[Macros] Pass a static build configuration to macro implementations #84580
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Introduce the ability to form a `StaticBuildConfiguration` from language options. Add a frontend option `-print-static-build-config` to then print that static build configuration as JSON in a manner that can be decoded into a `StaticBuildConfiguration`. Most of the change here is in sinking the bridged ASTContext queries of language options into a new BridgedLangOptions. The printing of the static build configuration only has a LangOptions (not an ASTContext), so this refactoring is required for printing.
Thread the static build configuration (formed from language options) in to the macro plugin handler, which will serialize it for use in the macro implementation. test this with a simple macro that checks whether a particular custom configuration (set via `-D`) is enabled or not. This required some re-layering, sinking the logic for building a StaticBuildConfiguration from language options down into a new swiftBasicSwift library, which sits on top of the C++ swiftBasic and provides Swift functionality for it. That can be used by the C++ swiftAST to cache the StaticBuildConfiguration on the ASTContext, making it available for other parts of ASTGen.
Now that we have a per-ASTContext StaticBuildConfiguration, reimplement (almost) everything in CompilerBuildConfiguration to sit on top of it. Only canImport requires the full ASTContext, so that gets its own implementation, as does one other operation that can produce an error. Aside from more code sharing, this provides additional validation that the StaticBuildConfiguration we build is complete and accurate.
DougGregor
requested review from
CodaFi,
artemcm,
bnbarham,
hamishknight,
hborla,
rintaro,
slavapestov,
tshortli and
xedin
as code owners
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@swift-ci please test |
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@swift-ci please test |
rintaro
approved these changes
Oct 1, 2025
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Implement support for creating a
StaticBuildConfigurationfromLangOptions. That static build configuration can be printed as JSON to standard output with the new-print-static-build-configfrontend option, and will be passed down to macro implementations so that can perform#if-related evaluations based on the context in which the macro is expanded. To ensure completeness, reseat the existingCompilerBuildConfigurationon top of the createdStaticBuildConfigurationso all#if-handling code in the compiler goes through it.There is a bit of code reshuffling here to establish another layer of Swift library between the C++ Basic and AST libraries. The code to form a
StaticBuildConfigurationexists in this layer, so it can be used without an establishedASTContext. TheASTContextdoes, however, have the ability to build a cache theStaticBuildConfigurationinstance.Tracked by rdar://146868706