`swift build` failed when macro and target depend on the same C target

[qazyn951230]

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

When marco and target depend on the same C target, running swift build will produce a redefinition of module error.

A minimal example can be found here. The project structure is as follows:

• CLib
• MyLib
  • CLib
  • MyMacro
• MyMacro
  • CLib

MyLib and MyMacro only import CLib and have no other code.

Expected behavior

Compiled successfully.

Actual behavior

$ swift build
[1/1] Planning build
Building for debugging...
error: emit-module command failed with exit code 1 (use -v to see invocation)
<REDACTED>/CLib-tool.build/module.modulemap:1:8: error: redefinition of module 'CLib'
module CLib {
       ^
<REDACTED>/CLib.build/module.modulemap:1:8: note: previously defined here
module CLib {
       ^
<REDACTED>/CLib-tool.build/module.modulemap:1:8: error: redefinition of module 'CLib'
module CLib {
       ^
<REDACTED>/CLib.build/module.modulemap:1:8: note: previously defined here
module CLib {
       ^

Steps to reproduce

1. git clone https://github.com/qazyn951230/MacroTest.git
2. cd MacroTest
3. swift build

Swift Package Manager version/commit hash

6.1.0

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

Swift 6.1 from Xcode 16.3

$ swift --version
swift-driver version: 1.120.5 Apple Swift version 6.1 (swiftlang-6.1.0.110.21 clang-1700.0.13.3)
Target: arm64-apple-macosx15.0

[dschaefer2]

I see. We are picking up the dependencies from the macros and plugins and hooking them up. That's why we get them twice. I'll fix up the algorithm.

[qazyn951230]

@dschaefer2 I'm glad you fixed it. Should it be cherry-picked into the branch "release/6.2" since it's a bug fix?

[dschaefer2]

Fixed by #8472

[dschaefer2]

@qazyn951230 We'll be merging all changes in main to release/6.2 for the next few weeks. Just waiting to see if we get an auto merger first.