Swift Macro Test - build issue - when it depends on the universal plugin

[chiragramani]

When swift_test depends on the universal plugin, build fails with the following error:

examples/xplatform/macros/StringifyMacroTests.swift:18:8: error: missing required module 'SwiftCompilerPlugin'
import StringifyMacroPlugin
       ^
examples/xplatform/macros/StringifyMacroTests.swift:18:8: error: missing required module 'SwiftCompilerPlugin'
import StringifyMacroPlugin

Repro bazel test //examples/xplatform/macros:stringify_macro_test

swift_test(
    name = "stringify_macro_test",
    srcs = ["StringifyMacroTests.swift"],
    deps = [
        ":stringify_macro_universal", // build is successful when it depends on the ":stringify_macro"
        "@SwiftSyntax",
        "@SwiftSyntax//:SwiftSyntaxBuilder",
        "@SwiftSyntax//:SwiftSyntaxMacros",
    ],
)

We can fix this by adding "@SwiftSyntax//:SwiftCompilerPlugin", as one of the deps, but then we see the following errors:

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
ld: warning: duplicate -rpath '/usr/lib/swift' ignored
ld: warning: ignoring file 'bazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/external/SwiftSyntax/libSwiftSyntaxMacroExpansion.a[2](MacroExpansion.swift.o)': found architecture 'x86_64', required architecture 'arm64'
ld: warning: ignoring file 'bazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/external/SwiftSyntax/libSwiftCompilerPlugin.a[2](CompilerPlugin.swift.o)': found architecture 'x86_64', required architecture 'arm64'
ld: warning: ignoring file 'bazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/external/SwiftSyntax/libSwiftBasicFormat.a[5](BasicFormat+Extensions.swift.o)': found architecture 'x86_64', required architecture 'arm64'
ld: warning: ignoring file 'bazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/external/SwiftSyntax/libSwiftBasicFormat.a[4](Trivia+FormatExtensions.swift.o)': found architecture 'x86_64', required architecture 'arm64'
ld: warning: ignoring file 'bazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/external/SwiftSyntax/libSwiftBasicFormat.a[3](SyntaxProtocol+Formatted.swift.o)': found architecture 'x86_64', required architecture 'arm64'
ld: warning: ignoring file

The compilation on darwin_arm64, has an -Ipath pointing to x86_64 directory

-Ibazel-out/darwin_arm64-fastbuild/bin/external/SwiftSyntax \

-Ibazel-out/darwin_arm64-fastbuild/bin/examples/xplatform/macros \

-Ibazel-out/darwin_x86_64-fastbuild-ST-6f7624269444/bin/examples/xplatform/macros

[keith]

Yea you should depend on the non-universal one for your test bundle. If you build a universal test bundle then you'll get the universal plugin for free as well.

I think the core issue here is that we're just propagating everything from the universal plugin impl https://github.com/bazelbuild/rules_swift/blob/61df2d5e9f549fa47bfe38fae7829408d16bafed/swift/swift_compiler_plugin.bzl#L287-L291 when what the swift_test expects is just the current arch it's building for. We could probably fix that with some custom logic here https://github.com/bazelbuild/rules_swift/blob/61df2d5e9f549fa47bfe38fae7829408d16bafed/swift/internal/swift_binary_test.bzl#L284-L292 but I would recommend just depending on the main plugin instead (maybe we should make swift_test depending on the universal plugin impossible).