Stream of UserDefaults values (#53)

Co-authored-by: Thomas Grapperon <35562418+tgrapperon@users.noreply.github.com>

Sources/UserDefaultsDependency/UserDefaults+Specializations.swift

@@ -103,6 +103,7 @@ extension UserDefaults.Dependency {
     public func set(_ value: URL?, forKey key: String) {
       self._set(value, key)
     }
+
   #else
     /// Returns the URL value associated with the specified key.
     /// - Parameter key: A key in the current user defaults store.
@@ -142,7 +143,7 @@ extension UserDefaults.Dependency {
   /// is no value associated to `key`, or if `R` cannot be built from the associated value.
   public func rawRepresentable<R: RawRepresentable>(forKey key: String) -> R?
   where R.RawValue == String {
-    self.string(forKey: key).flatMap(R.init(rawValue:))
+    self.string(forKey: key).flatMap(R.init)
   }
 
   /// Sets the value of the specified default key to the specified RawRepresentable `R` value.
@@ -160,7 +161,7 @@ extension UserDefaults.Dependency {
   /// is no value associated to `key`, or if `R` cannot be built from the associated value.
   public func rawRepresentable<R: RawRepresentable>(forKey key: String) -> R?
   where R.RawValue == Int {
-    self.integer(forKey: key).flatMap(R.init(rawValue:))
+    self.integer(forKey: key).flatMap(R.init)
   }
 
   /// Sets the value of the specified default key to the specified RawRepresentable `R` value.
@@ -173,6 +174,106 @@ extension UserDefaults.Dependency {
   }
 }
 
+extension UserDefaults.Dependency {
+  /// An `AsyncStream` of Boolean values for a given `key` as they change. The stream produces `nil`
+  /// if no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `Bool?` values, including the initial value.
+  public func boolValues(forKey key: String) -> AsyncStream<Bool?> {
+    self._values(key, Bool.self).map { $0 as! Bool? }.eraseToStream()
+  }
+
+  /// An `AsyncStream` of Data values for a given `key` as they change. The stream produces `nil` if
+  /// no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `Data?` values, including the initial value.
+  public func dataValues(forKey key: String) -> AsyncStream<Data?> {
+    self._values(key, Data.self).map { $0 as! Data? }.eraseToStream()
+  }
+
+  /// An `AsyncStream` of Double values for a given `key` as they change. The stream produces `nil`
+  /// if no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `Double?` values, including the initial value.
+  public func doubleValues(forKey key: String) -> AsyncStream<Double?> {
+    self._values(key, Double.self).map { $0 as! Double? }.eraseToStream()
+  }
+
+  /// An `AsyncStream` of Integer values for a given `key` as they change. The stream produces `nil`
+  /// if no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `Int?` values, including the initial value.
+  public func integerValues(forKey key: String) -> AsyncStream<Int?> {
+    self._values(key, Int.self).map { $0 as! Int? }.eraseToStream()
+  }
+
+  /// An `AsyncStream` of String values for a given `key` as they change. The stream produces `nil`
+  /// if no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `String?` values, including the initial value.
+  public func stringValues(forKey key: String) -> AsyncStream<String?> {
+    self._values(key, String.self).map { $0 as! String? }.eraseToStream()
+  }
+
+  #if os(iOS) || os(macOS) || os(tvOS) || os(watchOS)
+    /// An `AsyncStream` of URL values for a given `key` as they change. The stream produces `nil`
+    /// if no value exists for the given key.
+    /// - Parameter key: A key in the current user defaults store.
+    /// - Returns: An `AsyncStream` of `URL?` values, including the initial value.
+    public func urlValues(forKey key: String) -> AsyncStream<URL?> {
+      self._values(key, URL.self).map { $0 as! URL? }.eraseToStream()
+    }
+  #else
+    /// An `AsyncStream` of URL values for a given `key` as they change. The stream produces `nil`
+    /// if no value exists for the given key.
+    /// - Parameter key: A key in the current user defaults store.
+    /// - Returns: An `AsyncStream` of `URL?` values, including the initial value.
+    @available(
+      *, unavailable, message: "Observing URLs from UserDefaults is not supported on this platform."
+    )
+    public func urlValues(forKey key: String) -> AsyncStream<URL?> {
+      self._values(key, URL.self).map { $0 as! URL? }.eraseToStream()
+    }
+  #endif
+
+  /// An `AsyncStream` of `RawRepresentable<String>` values for a given `key` as they change. The
+  /// stream produces `nil` if no value exists for the given key.
+  /// - Parameters:
+  ///   - valueType: The type of `RawRepresentable` values that is produced. You can use this
+  ///   argument if the type system is unable ot infer it from the context.
+  ///   - key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `RawRepresentable<String>?` values, including the initial
+  /// value.
+  public func rawRepresentableValues<R: RawRepresentable>(
+    _ valueType: R.Type = R.self,
+    forKey key: String
+  )
+    -> AsyncStream<R?> where R.RawValue == String
+  {
+    self._values(key, String.self)
+      .map { ($0 as! String?).flatMap(R.init) }
+      .eraseToStream()
+  }
+
+  /// An `AsyncStream` of `RawRepresentable<Int>` values for a given `key` as they change. The
+  /// stream produces `nil` if no value exists for the given key.
+  /// - Parameters:
+  ///   - valueType: The type of `RawRepresentable` values that is produced. You can use this
+  ///   argument if the type system is unable ot infer it from the context.
+  ///   - key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `RawRepresentable<Int>?` values, including the initial value.
+  public func rawRepresentableValues<R: RawRepresentable>(
+    _ valueType: R.Type = R.self,
+    forKey key: String
+  )
+    -> AsyncStream<R?> where R.RawValue == Int
+  {
+    self._values(key, Int.self)
+      .map { ($0 as! Int?).flatMap(R.init) }
+      .eraseToStream()
+  }
+}
+
 // NS Extensions
 extension UserDefaults.Dependency {
   /// Returns the Date value associated with the specified key.
@@ -191,4 +292,12 @@ extension UserDefaults.Dependency {
   public func set(_ value: Date?, forKey key: String) {
     self._set(value, key)
   }
+
+  /// An `AsyncStream` of Date values for a given `key` as they change. The stream produces `nil` if
+  /// if no value exists for the given key.
+  /// - Parameter key: A key in the current user defaults store.
+  /// - Returns: An `AsyncStream` of `Date?` values, including the initial value.
+  public func dateValues(forKey key: String) -> AsyncStream<Date?> {
+    self._values(key, Date.self).map { $0 as! Date? }.eraseToStream()
+  }
 }

