Unable to import OS X frameworks using private headers and header_mappings_dir

[mrackwitz]

What did you do?

Integrated Realm in an OS X target.

What did you expected to happen?

The integrating target would build.

What happened instead?

The generated pod target for Realm itself builds, but it can't be imported. Clang complains about missing headers from the module map:

Realm.framework/Modules/module.modulemap:8:16: error: header 'RLMAccessor.h' not found
        header "RLMAccessor.h"
               ^

DataImporter.swift:20:8: error: could not build Objective-C module 'Realm'
import Realm
       ^

Inspecting the build products and comparing them with the binaries we build ourselves from our Xcode project, it turns out, that the PrivateHeaders symlink in the root directory of the framework bundle is missing. While the actual PrivateHeaders dir exists within Versions/A. My suspicion is that the custom copy files build phase, which ensures to retain the header layout of the header_mappings_dir creates the PrivateHeaders directory in a way Xcode doesn't expect, preventing the automatic creation of the symlink.

So this seems to be an instance of a more general error, which is only relevant for podspecs using header_mappings_dir, a custom module map and private headers, which are explicitly declared in the module map.

CocoaPods Environment

   CocoaPods : 1.0.0
       Xcode : 7.3 (7D175)

Project that demonstrates the issue

https://github.com/realm/realm-cocoa-converter/tree/to-0.102.0-update

[segiddins]

If I understand, this is only an issue for OS X?

[mrackwitz]

Yes, because it fails just because of the missing symlink, which is only present in the framework structure used by OS X.

[segiddins]

Joy 😭

[mrackwitz]

I see two ways how we could solve that:

1. create a private dummy header, which uses Xcode's builtin copy header files build phase
2. create the symlink ourselves by a shell script build phase

Adding a dummy header like in 1. outside of the header_mappings_dir, which would be added to the builtin copy header files build phase isn't allowed, because header files have to be children of the header_mappings_dir.

But it is possible to partially work around that from the podspec as seen below, but this doesn't follow the exact structure and could theoretically break AppStore-compatibility if not already now then possibly in the future.

s.osx.pod_target_xcconfig = {
  'PUBLIC_HEADERS_FOLDER_PATH' => '$(WRAPPER_NAME)/Headers',
  'PRIVATE_HEADERS_FOLDER_PATH' => '$(WRAPPER_NAME)/PrivateHeaders'
}

Note that the PUBLIC_HEADERS_FOLDER_PATH has to be overridden here as well. That's because once the PRIVATE_HEADERS_FOLDER_PATH is overridden, the symlink for the public headers is also not correctly created anymore. That doesn't make any sense to me.

[segiddins]

I guess let's look into a build phase to make the symlinks?