Add MSBuild and CMake build integration for WSLC container images

[shuaiyuanxx]

Summary of the Pull Request

Add build-system integration to the Microsoft.WSL.Containers NuGet package so that developers can declaratively build WSLC container images as part of their MSBuild (C++/C#) and CMake workflows, with full incremental rebuild support.

Developers declare <WslcImage> items (MSBuild) or call wslc_add_image() (CMake) in their project, and the build system automatically invokes wslc image build after the main build, skipping the step when sources haven't changed.

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

New files

File	Description
build/Microsoft.WSL.Containers.common.targets	Core MSBuild targets shared by C++ and C#: wslc CLI validation (WSLC0001), item metadata validation (WSLC0002–WSLC0004), incremental image build via stamp files, design-time build guard, and clean target
build/native/Microsoft.WSL.Containers.targets	C++ specific: writes .tlog files for VS Fast Up-to-Date Check
build/net/Microsoft.WSL.Containers.targets	C# specific: registers CPS UpToDateCheckInput/UpToDateCheckBuilt items for VS up-to-date check
cmake/Microsoft.WSL.ContainersConfig.cmake	wslc_add_image() CMake function with target name validation, IMAGE validation, path normalization, CONFIGURE_DEPENDS glob, and CONTEXT fallback when SOURCES is omitted

Usage — MSBuild (C++ / C#)

<ItemGroup>
  <WslcImage Include="echo-server"
             Dockerfile="container\server\Dockerfile"
             Context="container\server"
             Tag="latest"
             Sources="container\server;container\shared" />
</ItemGroup>

Usage — CMake

find_package(Microsoft.WSL.Containers REQUIRED)
wslc_add_image(echo-server
    IMAGE       ghcr.io/myorg/echo-server
    DOCKERFILE  container/Dockerfile
    CONTEXT     container/
    SOURCES     container/src/*.cpp container/src/*.h
    TAG         latest
)
add_dependencies(my_app echo-server)

Key design decisions

• Stamp files for incremental tracking — MSBuild Inputs/Outputs and CMake DEPENDS/OUTPUT use a timestamp stamp file (wslc_<name>.built) to skip rebuilds when no source files have changed.
• No image export — wslc image build is the terminal step; image save/export is not included and can be added later when wslc image save stabilizes.
• Semicolon-safe property passing — Sources metadata is escaped via $([MSBuild]::Escape()) before passing through MSBuild task Properties=, and unescaped at the consumption site, so multi-directory paths work correctly.
• Design-time build guard — All build and validation targets are skipped when $(DesignTimeBuild) == 'true' to avoid slowing down the VS IDE.
• Input validation — Dockerfile and Context are required; Identity is validated against invalid filename characters with actionable error codes (WSLC0001–WSLC0004). CMake IMAGE parameter is validated to not contain : (use TAG separately).

Validation Steps Performed

All tests run locally against wslc 2.8.1 on Windows 11 (26200):

Test	Result
C++ MSBuild: fresh build	Pass
C++ MSBuild: incremental skip (no changes)	Pass
C++ MSBuild: rebuild on source change (multi-directory Sources)	Pass
C++ MSBuild: clean removes stamp	Pass
C# (.NET 8): fresh build	Pass
C# (.NET 8): incremental skip	Pass
C# (.NET 8): rebuild on source change	Pass
CMake (VS 2022 generator): configure	Pass
CMake: fresh build	Pass
CMake: incremental skip	Pass
CMake: rebuild on source change	Pass
Validation: missing Dockerfile → error WSLC0002	Pass
Validation: Identity with / → error WSLC0004	Pass
CMake: invalid target name → FATAL_ERROR	Pass
CMake: IMAGE with : → FATAL_ERROR	Pass
CMake: empty SOURCES defaults to CONTEXT contents	Pass

[benhillis]

Hey @shuaiyuanxx 👋 — Following up on this draft PR. There are 11 unresolved review threads covering design and implementation feedback (flag file vs tar output, image save requirement, target naming, GLOB_RECURSE validation, VS design-time build interference, etc.).

Is this still actively being developed? The PR is marked DO NOT MERGE — just checking in on the status and whether the approach is still the planned direction.

[shuaiyuanxx]

Hey @shuaiyuanxx 👋 — Following up on this draft PR. There are 11 unresolved review threads covering design and implementation feedback (flag file vs tar output, image save requirement, target naming, GLOB_RECURSE validation, VS design-time build interference, etc.).

Is this still actively being developed? The PR is marked DO NOT MERGE — just checking in on the status and whether the approach is still the planned direction.

Hi @benhillis, thanks for following up.

Yes — this is still actively being developed. The design direction has been reviewed and approved via the spec. This PR is ready for review now.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[benhillis]

The feature/wsl-for-apps branch is now defunct. If your PR is still valid, please retarget the master branch. Reach out to @benhillis for help if needed.

The base branch was changed.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.