Sources/UserDefaultsDependency/UserDefaultsDependency.swift

@@ -270,25 +270,47 @@ extension UserDefaults.Dependency: TestDependencyKey {
     return UserDefaults.Dependency { key, _ in
       storage.value[key]
     } set: { value, key in
+      var valueDidChange = false
       storage.withValue {
+        valueDidChange = !_isEqual($0[key], value)
         $0[key] = value
       }
-      for continuation in continuations.value[key]?.values ?? [:].values {
-        continuation.yield(value)
+      if valueDidChange {
+        for continuation in continuations.value[key]?.values ?? [:].values {
+          continuation.yield(value)
+        }
       }
     } values: { key, _ in
       let id = UUID()
-      let stream = AsyncStream((any Sendable)?.self) { streamContinuation in
-        continuations.withValue {
-          $0[key, default: [:]][id] = streamContinuation
-        }
+      let (stream, continuation) = AsyncStream.streamWithContinuation(
+        (any Sendable)?.self,
+        bufferingPolicy: .bufferingNewest(1)
+      )
+      continuations.withValue {
+        $0[key, default: [:]][id] = continuation
       }
-      defer { continuations.value[key]?[id]?.yield(storage.value[key]) }
+      continuation.yield(storage.value[key])
       return stream
     }
   }
 }
 
+fileprivate func _isEqual(_ lhs: (any Sendable)?, _ rhs: (any Sendable)?) -> Bool {
+  switch (lhs, rhs) {
+  case let (.some(lhs), .some(rhs)):
+    return (lhs as! any Equatable).isEqual(other: rhs)
+  case (.none, .none):
+    return type(of: lhs) == type(of: rhs)
+  case (.some, .none), (.none, .some): return false
+  }
+}
+
+extension Equatable {
+  fileprivate func isEqual(other: Any) -> Bool {
+    self == other as? Self
+  }
+}
+
 #if os(iOS) || os(macOS) || os(tvOS) || os(watchOS)
 extension UserDefaults.Dependency {
   /// An iCloud-based container of key-value pairs you use to share data among