Prepare for Swift 6 Language Mode (#11)

* Fix Swift 6 language mode issues.

* Enable strict concurrency checking, momentarily.

* Add a comment.

* Revert an unwanted change.

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:5.10
 
 import PackageDescription
 

Sources/Etcetera/BackgroundTasks/BackgroundTask.swift

@@ -13,7 +13,7 @@ private typealias Internals = UnsupportedBackgroundTask
 #endif
 
 /// A cross-platform wrapper for requesting background execution time.
-public final class BackgroundTask: @unchecked Sendable {
+public final class BackgroundTask: Sendable {
 
  /// Convenience for initializing a task with a default expiration handler.
  ///

Sources/Etcetera/BackgroundTasks/UnsupportedBackgroundTask.swift

@@ -9,7 +9,7 @@
 import UIKit
 
 /// For environments that do not support background tasks.
-final class UnsupportedBackgroundTask: @unchecked Sendable {
+final class UnsupportedBackgroundTask: Sendable {
 
  @MainActor static func start() -> UnsupportedBackgroundTask? {
  return nil

Sources/Etcetera/BackgroundTasks/iOSBackgroundTask.swift

@@ -11,7 +11,7 @@
 import UIKit
 
 /// A quality-of-life wrapper around requesting iOS background execution time.
-class iOSBackgroundTask: @unchecked Sendable {
+final class iOSBackgroundTask: Sendable {
 
  /// Convenience for initializing a task with a default expiration handler.
  ///
@@ -50,7 +50,12 @@ class iOSBackgroundTask: @unchecked Sendable {
 
  init() {}
 
- private var taskId: UIBackgroundTaskIdentifier = .invalid
+ private var taskId: UIBackgroundTaskIdentifier {
+ get { _taskId.current }
+ set { _taskId.current = newValue }
+ }
+
+ private let _taskId = Protected(UIBackgroundTaskIdentifier.invalid)
 
 }
 

Sources/Etcetera/Foundation/Locking.swift

@@ -11,7 +11,7 @@ import os.lock
 /// A high-performance lock supported by all Apple platforms.
 ///
 /// This lock is **not** recursive.
-public final class Lock: Sendable {
+public final class Lock: @unchecked Sendable {
 
  /// See WWDC 2016 Session 720. Using C struct locks like `pthread_mutex_t`
  /// or `os_unfair_lock` directly from Swift code is discouraged because of
@@ -64,9 +64,18 @@ public final class Protected<T>: @unchecked Sendable {
  }
 }
 
+extension Protected {
+
+ /// Convenience initializer that defaults to `nil`.
+ public convenience init<O>() where T == Optional<O> {
+ self.init(nil)
+ }
+
+}
+
 /// A dictionary-like object that provides synchronized read/writes via an
 /// underlying `Protected` value.
-public final class ProtectedDictionary<Key: Hashable, Value> {
+public final class ProtectedDictionary<Key: Hashable, Value>: Sendable {
 
  private let protected: Protected<[Key: Value]>
 

Sources/Etcetera/Foundation/NotificationObserver.swift

@@ -18,7 +18,7 @@ import Foundation
 /// and trust ARC to release the observer at the appropriate time, which will
 /// remove all observations. This assumes, of course, that all blocks passed to
 /// `when(_:perform:)` do not strongly capture `self`.
-public class NotificationObserver: NSObject, @unchecked Sendable {
+public final class NotificationObserver: NSObject, Sendable {
 
  // MARK: - Typealiases
 
@@ -35,8 +35,18 @@ public class NotificationObserver: NSObject, @unchecked Sendable {
  /// The target queue for all observation callbacks.
  private let queue: OperationQueue
 
- /// The (optional) target object to be used when observing notifications.
- private weak var object: AnyObject?
+ /// The target object to be used when observing notifications.
+ private var object: AnyObject? {
+ get { _object.access {
+ $0.object
+ }}
+ set { _object.access {
+ $0.object = newValue
+ }}
+ }
+
+ /// The backing storage for `object`.
+ private let _object: Protected<WeakReferencingBox>
 
  /// A tote bag of observation tokens.
  private let tokens = Protected<[Token]>([])
@@ -55,7 +65,7 @@ public class NotificationObserver: NSObject, @unchecked Sendable {
  ///
  /// - parameter queue: The target queue for all observation callbacks.
  public init(object: AnyObject? = nil, queue: OperationQueue = .main) {
- self.object = object
+ self._object = Protected(WeakReferencingBox(object: object))
  self.wasInitializedWithTargetObject = (object != nil)
  self.queue = queue
  }
@@ -118,4 +128,14 @@ public class NotificationObserver: NSObject, @unchecked Sendable {
  return when(name, perform: { _ in block() })
  }
 
+ // MARK: - Nested Types
+
+ private final class WeakReferencingBox {
+ weak var object: AnyObject?
+
+ init(object: AnyObject? = nil) {
+ self.object = object
+ }
+ }
+
 }

Sources/Etcetera/Foundation/ProcessInfo.swift

@@ -37,14 +37,16 @@ extension ProcessInfo {
  /// or:
  ///
  /// if ProcessInfo.Argument.resetCachesOnLaunch.isEnabled { ... }
- public struct Argument: RawRepresentable, ExpressibleByStringLiteral {
+ public struct Argument: RawRepresentable, ExpressibleByStringLiteral, Sendable {
 
