PreviewsSupport

This exposes functions in UIKit and SwiftUI for extracting previews that are not in the swiftinterface for these libraries. The symbols are in the .tbd files, and can be found at link-time.

Modifications to the libraries are needed to make the Swift compiler see these symbols, which is why this is built outside of SPM and linked to the main snapshots package as a binaryTarget.

To build locally, modify Xcode.app/Contents/Developer/Platforms/[iPhoneSimulator/iPhoneOS/MacOSX].platform/Developer/SDKs/iPhoneSimulator.sdk/System/Library/Frameworks/SwiftUI.framework/Modules/SwiftUI.swiftmodule/*.swiftinterface with the following additions at the end of the files:

@available(iOS 17.0, macOS 14.0, *)
public struct ViewPreviewSource {
  public var makeView: @_Concurrency.MainActor () -> any SwiftUI.View
}

and modify Xcode.app/Contents/Developer/Platforms/[iPhoneSimulator/iPhoneOS].platform/Developer/SDKs/iPhoneSimulator.sdk/System/Library/Frameworks/UIKit.framework/Modules/UIKit.swiftmodule/*.swiftinterface with the following additions at the end of the files:

@available(iOS 17.0, macOS 14.0, *)
public struct UIViewPreviewSource {
  public var makeView: @_Concurrency.MainActor () -> UIKit.UIView
}

@available(iOS 17.0, macOS 14.0, *)
public struct UIViewControllerPreviewSource {
  public var makeViewController: @_Concurrency.MainActor () -> UIKit.UIViewController
}

The files in Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/iOSSupport/System/Library/Frameworks/ need to be modified as well for Mac Catalyst support.

In order to link the xcframework without having made the system library modifications, the extensions need to be deleted from the xcframework's .swiftinterface files.