error: Multiple commands produce ... x86_64.swiftmodule

Question

I am migrating an old app from swift 3 to swift 4 and got stuck this error:

error: Multiple commands produce '/Users/.../Library/Developer/Xcode/DerivedData/ ... /Debug-iphonesimulator/CompassV3.swiftmodule/x86_64.swiftmodule':
1) Target 'CompassV3' (project 'Void Navigator'): Ditto /Users/.../Library/Developer/Xcode/DerivedData/.../Debug-iphonesimulator/CompassV3.swiftmodule/x86_64.swiftmodule /Users/.../Library/Developer/Xcode/DerivedData/Void_Navigator-bogrvoiumgmhfwcpvocwtssiwgpm/Build/Intermediates.noindex/Void Navigator.build/Debug-iphonesimulator/CompassV3.build/Objects-normal/x86_64/CompassV3.swiftmodule
2) Target 'Outdoor Navigator' (project 'Void Navigator'): Ditto /Users/.../Library/Developer/Xcode/DerivedData/.../Debug-iphonesimulator/CompassV3.swiftmodule/x86_64.swiftmodule /Users/.../Library/Developer/Xcode/DerivedData/Void_Navigator-bogrvoiumgmhfwcpvocwtssiwgpm/Build/Intermediates.noindex/Void Navigator.build/Debug-iphonesimulator/Outdoor Navigator.build/Objects-normal/x86_64/CompassV3.swiftmodule

CompassV3 builds the App

Outdoor navigator is an extension.

Looks like a conflict, but i don't have a clue how to solve it.

The projects are still on swift version 3.

Answer 1

You most likely have two targets with the same product name.

Can you both targets in the project, go to Build Settings and check the values for "Product Module Name" in the Packaging section?