  /// Supply your own "-com.domain.MyApp." prefix which must be present in
  /// all the custom arguments defined in your target's scheme editor.
- public static var commonPrefix: String {
+ public static nonisolated var commonPrefix: String {
  get { _commonPrefix.current }
  set { _commonPrefix.current = newValue }
  }
+
+ /// Backing storage for `commonPrefix`.
  private static let _commonPrefix = Protected<String>("")
 
  /// Required by `RawRepresentable`.
@@ -62,23 +64,26 @@ extension ProcessInfo {
  return ProcessInfo.isArgumentEnabled(self)
  }
 
+ /// Required by `RawRepresentable`.
  public init(rawValue: String) {
  self.rawValue = rawValue
  }
 
+ /// Required by `RawRepresentable`.
  public init(stringLiteral value: String) {
  self.rawValue = value
  }
+
  }
 
  /// - returns: Returns `true` if `argument` is found among the arguments.
- public static func isArgumentEnabled(_ argument: Argument) -> Bool {
+ public static nonisolated func isArgumentEnabled(_ argument: Argument) -> Bool {
  let string = Argument.commonPrefix + argument.rawValue
  return processInfo.arguments.contains(string)
  }
 
  /// Returns `true` if the app is running as a test runner for unit tests.
- public static var isRunningInUnitTests: Bool {
+ public static nonisolated var isRunningInUnitTests: Bool {
  processInfo.environment["XCTestConfigurationFilePath"] != nil
  }
 

Sources/Etcetera/Global/Global.swift

@@ -41,7 +41,7 @@
  /// directly when declaring an `@Global`-wrapped property. Instead, Global
  /// wrappers are regularly initialized via init methods declared in
  /// extensions (see the README for details).
- public init(initializer: @MainActor @escaping (Container) -> Wrapped) {
+ public init(initializer: @MainActor @escaping @Sendable (Container) -> Wrapped) {
  resolver = {
  Container.shared.resolveInstance(via: initializer)
  }
@@ -62,7 +62,7 @@
  /// directly when declaring an `@Global`-wrapped property. Instead, Global
  /// wrappers are regularly initialized via init methods declared in
  /// extensions (see the README for details).
- public init<InstanceIdentifier: Hashable>(instanceIdentifier: InstanceIdentifier, initializer: @MainActor @escaping (Container) -> Wrapped) {
+ public init<InstanceIdentifier: Hashable & Sendable>(instanceIdentifier: InstanceIdentifier, initializer: @MainActor @escaping @Sendable (Container) -> Wrapped) {
  resolver = {
  let someKey = AnyInstanceIdentifier<Wrapped, InstanceIdentifier>(instanceIdentifier)
  return Container.shared.resolveInstance(for: someKey, via: initializer)

Sources/Etcetera/Global/GloballyIdentifiable.swift

@@ -18,7 +18,7 @@
 public protocol GloballyIdentifiable {
 
  /// The type to be used for per-instance identifiers.
- associatedtype InstanceIdentifier: Hashable
+ associatedtype InstanceIdentifier: Hashable & Sendable
 
  /// Produces an instance of `Self` on demand. This method is called from the
  /// shared dependency container when a cached instance of `Self` cannot be

Sources/Etcetera/Networking/Reachability.swift

@@ -14,7 +14,7 @@ extension Notification.Name {
 }
 
 /// A class that reports whether or not the network is currently reachable.
-public class Reachability: NSObject {
+public final class Reachability: NSObject, Sendable {
 
  /// A more accurate alternative to using a Bool
  public enum Status {
@@ -40,33 +40,29 @@ public class Reachability: NSObject {
  return .probablyNotButWhoKnows
  }
 
- private let reachability: SCNetworkReachability?
- private var lock = os_unfair_lock()
- private var _flags: SCNetworkReachabilityFlags?
+ private let reachability: Protected<SCNetworkReachability?>
+ private let _flags = Protected<SCNetworkReachabilityFlags?>()
+
  private var flags: SCNetworkReachabilityFlags? {
  get {
- os_unfair_lock_lock(&lock)
- let value = _flags
- os_unfair_lock_unlock(&lock)
- return value
+ _flags.current
  }
  set {
- os_unfair_lock_lock(&lock)
- _flags = newValue
- os_unfair_lock_unlock(&lock)
+ _flags.current = newValue
  NotificationCenter.default.post(name: .ReachabilityChanged, object: nil)
  }
  }
 
  public init(host: String = "www.google.com") {
- self.reachability = SCNetworkReachabilityCreateWithName(nil, host)
+ let optionalReachability = SCNetworkReachabilityCreateWithName(nil, host)
+ self.reachability = Protected(optionalReachability)
  super.init()
- guard let reachability = reachability else { return }
+ guard let reachability = optionalReachability else { return }
 
  // Populate the current flags asap.
  var flags = SCNetworkReachabilityFlags()
  SCNetworkReachabilityGetFlags(reachability, &flags)
- _flags = flags
+ self.flags = flags
 
  // Then configure the callback.
  let callback: SCNetworkReachabilityCallBack = { (_, flags, infoPtr) in

Sources/Etcetera/UnifiedLogging/OSActivity.swift

@@ -42,7 +42,7 @@ public struct Activity: @unchecked Sendable {
  // MARK: - Nested Types
 
  /// Swift-native type that corresponds to OS_ACTIVITY_FLAGs.
- public struct Options: OptionSet {
+ public struct Options: OptionSet, Sendable {
  public let rawValue: UInt32
 
  public init(rawValue: UInt32) {