[SwiftBuild] Exclude implicit executable plugin tools from package product reporting in SwiftPM

[kateinoigakukun]

Description

Follow-up from #773.

SwiftPM currently surfaces implicit executable products that exist only to satisfy build-tool plugin dependencies as if they were ordinary package products. That pollutes package product reporting and can cause aggregate destination builds to try to build host-only plugin helper executables as wasm artifacts.

The minimum reproducer targets the related command-plugin built-artifact selection path. It has a small Runner library with a test target and a DumpTests command plugin that asks SwiftPM to build the umbrella test product RunnerReproPackageTests. With SwiftBuild, that request fails while the native/control build succeeds.

Expected behavior

Internal helper executables used by plugins should remain implementation details and should not be serialized or reported as user-facing package products.

In this reproducer:

• --build-system native dump-tests should build the umbrella test product and report the built test runner artifact.
• --build-system swiftbuild dump-tests should do the same, without looking for a non-existent SDK named webassembly.
• Command plugin flows should still find the artifacts they need.

Actual behavior

Using the requested 2026-06-12 Linux snapshot and swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm SDK:

• --build-system native exits 0 and reports succeeded: true and Build of product 'RunnerReproPackageTests' complete!.
• --build-system swiftbuild exits 1 and reports:

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

Steps to reproduce

Download the existing minimum reproducer zip from the issue comment:

https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/49009ab10eede7013f079a9efc54114912dd589b/775-plugin-product-reporting.zip

Then run:

unzip 775-plugin-product-reporting.zip
cd 775-plugin-product-reporting

env \
  TOOLCHAIN=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12 \
  TOOLCHAINS=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12 \
  SWIFT_SDK_ID=swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm \
  bash ./repro.sh

The script itself was not edited for the Linux verification. The environment overrides select the requested Linux Swift toolchain and SDK instead of the script's macOS/2026-05-27 defaults.

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:

• 775-plugin-product-reporting.zip
• Direct zip URL: https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/49009ab10eede7013f079a9efc54114912dd589b/775-plugin-product-reporting.zip
• Secret gist index: https://gist.github.com/kateinoigakukun/ba21c654a675032aa77906877c906e53

How to reproduce:

curl -L -O https://gist.githubusercontent.com/kateinoigakukun/ba21c654a675032aa77906877c906e53/raw/49009ab10eede7013f079a9efc54114912dd589b/775-plugin-product-reporting.zip
unzip 775-plugin-product-reporting.zip
cd 775-plugin-product-reporting
./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 on the same request with error: unable to find sdk 'webassembly'

[kateinoigakukun]

Verification with the minimum reproducer from the gist zip:

• Workdir: /workspace/swiftpm-swiftbuild-issues/swb-jskit-775/775-plugin-product-reporting
• Swift: /home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12/usr/bin/swift
• Swift version: Swift version 6.5-dev (LLVM 18d2bfb70c14d89, Swift c13d82e5987aecb), target x86_64-unknown-linux-gnu
• Swift SDK: swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm
• Reproducer script: original repro.sh; no script edits
• Invocation adaptation: passed TOOLCHAIN=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12, TOOLCHAINS=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12, and SWIFT_SDK_ID=swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm so the macOS hardcoded default toolchain/SDK in the script would use the requested Linux snapshot and SDK.

Command run:

env TOOLCHAIN=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12 TOOLCHAINS=/home/ubuntu/.local/share/swiftly/toolchains/main-snapshot-2026-06-12 SWIFT_SDK_ID=swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm bash ./repro.sh > repro.log 2>&1

Result:

• Native/control path: exit code 0; succeeded: true; Build of product 'RunnerReproPackageTests' complete!
• SwiftBuild path: exit code 1; succeeded: false
• SwiftBuild failure:

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

Conclusion: still reproducible with the requested 2026-06-12 Linux snapshot and swift-DEVELOPMENT-SNAPSHOT-2026-06-12-a_wasm. Leaving this issue open.

Logs:

• repro.log
• native.log
• swiftbuild.log
• adaptation-notes.md

[kateinoigakukun]

swiftlang/swift-package-manager#10223