Core support for AbsolutePath/FileInfo/DirectoryInfo and ITaskItem<T> as task parameters by baronfel · Pull Request #13971 · dotnet/msbuild

baronfel · 2026-06-05T19:42:12Z

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

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.

…put parameters.

…etadata

The TASKHOST define is no longer set by any project in the main codebase since the .NET 3.5 taskhost was separated into a frozen project. These guards were always evaluating to true. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The out-of-proc task host gathers all [Output] properties and serializes them via TaskParameter. The PR's new AbsolutePath/FileInfo/DirectoryInfo outputs crashed the node: AbsolutePath (a struct) is never null so it always serialized, and Convert.ChangeType threw InvalidCastException because it is not IConvertible; FileInfo/DirectoryInfo additionally hit Assumed.Unreachable in the constructor. Route FileInfo/DirectoryInfo (scalar and array) to ValueType/ValueTypeArray, and convert values on the write side using ValueTypeParser.ToString - the same canonical conversion the in-process engine uses in TaskExecutionHost.GetValueOutputs - so in-proc and out-of-proc produce identical strings. Harden ValueTypeParser.ToString for a default AbsolutePath (null Value). The legacy net35 task host is intentionally untouched. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Unwrap TargetInvocationException in CreateTaskItemOfT so that parse errors from value-type constructors surface as the original exception (typically InvalidProjectFileException) rather than being wrapped in TargetInvocationException, which was swallowed by the outer catch. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

TaskItemData throws InvalidOperationException on all write operations (SetMetadata, RemoveMetadata, CopyMetadataTo). Switch the TaskItem<T>(T) constructor to use Utilities.TaskItem as the backing item, which supports full metadata mutation as expected by ITaskItem consumers. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

When constructing TaskItem<T> from an ITaskItem where T is FileInfo, DirectoryInfo, or AbsolutePath, prefer the FullPath metadata (which the MSBuild item system computes as an absolute rooted path) over ItemSpec, which may be a relative path. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Replace Value?.Equals(other.Value) with EqualityComparer<T>.Default.Equals to avoid boxing for value types, correctly handle null reference types, and use the appropriate comparer for each type T. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The code already correctly handles ITaskItem<T>[] for both input (IsValidVectorInputParameter) and output (IsAssignableToITaskItem), but had no explicit test coverage. Add tests for all four methods covering scalar and array ITaskItem<T> to prevent future regressions. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Treat arrays with ITaskItem-implementing element types as assignable outputs so TaskItem<T>[] follows the item-output path consistently with TaskExecutionHost behavior. Add unit tests covering TaskItem<int>[] assignability and output validity. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…nfo, DirectoryInfo) in PR1 Value-type T (int, bool, etc.) support for ITaskItem<T> will be added in a subsequent PR. Also remove ITaskItem<int> tests from PR1 test files. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Move TaskExecutionHost's duplicated path-like TaskItem<T>/ITaskItem<T> helper logic into TaskParameterTypeVerifier so type checks and typed item construction are centralized and reusable. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Rename ITaskItem_T.cs to ITaskItem`1.cs; file-scoped namespace - Move ValueTypeParser into Framework - Revert net35 task-host typed-parameter support - Refactor TaskParameterTypeVerifier with s_supportedTypes switch - Remove reflection in TaskParameterValueStringConverter - Consolidate string-to-value conversion via ConvertStringToParameterValue - Flatten GetItemOutputs with early returns - Rename TaskItemTypeHelper to TaskItemTypeDetector - Remove low-value comments; trim docs Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The inlined reflection passed the closed TaskItem<T>/ITaskItem<T> type to MakeGenericType instead of its generic argument, producing TaskItem<TaskItem<FileInfo>> instead of TaskItem<FileInfo>. This broke TaskExecutionHost_Tests for path-like ITaskItem<T>/TaskItem<T> parameters with 'Cannot parse ... as type ITaskItem\1'. Extract GetGenericArguments()[0] before constructing the closed type. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

baronfel · 2026-06-18T02:28:19Z

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.

Adds an opt-in TestEnvironment mechanism to publish files (e.g. binary logs from out-of-process MSBuild invocations) as CI build artifacts. On cleanup, registered files are copied into artifacts/log/<Config>/TestArtifacts (already published by CI), attached to the xUnit result best-effort, and logged. Publication is failure-gated by default via xUnit v3 TestContext, with an 'always' override. Wires the BuildCheck binary-log EndToEndTests to register their binlogs so out-of-process failures are diagnosable in CI. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

baronfel changed the title ~~typed params/core~~ Core support for AbsolutePath/FileInfo/DirectoryInfo and ITaskItem<T> as task parameters Jun 5, 2026

This was referenced Jun 5, 2026

Add Roslyn analyzers (MSBuildTask0006/0007) to suggest typed task parameters #13972

Draft

Expand ITaskItem<T> binding to support arbitrary value types (int, bool, etc.) #13974

Draft

baronfel marked this pull request as ready for review June 5, 2026 19:48

Copilot AI review requested due to automatic review settings June 5, 2026 19:48

Copilot started reviewing on behalf of baronfel June 5, 2026 19:49 View session

Copilot AI reviewed Jun 5, 2026

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baronfel assigned jankratochvilcz Jun 5, 2026

baronfel commented Jun 6, 2026

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Comment thread src/Shared/UnitTests/TaskParameter_Tests.cs

Comment thread src/Build.UnitTests/BackEnd/TaskParameterTypeVerifier_Tests.cs

Comment thread src/Build.UnitTests/BackEnd/TaskExecutionHost_Tests.cs

baronfel requested a review from a team June 8, 2026 15:00

jankratochvilcz requested changes Jun 9, 2026

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teo-tsirpanis reviewed Jun 9, 2026

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Comment thread documentation/wiki/Tasks.md Outdated

rainersigwald reviewed Jun 12, 2026

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baronfel and others added 17 commits June 17, 2026 13:53

support binding to AbsolutePath and AbsolutePath[] for task input/out…

e2dee51

…put parameters.

Allow users to bind to primitive types while still having access to m…

1288b46

…etadata

Support FileInfo/DirectoryInfo parameter binding as well

9bb2eac

Potential fix for pull request finding

af443dd

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Use existing boolean conversion helpers instead of reimplementing

e79b236

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Update docs to align with parsed value types

961fca6

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

actually escape set value in wrapped ITaskItem

f70db5f

baronfel and others added 4 commits June 17, 2026 13:53

fix potential nullrefs on uninitialized TaskItem<T> structs.

7279f54

Unify task parameter helper logic across hosts

4f065f6

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Fix shared task-parameter helpers for TaskHost builds

a8ecf09

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

baronfel force-pushed the typed-params/core branch from a4d536e to b62b5ae Compare June 17, 2026 18:53

Rip out abstracted reflection usage in TaskItem<T> creation

418b3ae

baronfel requested a review from jankratochvilcz June 17, 2026 19:17

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baronfel commented Jun 18, 2026

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baronfel commented Jun 5, 2026 •

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