fix Sessions build

Author: morganchen12

FirebaseCore/Extension/FIRLibrary.h

@@ -33,7 +33,7 @@ NS_SWIFT_NAME(Library)
 
 /// Returns one or more Components that will be registered in
 /// FirebaseApp and participate in dependency resolution and injection.
-+ (NSArray<FIRComponent *> *)componentsToRegister;
++ (NSArray<FIRComponent *> *NS_SWIFT_SENDING)componentsToRegister NS_SWIFT_UI_ACTOR;
 
 @end
 

FirebaseInstallations/Source/Library/Public/FirebaseInstallations/FIRInstallations.h

@@ -57,8 +57,7 @@ typedef void (^FIRInstallationsTokenHandler)(
  * as the ability to delete it. A Firebase Installation is unique by `FirebaseApp.name` and
  * `FirebaseApp.options.googleAppID` .
  */
-NS_SWIFT_NAME(Installations) NS_SWIFT_SENDABLE
-@interface FIRInstallations : NSObject
+NS_SWIFT_NAME(Installations) NS_SWIFT_SENDABLE @interface FIRInstallations : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;
 

FirebaseSessions/Sources/ApplicationInfo.swift

@@ -67,7 +67,10 @@ final class ApplicationInfo: ApplicationInfoProtocol {
 
   private let networkInformation: NetworkInfoProtocol
   private let envParams: [String: String]
-  nonisolated(unsafe) private let infoDict: [String: Any]?
+
+  // Used to hold bundle info, so the `Any` params should also
+  // be Sendable.
+  private nonisolated(unsafe) let infoDict: [String: Any]?
 
   init(appID: String, networkInfo: NetworkInfoProtocol = NetworkInfo(),
        envParams: [String: String] = ProcessInfo.processInfo.environment,

FirebaseSessions/Sources/FirebaseSessions.swift

@@ -247,18 +247,39 @@ private enum GoogleDataTransportConfig {
     return SessionDetails(sessionId: sessionGenerator.currentSession?.sessionId)
   }
 
+  // This type is not actually sendable, but works around an issue below.
+  // It's safe only if executed on the main actor.
+  private struct MainActorNotificationCallback: @unchecked Sendable {
+    private let callback: (Notification) -> Void
+
+    init(_ callback: @escaping (Notification) -> Void) {
+      self.callback = callback
+    }
+
+    func invoke(notification: Notification) {
+      dispatchPrecondition(condition: .onQueue(.main))
+      callback(notification)
+    }
+  }
+
   func register(subscriber: SessionsSubscriber) {
     Logger
       .logDebug(
         "Registering Sessions SDK subscriber with name: \(subscriber.sessionsSubscriberName), data collection enabled: \(subscriber.isDataCollectionEnabled)"
       )
 
+    // After bumping to iOS 13, this hack should be replaced with `Task { @MainActor in }`
+    let callback = MainActorNotificationCallback { notification in
+      subscriber.onSessionChanged(self.currentSessionDetails)
+    }
+
+    // Guaranteed to execute its callback on the main queue because of the queue parameter.
     notificationCenter.addObserver(
       forName: Sessions.SessionIDChangedNotificationName,
       object: nil,
-      queue: nil
+      queue: OperationQueue.main
     ) { notification in
-      subscriber.onSessionChanged(self.currentSessionDetails)
+      callback.invoke(notification: notification)
     }
     // Immediately call the callback because the Sessions SDK starts
     // before subscribers, so subscribers will miss the first Notification
@@ -270,7 +291,6 @@ private enum GoogleDataTransportConfig {
   }
 
   // MARK: - Library conformance
-
   static func componentsToRegister() -> [Component] {
     return [Component(SessionsProvider.self,
                       instantiationTiming: .alwaysEager) { container, isCacheable in

FirebaseSessions/Sources/Public/SessionsProvider.swift

@@ -17,6 +17,7 @@ import Foundation
 
 // Sessions Provider is the Session SDK's internal
 // interface for other 1P SDKs to talk to.
+@MainActor
 @objc(FIRSessionsProvider)
 public protocol SessionsProvider {
   @objc func register(subscriber: SessionsSubscriber)

