[5/x] Fix pre-built library evolution and testability

[andrewchang-bird]

Stack

📚 #266 [6/x] Update example projects to use 0.19.1
📚 #265 ← [5/x] Fix support for Swift library evolution
📚 #264 [4/x] Fix configurator relative path handling
📚 #263 [3/x] Fix package manager integrations
📚 #261 [2/x] Archive supporting sources in release workflow
📚 #260 [1/x] Fix CLI archiving and distribution

Overview

Library Evolution

Module stability is currently broken despite enabling the BUILD_LIBRARIES_FOR_DISTRIBUTION build setting which prevents using an “old” version of Mockingbird.framework if it hasn’t been compiled for the current toolchain and Swift version. After some investigation, it’s due to a known issue since Xcode 11.2 (SR-14195):

If a module is built with BUILD_LIBRARIES_FOR_DISTRIBUTION and contains a public type with the same name as the module itself, clients will fail to import the module. (19481048) (FB5863238)

Workaround: Rename either the type or the module to remove the conflict.

Specifically, Mockingbird returns an XCTest.XCTestExpectation for asynchronous testing which is ambiguous in the module interface since XCTest itself exports a class named XCTest. To fix the issue, this PR avoids referencing XCTest symbols in the Swift module interface by bridging them from Objective-C.

A side effect of the test expectation changes is that the asynchronous verification API is improved:

// Old
let expectation = eventually {
  verify(bird.canFly).wasCalled()
  verify(bird.fly()).wasCalled()
}
wait(for: [expectation], timeout: 1.0)

// New
eventually {
  verify(bird.canFly).wasCalled()
  verify(bird.fly()).wasCalled()
}
waitForExpectations(timeout: 1.0)

Testability

The release version is set to strip debug symbols which prevents testable imports of Mockingbird. This explicitly sets COPY_PHASE_STRIP to NO for both Carthage and CocoaPods.

Fixes #242

Test Plan

Archiving the framework with Xcode 13.0 / Swift 5.5 and compiling it against the Xcode 13.2 / Swift 5.5.2 toolchain no longer produces errors.