SwiftUI Preview + Swift Packages Break App

Question

Created Jul ’24

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I have a multi-platform app with the SwiftUI code a separate Swift Package. Any Views with SwiftUI Previews break the compilation of the app. Here's the error message I get in Xcode:

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ld: warning: Could not parse or use implicit file '/Applications/Xcode-beta.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/System/Library/Frameworks/SwiftUICore.framework/SwiftUICore.tbd': cannot link directly with 'SwiftUICore' because product being built is not an allowed client of it
Undefined symbols for architecture arm64_32:
  "(extension in SwiftUI):DeveloperToolsSupport.Preview.init(_: Swift.String?, traits: DeveloperToolsSupport.PreviewTrait<DeveloperToolsSupport.Preview.ViewTraits>..., body: @Swift.MainActor @Sendable () -> SwiftUI.View) -> DeveloperToolsSupport.Preview", referenced from:
      static BitnessViews.$s12BitnessViews33_ABDBADF565C741E50A2A5746CE94FCD9Ll7PreviewfMf_15PreviewRegistryfMu_.makePreview() throws -> DeveloperToolsSupport.Preview in BitnessViews.o
ld: symbol(s) not found for architecture arm64_32
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Could not parse or use implicit file '/Applications/Xcode-beta.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/System/Library/Frameworks/SwiftUICore.framework/SwiftUICore.tbd': cannot link directly with 'SwiftUICore' because product being built is not an allowed client of it

Undefined symbol: (extension in SwiftUI):DeveloperToolsSupport.Preview.init(_: Swift.String?, traits: DeveloperToolsSupport.PreviewTrait<DeveloperToolsSupport.Preview.ViewTraits>..., body: @Swift.MainActor @Sendable () -> SwiftUI.View) -> DeveloperToolsSupport.Preview

Linker command failed with exit code 1 (use -v to see invocation)

Any thoughts as to what might be going on here?

Boost

Answer 1

Developer Tools Engineer OP

Apple

Jul ’24

Sorry you're hitting this error, this sounds like something we'll need more diagnostics to figure out what's going on.

Could you please file a bug report and attach your preview diagnostics?

Steps to generate helpful diagnostics:

Download and install the logging profile on all devices involved. Instructions and profiles are available here: https://developer.apple.com/bug-reporting/profiles-and-logs/?name=swift
Reproduce the issue
Click the "Diagnostics" button in the error banner in Previews' Canvas area (or if the banner is missing you can use the menu: Editor > Canvas > Diagnostics)
In the sheet that appears, click "Generate Report" in the bottom left of the sheet
Attach (or make from the folder) the resulting zip file to the bug report (will be named something like previews-diagnostics-0123456789.zip)
Generate the sysdiagnose(s) and attach those too

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