTaskInfo _);
+ bool success = RoslynCodeTaskFactory.TryLoadTaskBody(log, TaskName, taskBody, new List(), buildEngine, out RoslynCodeTaskFactoryTaskInfo _);
success.ShouldBeFalse();
@@ -950,7 +949,7 @@ private void TryLoadTaskBodyAndExpectSuccess(
TaskResources = Shared.AssemblyResources.PrimaryResources
};
- bool success = RoslynCodeTaskFactory.TryLoadTaskBody(log, TaskName, taskBody, parameters ?? new List(), out RoslynCodeTaskFactoryTaskInfo taskInfo);
+ bool success = RoslynCodeTaskFactory.TryLoadTaskBody(log, TaskName, taskBody, parameters ?? new List(), buildEngine, out RoslynCodeTaskFactoryTaskInfo taskInfo);
buildEngine.Errors.ShouldBe(0, buildEngine.Log);
@@ -1160,5 +1159,365 @@ public void MultiThreadedBuildExecutesInlineTasksSuccessfully()
customMessage: "Inline task should be launched in external task host");
}
}
+
+ ///
+ /// Test that verifies Code Source attribute with relative path resolves correctly relative to the project file, not CWD.
+ /// This test exposes the bug where inline tasks with external code files fail in multi-threaded mode
+ /// because the file path is resolved relative to the multi-threaded process's CWD instead of the project file directory.
+ /// Creates a realistic scenario with nested directories similar to a multi-project solution structure.
+ ///
+ [Theory]
+ [InlineData(false)]
+ [InlineData(true)]
+ public void SourceCodeFromRelativeFilePath_ResolvesRelativeToProjectFile(bool forceOutOfProc)
+ {
+ using (TestEnvironment env = TestEnvironment.Create())
+ {
+ if (forceOutOfProc)
+ {
+ env.SetEnvironmentVariable("MSBUILDFORCEINLINETASKFACTORIESOUTOFPROC", "1");
+ }
+
+ // Create multi-project solution structure
+ // Root/
+ // ├─ solution.sln
+ // ├─ Project1/Project1.csproj (simple project)
+ // └─ Project2/
+ // ├─ Project2.csproj (has inline task with external code)
+ // └─ TaskCode.cs
+ TransientTestFolder rootFolder = env.CreateFolder(createFolder: true);
+ TransientTestFolder project1Folder = env.CreateFolder(Path.Combine(rootFolder.Path, "Project1"), createFolder: true);
+ TransientTestFolder project2Folder = env.CreateFolder(Path.Combine(rootFolder.Path, "Project2"), createFolder: true);
+
+ // Create simple first project
+ env.CreateFile(project1Folder, "Project1.csproj", @"
+
+
+
+
+");
+
+ // Create external code file in Project2 directory
+ const string taskCodeFile = "TaskCode.cs";
+ const string taskCode = @"
+namespace InlineTask
+{
+ using Microsoft.Build.Framework;
+ using Microsoft.Build.Utilities;
+
+ public class CustomTask : Task
+ {
+ public override bool Execute()
+ {
+ Log.LogMessage(MessageImportance.High, ""External task code executed successfully"");
+ return true;
+ }
+ }
+}";
+ env.CreateFile(project2Folder, taskCodeFile, taskCode);
+
+ // Create Project2 with inline task using RELATIVE path to external code
+ env.CreateFile(project2Folder, "Project2.csproj", $@"
+
+
+
+