[Sessions] Fix Sendability warnings (#14952)

Author: ncooke3

FirebaseSessions/Sources/Installations+InstallationsProtocol.swift

@@ -16,15 +16,16 @@
 import Foundation
 
 internal import FirebaseInstallations
+internal import FirebaseCoreInternal
 
 protocol InstallationsProtocol: Sendable {
  var installationsWaitTimeInSecond: Int { get }
 
  /// Override Installation function for testing
- func authToken(completion: @escaping (InstallationsAuthTokenResult?, Error?) -> Void)
+ func authToken(completion: @escaping @Sendable (InstallationsAuthTokenResult?, Error?) -> Void)
 
  /// Override Installation function for testing
- func installationID(completion: @escaping (String?, Error?) -> Void)
+ func installationID(completion: @escaping @Sendable (String?, Error?) -> Void)
 
  /// Return a tuple: (installationID, authenticationToken) for success result
  func installationID(completion: @escaping (Result<(String, String), Error>) -> Void)
@@ -35,25 +36,27 @@ extension InstallationsProtocol {
  return 10
  }
 
+ // TODO(ncooke3): Convert o async await ahead of Firebase 12.
+
  func installationID(completion: @escaping (Result<(String, String), Error>) -> Void) {
- var authTokenComplete = ""
- var installationComplete: String?
- var errorComplete: Error?
+ let authTokenComplete = FIRAllocatedUnfairLock<String>(initialState: "")
+ let installationComplete = FIRAllocatedUnfairLock<String?>(initialState: nil)
+ let errorComplete = FIRAllocatedUnfairLock<Error?>(initialState: nil)
 
  let workingGroup = DispatchGroup()
 
  workingGroup.enter()
  authToken { (authTokenResult: InstallationsAuthTokenResult?, error: Error?) in
- authTokenComplete = authTokenResult?.authToken ?? ""
+ authTokenComplete.withLock { $0 = authTokenResult?.authToken ?? "" }
  workingGroup.leave()
  }
 
  workingGroup.enter()
  installationID { (installationID: String?, error: Error?) in
  if let installationID {
- installationComplete = installationID
- } else if let error = error {
- errorComplete = error
+ installationComplete.withLock { $0 = installationID }
+ } else if let error {
+ errorComplete.withLock { $0 = error }
  }
  workingGroup.leave()
  }
@@ -67,9 +70,9 @@ extension InstallationsProtocol {
  completion(.failure(FirebaseSessionsError.SessionInstallationsTimeOutError))
  return
  default:
- if let installationComplete {
- completion(.success((installationComplete, authTokenComplete)))
- } else if let errorComplete {
+ if let installationComplete = installationComplete.value() {
+ completion(.success((installationComplete, authTokenComplete.value())))
+ } else if let errorComplete = errorComplete.value() {
  completion(.failure(errorComplete))
  }
  }