[Firestore] Combine Firestore and FirestoreSwift into a single module

[ncooke3]

This is experimental and not for merging.

Context

• Merged the FirestoreSwift pod into the Firestore pod

  • This merge led to a problem we haven't seen before. We had an xcframework containing a .swiftmodule (FirebaseFirestore) exporting API from a source Swift target (SharedSwift). The issue is that FirebaseFirestore's .swiftmodule file is built with BUILD_LIBRARY_FOR_DISTRIBUTION=YES (this is required; see https://forums.developer.apple.com/thread/125646), but is trying to export a type (see the FirebaseSharedSwift's FirebaseData(En|De)Coder types in Firestore's Swift source) from a Swift module (FirebaseSharedSwift) that isn't built BUILD_LIBRARY_FOR_DISTRIBUTION=YES (this is because SPM does not offer a way to set BUILD_LIBRARY_FOR_DISTRIBUTION=YES for source targets). The issue surfaces during the linking phase and materializes in a several undefined symbol errors from the FirebaseSharedSwift module (as ABI stable symbols cannot be found). The solution is to convert FirebaseSharedSwift's release distribution from source to binary, since binaries give allows us to set BUILD_LIBRARY_FOR_DISTRIBUTION=YES.

• Built an xcframework from the combined Firestore pod

  Expand to see the `zip-builder` invocation

  sudo xcode-select -s /Applications/Xcode_13.3.1.app 
  swift run --package-path ReleaseTooling zip-builder \                                                                                              (1.181s) 
    --disable-build-dependencies \
    --disable-carthage-version-check \
    --no-dynamic \
    --keep-build-artifacts \
    --no-update-pod-repo \
    --pods FirebaseFirestore \
    --local-podspec-path /Users/nickcooke/Developer/firebase-ios-sdk/
  

• Manually tested SPM integration with the Firestore QS

Remaining Work

• Update QS to handle this
• Decide what to do to existing FirestoreSwift changelog
• Add changelog entry for this new change

[github-actions]

✅  No API diff detected

Commit: 08bb33e
Last updated: Fri May 26 11:18 PDT 2023
View workflow logs & download artifacts

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[ncooke3]

Checkpoint– 995e536 has all tests except expected QS failure.

[ncooke3]

At this point, the only remaining FirestoreSwift mentions are as followed.

➜  firebase-ios-sdk git:(nc/firestore-flatten) 
‣ git grep 'FirestoreSwift'
CoreOnly/NOTICES:FirebaseFirestoreSwift
FirebaseCore/CHANGELOG.md:  Podfile like `pod 'FirebaseFirestoreSwift', '~> 7.0-beta'`.
Firestore/CHANGELOG.md:  `FirebaseFirestoreSwift` module dependency to your build target (#9426).
Firestore/Swift/CHANGELOG.md:- [added] **Breaking change:** `FirebaseFirestoreSwift` has exited beta and is
Firestore/Swift/CHANGELOG.md:- [changed] FirebaseFirestoreSwift now requires a minimum iOS version of 11 for

[ncooke3]

Closing in favor of #11806