[SwiftBuild] Classify `swiftpm-test-runner` as a tool product in SwiftBuild

[kateinoigakukun]

Description

Follow-up from #773.

The SwiftPM synthetic test runner is an executable, but SwiftBuild's product classification for the wasm Swift SDK flow does not currently line up with SwiftPM's expectations for com.apple.product-type.tool.swiftpm-test-runner. The minimum reproducer builds the package's umbrella test product through a command plugin and compares --build-system native with --build-system swiftbuild.

Updated minimum reproducer zip: https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/5e90e1ee0202c4969d383ca624eb55725d9942ab/779-swiftpm-test-runner-product-type-linux-2026-06-12.zip

The updated zip preserves the original repro.sh and adds repro-linux-2026-06-12.sh, which is the same reproducer logic adapted for the Linux June 12 snapshot environment.

Expected behavior

com.apple.product-type.tool.swiftpm-test-runner should be treated as a tool/executable product for WebAssembly Swift SDK builds.

For the reproducer, SwiftBuild should surface a usable executable artifact for the synthetic RunnerReproPackageTests test runner, matching the native build-system behavior.

Actual behavior

With the June 12 snapshot and swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm, the native build succeeds and completes the umbrella test product:

succeeded: true
Build of product 'RunnerReproPackageTests' complete!

The SwiftBuild path fails in the synthetic test-runner build with the original failure mode:

error: unable to find sdk 'webassembly'
error: Build failed
succeeded: false

Steps to reproduce

1. Download the updated minimum reproducer zip: https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/5e90e1ee0202c4969d383ca624eb55725d9942ab/779-swiftpm-test-runner-product-type-linux-2026-06-12.zip
2. Unzip it.
3. Enter the extracted 779-swiftpm-test-runner-product-type package directory.
4. Run:

./repro-linux-2026-06-12.sh

The Linux runner writes native.log and swiftbuild.log. It exits 0 when the original issue reproduces and exits 1 if the issue is no longer reproducible.

The only local runner adaptations are the default toolchain path, the default Swift SDK name, and removal of the macOS-only /usr/libexec/PlistBuddy TOOLCHAINS derivation. The original repro.sh is still included unchanged.

Swift Package Manager version/commit hash

Swift Package Manager - Swift 6.5.0-dev

Swift & OS version (output of swift --version ; uname -a)

Swift version 6.5-dev (LLVM 18d2bfb70c14d89, Swift c13d82e5987aecb)
Target: x86_64-unknown-linux-gnu
Build config: +assertions
Linux swift-dev.fugu.katei.dev 6.8.0-94-generic #96-Ubuntu SMP PREEMPT_DYNAMIC Fri Jan  9 20:36:55 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux

[kateinoigakukun]

Minimum reproducer zip is here:

• 779-swiftpm-test-runner-product-type.zip
• Direct zip URL: https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/dd205f748b0108f4a8edc47a84d22af09a5b4f1d/779-swiftpm-test-runner-product-type.zip
• Secret gist index: https://gist.github.com/kateinoigakukun/ba21c654a675032aa77906877c906e53

How to reproduce:

curl -L -O https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/dd205f748b0108f4a8edc47a84d22af09a5b4f1d/779-swiftpm-test-runner-product-type.zip
unzip 779-swiftpm-test-runner-product-type.zip
cd 779-swiftpm-test-runner-product-type
./repro.sh

Environment used to validate these repros:

• Host: macOS 26.5.1 (arm64)
• Toolchain: ~/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2026-05-27-a.xctoolchain
• TOOLCHAINS=org.swift.64202605271a
• swift --version: Apple Swift version 6.5-dev (LLVM 8f81a64f6a8bcf6, Swift 4d0c97fa5b05711)
• Swift SDK: DEVELOPMENT-SNAPSHOT-2026-05-27-a-wasm32-unknown-wasip1
• Each repro.sh uses the explicit snapshot toolchain above, not the global swift on PATH.

Observed on this environment:

• --build-system native: plugin reported succeeded: true and Build of product 'RunnerReproPackageTests' complete!
• --build-system swiftbuild: failed in the synthetic test-runner path with error: unable to find sdk 'webassembly'

[kateinoigakukun]

Verified with the attached minimum reproducer zip from the issue, using the requested June 12 snapshot.

Toolchain:

/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12/usr/bin/swift
Swift version 6.5-dev (LLVM 18d2bfb70c14d89, Swift c13d82e5987aecb)
Target: x86_64-unknown-linux-gnu
Build config: +assertions

Swift SDK: swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm

Issue workdir: /workspace/swiftpm-swiftbuild-issues/swb-jskit-779/
Extracted package/log dir: /workspace/swiftpm-swiftbuild-issues/swb-jskit-779/779-swiftpm-test-runner-product-type/

Local adaptation:

• Left the original repro.sh intact.
• Copied it to repro-linux-2026-06-12.sh.
• Changed only the runner defaults needed for this Linux environment: TOOLCHAIN=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12, SDK=swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm, and removed the macOS-only /usr/libexec/PlistBuddy TOOLCHAINS derivation by leaving TOOLCHAINS unset. The repro logic was otherwise unchanged.

Command:

./repro-linux-2026-06-12.sh > repro-linux-2026-06-12.log 2>&1

Logs:

• /workspace/swiftpm-swiftbuild-issues/swb-jskit-779/779-swiftpm-test-runner-product-type/repro-linux-2026-06-12.log
• /workspace/swiftpm-swiftbuild-issues/swb-jskit-779/779-swiftpm-test-runner-product-type/native.log
• /workspace/swiftpm-swiftbuild-issues/swb-jskit-779/779-swiftpm-test-runner-product-type/swiftbuild.log

Result:

• native: succeeded: true and Build of product 'RunnerReproPackageTests' complete!
• swiftbuild: failed with the original failure mode:

error: unable to find sdk 'webassembly'
error: Build failed
succeeded: false

Conclusion: still reproducible with the requested toolchain/SDK. Leaving this issue open.

[kateinoigakukun]

swiftlang/swift-package-manager#10227