FirebaseSessions/Sources/SessionCoordinator.swift

@@ -14,7 +14,7 @@
 
 import Foundation
 
-protocol SessionCoordinatorProtocol {
+protocol SessionCoordinatorProtocol: Sendable {
   func attemptLoggingSessionStart(event: SessionStartEvent,
                                   callback: @escaping (Result<Void, FirebaseSessionsError>) -> Void)
 }
@@ -23,9 +23,11 @@ protocol SessionCoordinatorProtocol {
 /// SessionCoordinator is responsible for coordinating the systems in this SDK
 /// involved with sending a Session Start event.
 ///
-class SessionCoordinator: SessionCoordinatorProtocol {
+final class SessionCoordinator: SessionCoordinatorProtocol {
   let installations: InstallationsProtocol
-  let fireLogger: EventGDTLoggerProtocol
+
+  // TODO: Make this type sendable
+  nonisolated(unsafe) let fireLogger: EventGDTLoggerProtocol
 
   init(installations: InstallationsProtocol,
        fireLogger: EventGDTLoggerProtocol) {

FirebaseSessions/Sources/SessionInitiator.swift

@@ -41,9 +41,9 @@ import Foundation
 ///
 class SessionInitiator {
   let currentTime: () -> Date
-  var settings: SettingsProtocol
-  var backgroundTime = Date.distantFuture
-  var initiateSessionStart: () -> Void = {}
+  let settings: SettingsProtocol
+  private var backgroundTime = Date.distantFuture
+  private var initiateSessionStart: () -> Void = {}
 
   init(settings: SettingsProtocol, currentTimeProvider: @escaping () -> Date = Date.init) {
     currentTime = currentTimeProvider

FirebaseSessions/Sources/Settings/RemoteSettings.swift

@@ -44,7 +44,7 @@ final class RemoteSettings: SettingsProvider, Sendable {
 
   private var sessionsCache: [String: Any] {
     cache.withLock { cache in
-      return cache.cacheContent[RemoteSettings.flagSessionsCache] as? [String: Any] ?? [:]
+      cache.cacheContent[RemoteSettings.flagSessionsCache] as? [String: Any] ?? [:]
     }
   }
 
@@ -65,23 +65,22 @@ final class RemoteSettings: SettingsProvider, Sendable {
       }
     }
 
-      downloader.fetch { result in
-
-        switch result {
-        case let .success(dictionary):
-          self.cache.withLock { cache in
-            // Saves all newly fetched Settings to cache
-            cache.cacheContent = dictionary
-            // Saves a "cache-key" which carries TTL metadata about current cache
-            cache.cacheKey = CacheKey(
-              createdAt: currentTime,
-              googleAppID: self.appInfo.appID,
-              appVersion: self.appInfo.synthesizedVersion
-            )
-          }
+    downloader.fetch { result in
+
+      switch result {
+      case let .success(dictionary):
+        self.cache.withLock { cache in
+          // Saves all newly fetched Settings to cache
+          cache.cacheContent = dictionary
+          // Saves a "cache-key" which carries TTL metadata about current cache
+          cache.cacheKey = CacheKey(
+            createdAt: currentTime,
+            googleAppID: self.appInfo.appID,
+            appVersion: self.appInfo.synthesizedVersion
+          )
+        }
       case let .failure(error):
         Logger.logError("[Settings] Fetching newest settings failed with error: \(error)")
-
       }
     }
   }
@@ -114,7 +113,7 @@ extension RemoteSettingsConfigurations {
 
   func isSettingsStale() -> Bool {
     cache.withLock { cache in
-      return isCacheExpired(cache, time: Date())
+      isCacheExpired(cache, time: Date())
     }
   }
 

FirebaseSessions/Sources/Settings/SettingsDownloadClient.swift

@@ -22,7 +22,8 @@ import Foundation
 #endif // SWIFT_PACKAGE
 
 protocol SettingsDownloadClient: Sendable {
-  func fetch(completion: @Sendable @escaping (Result<[String: Any], SettingsDownloaderError>) -> Void)
+  func fetch(completion: @Sendable @escaping (Result<[String: Any], SettingsDownloaderError>)
+    -> Void)
 }
 
 enum SettingsDownloaderError: Error {
@@ -45,7 +46,8 @@ final class SettingsDownloader: SettingsDownloadClient {
     self.installations = installations
   }
 
-  func fetch(completion: @Sendable @escaping (Result<[String: Any], SettingsDownloaderError>) -> Void) {
+  func fetch(completion: @Sendable @escaping (Result<[String: Any], SettingsDownloaderError>)
+    -> Void) {
     guard let validURL = url else {
       completion(.failure(.URLError("Invalid URL")))
       return