Swift Syntax XCFrameworks

This respository is a proof-of-concept for building packages that depend on swift-syntax (like macros) without having to also build swift-syntax. This is accomplished by prebuilding the libraries of swift-syntax and vending them via the SwiftSyntaxWrapper package.

Using these prebuilt libraries is a way of eliminating the compile time overhead of swift-syntax.

Getting started

Create a new macro package, either from Xcode, or Terminal by typing

swift package init --type macro

Modify the package manifest

Swap swift-syntax dependency for swift-syntax-xcframeworks

Replace

.package(url: "https://github.com/apple/swift-syntax.git", from: "<some version>"),

with

.package(url: "https://github.com/sjavora/swift-syntax-xcframeworks.git", from: "<some version>"),

Update target dependencies with SwiftSyntaxWrapper

Replace

.product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
.product(name: "SwiftCompilerPlugin", package: "swift-syntax")

and

.product(name: "SwiftSyntaxMacrosTestSupport", package: "swift-syntax"),

with

.product(name: "SwiftSyntaxWrapper", package: "swift-syntax-xcframeworks"),

Run the package

The package should now build, tests should run, and the macro in the client should expand correctly.

Compile time comparison

The purpose of this repository is to be able to use swift-syntax while eliminating its compile time. Compare Xcode's build timeline for the default macro package with and without building swift-syntax:

with swift-syntax (18s 72ms)	with swift-syntax-frameworks (2s 28ms)

Measured on a MacBook Pro with M1 Pro and 32 GB RAM, running Xcode 15.0.

Known issues

Warnings

The linker produces a warning about duplicate libraries. This is only visible when building the macro package itself, though, not when using the macro in some other package. This doesn't seem to cause issues in practice.

Clashes with swift-syntax

If your project depends on swift-syntax in any way (e.g., through a third party library), Xcode will fail package resolution due to name clashes. A possible workaround woudl be to rename all the products when building swift-syntax in this repository to avoid such clashes, though that would then require renaming all the imports in files that use SwiftSyntaxWrapper.