Summary:
This PR adds support for using SonarKit clients in Swift apps. Fixes#13, fixes#87
1. Swift can't import Obj-C modules which have C++ headers. For this reason, we use SonarKit as an Obj-C++ wrapper around Sonar, which is written in C++. Due to search path misconfiguration, trying to import SonarKit into a Swift project would import `xplat/Sonar/SonarPlugin.h` instead of `iOS/SonarKit/SonarPlugin.h`, which caused `file not found` errors for C++ stdlib imports like #28 because new projects don't have their search paths set up correctly.
2. The network and layout plugins have C++ definitions (struct methods, classes) in some of their headers. This causes the compiler to get confused for Swift projects, because it only supports importing Objective-C files in umbrella headers, meaning that the `SonarKit` won't build.
1. I updated the `HEADER_SEARCH_PATHS` of SonarKit.podspec's build configuration to include `${PODS_ROOT}/Headers/Private/SonarKit/**` first, which alleviates the search path issue. The Obj-C `Sample` project seems to have worked around this by including a hardcoded `${PODS_ROOT}/SonarKit/**` search path in the pbxproj, which is why Sample works but new projects (like those referenced in #28) don't. I removed this since it's no longer necessary.
2. I added a `SampleSwift` app to demonstrate using Sonar with a Swift project.
3. Because the Podfiles for `Sample` and `SampleSwift` referenced podspecs using `:podspec` instead of a concrete version, Cocoapods wouldn't copy local header files (instead, it downloads them from the source). To enable local development of these sample apps using `:path`, I added a symlink to SonarKit.podspec in the root of the directory.
4. I changed SonarKit.podspec to use a tag-based `source`, since v0.0.1 pulls from the master branch of this repo.
The layout and network plugins still don't work with Swift - in order to fix this, we'll need to work on extracting the C++ out of their headers and writing Obj-C++ wrappers for them. I decided to push this off to a later PR since this one is quite large already.
This means that we need to be able to `import SonarKit` without importing all the network/layout plugin headers. In order to make this work, I made "SonarKit/Core" the spec's `default_subspecs`.
priteshrnandgaonkar, let me know if you have any thoughts on this implementation. You can verify that the SampleSwift app works by checking out this branch, `pod install`ing in the SampleSwift directory, and building it :)
Pull Request resolved: https://github.com/facebook/Sonar/pull/106
Reviewed By: jknoxville
Differential Revision: D8890010
Pulled By: priteshrnandgaonkar
fbshipit-source-id: 449305bcc5cbeb5787c23f51b1ecb80a5cbdad32
