Header not found when adding Themis as dependency in a new development cocoapod

[popaaaandrei]

Issue description

I am adding Themis as a dependency in a new development cocoapod like this:
s.dependency 'themis', '0.10.3' (also tried with s.dependency 'themis/themis-openssl', '0.10.3')

I have 2 errors when trying to build the project:

• 'soter/soter_error.h' file not found inside themis/themis_error.h line 31 (#include <soter/soter_error.h>)
• and obviously Could not build Objective-C module 'themis' where I am importing themis

Environment info

OS: iOS 10
Cocoapods 1.5.3
Themis version: 0.10.0/2/3

Installation way: via package manager
Crypto provider: OpenSSL I think

[vixentael]

Seems that this gonna be a long journey :)

1. There are existing pods that use Themis as dependency pod:

https://github.com/cossacklabs/acra/blob/master/acrawriter.podspec

But note two things:

• this is a cocoapod made from objc code
• it sets up 'HEADER_SEARCH_PATHS' => '"${PODS_ROOT}/themis/src" "${PODS_ROOT}/themis/src/wrappers/themis/Obj-C"' to fix header-searching issue.

So, first issue is fixed just to setting up correct HEADER_SEARCH_PATHS so Themis could find all its files.

2. However, if you do that, you will experience next problem. If you try to create Swift framework, Xcode will try to build Swift module from objective-c files. And this is the place where rabbit hole starts.

3. I've played a bit myself with our Swift example project in vxtl/ios-header branch. Original example is written in Swift and uses Bridging header to import Themis file. Bridging header contains very simple #import <objcthemis/objcthemis.h> that imports all needed headers, and everything is working fine.

4. Unfortunately, when building Swift frameworks (or CocoaPod) that uses ObjC code, you can't use Bridging headers (because Apple said so), but should use modular frameworks instead.

5. You can simulate this behavior taking above mentioned example project and write import themis inside Swift code. This makes Xcode to build Swift modular framework, and fail.

First, you see typical Xcode error message like

because of include non-modular header inside framework error:

People say, that it's a typical error, when private headers are exposed into .h files. For example, AFNetworking solved similar issue just by moving some headers into .m files.

In Themis we can't hide all headers (although this was the first thing I tried to do in objc wrapper, results can be found in vxtl/ios-header branch), but internal structure of Themis (themis, soter, openssl) has exposed headers and it's rather complicated to change it.

6. iOS gurus suggest to build modular framework, exposing required headers in custom module.modulemap (I found good blogposts about modular frameworks, challenges in building them, more challenges and more advice and even more).

So now I'm trying to add all required headers to the modulemap.

Issue I face right now is how to support complex multi-level folder structure in modulemap, because it looks like only "flat" files are supported:

[vixentael]

In Themis we can't hide all headers (although this was the first thing I tried to do in objc wrapper, results can be found in vxtl/ios-header branch)

it actually worked 😱

See updated Themis iOS wrapper code in #415, see new temporary Themis.podspec 0.10.4 in #416.

Upon confirmation, successful testing and merging, I'll push podspec officially.

[popaaaandrei]

Confirm that works for me. Thank you!

[vixentael]

@popaaaandrei themis 0.10.4 is public now :)