Error when using --explicit-target-dependency-import-check=error with --enable-experimental-prebuilts

[vsarunas]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

The #8798 was closed, but it does not work.

Expected behavior

Build should exit with success error code.

Actual behavior

Build exits with 1, causing false CI check failures.

Steps to reproduce

git clone https://github.com/swiftlang/swift-testing -b 6.1.1
cd swift-testing
rm -rf .build
DEVELOPER_DIR=/Applications/Xcode-26.0.0-Beta.3.app/Contents/Developer swift build --explicit-target-dependency-import-check=error --enable-experimental-prebuilts --quiet
[1/1] Planning build
error: Target TestingMacrosTests imports another target (SwiftSyntaxBuilder) in the package without declaring it a dependency.
error: Target TestingMacros imports another target (SwiftCompilerPlugin) in the package without declaring it a dependency.
Building for debugging...
[1/1] Write swift-version-1160FFD79CDEE07D.txt
Build complete! (1.62s)

The same with Beta 4:

DEVELOPER_DIR=/Applications/Xcode-26.0.0-Beta.4.app/Contents/Developer swift build --explicit-target-dependency-import-check=error --enable-experimental-prebuilts --quiet
[1/1] Planning build
error: Target TestingMacrosTests imports another target (SwiftSyntaxMacroExpansion) in the package without declaring it a dependency.
error: Target TestingMacros imports another target (SwiftCompilerPlugin) in the package without declaring it a dependency.
Building for debugging...
[1/1] Write swift-version-1160FFD79CDEE07D.txt
Build complete! (1.40s)

Swift Package Manager version/commit hash

No response

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

swift-driver version: 1.127.10 Apple Swift version 6.2 (swiftlang-6.2.0.14.8 clang-1700.3.14.6)

[dschaefer2]

Yeah, #8798 was improperly closed. There is a gap between when Xcode betas are published until we can get the prebuilts made available and this only happens when prebuilts are available.

This is a tricky one since we are replacing the dependencies with compile flags that bring in the dependencies. They do not appears as target dependencies since we don't want them built.

It kinda opens up the question of the validity of this check when using prebuilt Swift modules. Have to think about this one.