[baronfel]

Summary

Adds support for using AbsolutePath, System.IO.FileInfo, System.IO.DirectoryInfo, and ITaskItem (for path-like T) as MSBuild task input/output parameters, in addition to the existing string and ITaskItem types.

Changes

• AbsolutePath: A new value type that wraps an absolute path string, validated via TaskEnvironment.GetAbsolutePath
• FileInfo / DirectoryInfo: Paths are validated as absolute before creating the FileInfo/DirectoryInfo instance
• ITaskItem<T>: A new generic interface allowing typed access to item specs, with T restricted to AbsolutePath, FileInfo, or DirectoryInfo in this PR
• TaskItem<T>: Implementation of ITaskItem with mutable metadata backing
• ValueTypeParser: Shared utility for parsing/formatting typed values (infrastructure for future PRs)
• Task host serialization support for typed outputs
• Full test coverage for all new parameter types

Performance

A BenchmarkDotNet benchmark (TaskParameterBindingBenchmark) was added that drives the real TaskExecutionHost.SetTaskParameters path to measure the engine's per-parameter binding overhead for the new types against the string and ITaskItem baselines.

Steady-state full-run results (AMD Ryzen 7 5700X3D, BDN v0.13.12), with the ITaskItem<T> constructor-delegate caching applied. Mean is per single parameter bind; Allocated is managed bytes per bind; ratios are vs the string baseline.

net10.0 (.NET 10.0.8)

Parameter type	Mean	Ratio	Allocated	Alloc ratio
string (baseline)	1.68 µs	1.00x	1.05 KB	1.00x
ITaskItem	1.83 µs	1.09x	1.27 KB	1.20x
AbsolutePath	1.91 µs	1.13x	1.88 KB	1.78x
FileInfo	2.31 µs	1.38x	2.28 KB	2.16x
DirectoryInfo	3.08 µs	1.88x	2.27 KB	2.16x
ITaskItem<AbsolutePath>	6.21 µs	2.67x	2.90 KB	2.75x
ITaskItem<FileInfo>	7.16 µs	4.26x	2.91 KB	2.76x
ITaskItem<DirectoryInfo>	7.36 µs	4.06x	2.91 KB	2.76x

net472 (.NET Framework 4.7.2)

Parameter type	Mean	Ratio	Allocated	Alloc ratio
string (baseline)	5.94 µs	1.00x	397 B	1.00x
ITaskItem	7.12 µs	1.24x	593 B	1.49x
AbsolutePath	6.15 µs	1.05x	1346 B	3.39x
FileInfo	7.61 µs	1.26x	1526 B	3.84x
DirectoryInfo	7.38 µs	1.23x	1487 B	3.75x
ITaskItem<AbsolutePath>	12.33 µs	2.06x	1222 B	3.08x
ITaskItem<FileInfo>	15.42 µs	2.67x	1403 B	3.53x
ITaskItem<DirectoryInfo>	14.33 µs	2.39x	1363 B	3.43x

Takeaways:

• Scalar value/path conversions (AbsolutePath, FileInfo, DirectoryInfo) add only ~10–90% over a plain string bind — roughly a microsecond per parameter and ~0.8–1.2 KB / ~0.9–1.1 KB extra allocation, negligible against real task execution.
• The ITaskItem<T> path was the expensive case because the engine wrapped each item via typeof(TaskItem<>).MakeGenericType(...).GetConstructor(...).Invoke(...) on every bind. This PR now caches a compiled Func<ITaskItem, ITaskItem> constructor delegate per generic argument T, so the reflection work happens once. On .NET Framework this cut ITaskItem<T> bind time by ~37–42% (e.g. ~24 µs → ~14–15 µs) and trimmed ~180 B/bind; on .NET 10 the JIT already optimized the reflection well, so the win there is primarily reduced allocations and Gen0 churn (≈3.1 KB → ≈2.9 KB).

Stacked on

• Base: main
• Next: Add Roslyn analyzers (MSBuildTask0006/0007) to suggest typed task parameters #13972 (migration analyzers)

/cc @baronfel

[Copilot]

Pull request overview

Adds core infrastructure to support strongly-typed MSBuild task parameters and outputs for path-like values, including a new AbsolutePath-based flow, FileInfo/DirectoryInfo binding, and generic task items (ITaskItem<T> / TaskItem<T>). This primarily touches the task parameter binding pipeline (TaskExecutionHost), parameter type validation/serialization (TaskParameter*), and adds corresponding unit tests + docs updates.

Changes:

• Introduces ITaskItem<T> (Framework) and TaskItem<T> (Utilities) to enable typed item identities.
• Adds ValueTypeParser and switches task output serialization to a canonical string conversion path.
• Extends TaskExecutionHost binding + unit tests to cover AbsolutePath, FileInfo/DirectoryInfo, and typed task items.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/Utilities/TaskItem_T.cs	New TaskItem<T> struct implementing typed task items over an ITaskItem backing instance.
src/Utilities.UnitTests/TaskItem_Tests.cs	Unit tests for TaskItem<T> metadata behavior and parsing behavior.
src/Tasks/Microsoft.Build.Tasks.csproj	Minor ItemGroup structure tweak.
src/Shared/ValueTypeParser.cs	New shared parser/formatter for value-like task parameter conversions.
src/Shared/UnitTests/TaskParameter_Tests.cs	Adds serialization tests for AbsolutePath / FileInfo / DirectoryInfo.
src/Shared/TaskParameterTypeVerifier.cs	Extends supported parameter types to include typed items and path-related types.
src/Shared/TaskParameter.cs	Updates value-type output serialization to use ValueTypeParser and support FileInfo/DirectoryInfo.
src/Framework/Microsoft.Build.Framework.csproj	Links ValueTypeParser.cs into Framework build.
src/Framework/ITaskItem_T.cs	New public ITaskItem<T> interface.
src/Build/Microsoft.Build.csproj	Adds Build → Utilities project reference (to use TaskItem<T>).
src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs	Adds parameter binding + output gathering support for typed path parameters and typed task items.
src/Build.UnitTests/BackEnd/TaskParameterTypeVerifier_Tests.cs	New tests covering typed parameter validation scenarios.
src/Build.UnitTests/BackEnd/TaskExecutionHost_Tests.cs	Expanded tests for new parameter types and typed task items.
src/Build.UnitTests/BackEnd/TaskBuilderTestTask.cs	Adds test task properties/outputs for new supported parameter types.
documentation/wiki/Tasks.md	Updates docs for supported task parameter types.

[jankratochvilcz]

Left a few comments. The biggest thing we should discuss is whether this is the only architecture viable in the codebase - It would be great to ideate if we can have a more self-contained implementation.

[baronfel]

Remaining test failures are buildcheck related - I can't repro locally, but I also haven't been able to collect binlogs from these tests in the CI pipelines.