feat: Add macOS support to Swift Package Manager build system

[Saadnajmi]

Summary

Extends the Swift Package Manager (SPM) build system to support macOS, building on the existing iOS/visionOS SPM infrastructure. This enables building React Native as an xcframework with a macOS slice.

Changes

Package.swift

• Added .macOS(.v14) to platforms
• Created React-RCTUIKit as its own SPM module — RCTUIKit needs conditional UIKit (iOS/visionOS) vs AppKit (macOS) linking, which requires it to be a separate target
• Added "RCTUIKit" to React-Core excludedPaths to avoid overlapping sources, and added .reactRCTUIKit as a dependency
• Added conditional linker settings for React-graphics-Apple and React-RCTUIKit:

  .linkedFramework("UIKit", .when(platforms: [.iOS, .visionOS]))
  .linkedFramework("AppKit", .when(platforms: [.macOS]))

• Removed macOS platform paths from exclude lists in reactFabric and reactFabricComponents so macOS-specific C++ files (HostPlatformViewProps, HostPlatformViewEventEmitter, etc.) get compiled

scripts/ios-prebuild/hermes.js

• Ported findMatchingHermesVersion() from Ruby (hermes-utils.rb) to JavaScript — maps react-native-macos version to upstream RN version via peerDependencies['react-native'] in package.json, so Hermes artifacts can be downloaded from Maven
• Ported hermesCommitAtMergeBase() from Ruby — finds the Hermes commit at the merge base with facebook/react-native for main branch builds where no prebuilt artifacts exist (version 1000.0.0)
• Added allowBuildFromSource flag to hermesSourceType() so the nightly fallback behavior isn't broken — only allows BUILD_FROM_HERMES_COMMIT when on main branch with no explicit HERMES_VERSION
• Added ensureMacOSSliceInXCFramework() — after downloading the Hermes tarball from Maven, rebuilds the xcframework to include the macOS slice. The tarball already contains a standalone macOS framework at destroot/Library/Frameworks/macosx/ but it's not included in the xcframework at destroot/Library/Frameworks/universal/. SPM's BinaryTarget requires an xcframework, so we use xcodebuild -create-xcframework to reassemble it with all existing slices plus macOS. This avoids needing any upstream changes to Meta's Hermes publishing pipeline.

scripts/ios-prebuild/setup.js

• Added link('React/RCTUIKit', 'React') for RCTUIKit header linking
• Added macOS view platform header links with both prefixed and unprefixed paths:

  link('ReactCommon/react/renderer/components/view/platform/macos',
       'ReactCommon/react/renderer/components/view');
  link('ReactCommon/react/renderer/components/view/platform/macos',
       'react/renderer/components/view');

  Both are needed because includes use <react/renderer/components/view/MouseEvent.h> which resolves via the non-prefixed search path.

scripts/ios-prebuild/cli.js & types.js

• Added 'macos' to the Platform type and platforms array
• Added 'macOS' to the Destination type and platformToDestination map

How to test locally

cd packages/react-native

# Run setup (downloads deps, runs codegen, links headers, rebuilds Hermes xcframework with macOS slice)
node scripts/ios-prebuild.js -s -f Debug

# Build for macOS
node scripts/ios-prebuild.js -b -f Debug -p macos

# Or build all platforms and compose xcframework
node scripts/ios-prebuild.js -f Debug

Dependencies

• fix(macos): fix compilation errors for macOS target #2868 — fixes pre-existing macOS porting bugs (RCTLinkingManager, RCTCursor, RCTViewComponentView) that cause compilation failures on macOS

Test plan

• node scripts/ios-prebuild.js -s -f Debug completes successfully
• node scripts/ios-prebuild.js -b -f Debug -p macos enters compilation phase
• macOS-specific C++ files (HostPlatformViewProps.cpp, HostPlatformViewEventEmitter.cpp) are compiled
• Hermes xcframework rebuilt with macOS slice after tarball extraction
• Full macOS build completes (blocked on porting fixes in fix(macos): fix compilation errors for macOS target #2868)
• swift package describe --type json outputs valid build graph with macOS targets

🤖 Generated with Claude Code

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