Linking only embedded framework with other dynamic framework fails when build & run on device

Question

tl;dr

Linking your embedded framework with other framework and don't link other framework with your app cause required code signature missing when Build & Run on device.

description:

Setup:

My setup is pretty simple (Swift 2.3 & Xcode Xcode 8.0; Build version 8S162m):

• Using Carthage (0.17.2) I have build Other.framework with xcodebuild 8.0 and TOOLCHAINS=com.apple.dt.toolchain.Swift_2_3 carthage build --platform iOS
• MyApp has embeded My.framework.
• The app and the framework projects are under one Xcode workspace.
• I hade linked Other.framework to My.framework ONLY (that means, MyApp is not linked to Other.framework at all). The point here is that, MyApp does not need to use Other.framework API.

Problem:

Everything seems to work fine, until I Build & Run the app on the device. The app launched and than the process is aborted with the following Xcode error:

dyld: Library not loaded: @rpath/Other.framework/Other  
  Referenced from: /private/var/containers/Bundle/Application/DCF0331F-FF23-43CF-AE79-B3857D5A6EE3/MyApp.app/Frameworks/My.framework/My  
  Reason: no suitable image found.  Did find:  
  /private/var/containers/Bundle/Application/DCF0331F-FF23-43CF-AE79-B3857D5A6EE3/MyApp.app/Frameworks/My.framework/Frameworks/Other.framework/Other: required code signature missing for '/private/var/containers/Bundle/Application/DCF0331F-FF23-43CF-AE79-B3857D5A6EE3/MyApp.app/Frameworks/My.framework/Frameworks/Other.framework/Other'  

I have checked the signature of Other.framework and it looked OK to me. Moreover,

Solution (workaround)

Link MyApp with Other.framework. Horrible... This feels broken.

Linking the very same binary Other.framework to MyApp and solving the issue this way, points out, the Other.framework is built OK and able to be re-signed correctly. Possibly, nothing to do with Carthage.

NOTE: There is a similar problem iOS 8+ framework with nested embedded framework, however, mine has slightly other reason.

Answer 1

Discussing this issue on the Carthage github page, it's become clear that the workaround mentioned in the question, is actually an expected behaviour:

Carthage doesn't support nested frameworks.

Nesting frameworks doesn't let you reuse those frameworks. For instance, if A.framework and B.framework both depend on Other.framework, then neither of them can nest Other.framework—otherwise you might end up with 2 different versions, and the correct one might not be chosen at runtime.

The correct way to do this is to list it as a dependency, but link it into the app target.

Full discussion: Linking only embedded framework with other dynamic framework fails when build & run on device: "required code signature missing"

This was unclear from the README, so I raised another issue, requesting to update the documentation:

Update to README: Linking dynamic frameworks to embedded frameworks requires as well linking them to the app target #1427

This is resolved and closed in the scope of the PR:

#1427 README upd: link dependencies from embedded frameworks to the app target