refactor ObservationToken

Package.swift

@@ -66,7 +66,12 @@ let package = Package(
       ],
       resources: [.process("Resources")]
     ),
-    .target(name: "Functions", dependencies: ["Helpers"]),
+    .target(
+      name: "Functions",
+      dependencies: [
+        "Helpers",
+      ]
+    ),
     .testTarget(
       name: "FunctionsTests",
       dependencies: [

Sources/Functions/FunctionsClient.swift

@@ -21,19 +21,36 @@ public final class FunctionsClient: Sendable {
   /// The Region to invoke the functions in.
   let region: String?
 
-  private let http: any HTTPClientType
-
   struct MutableState {
     /// Headers to be included in the requests.
     var headers = HTTPHeaders()
   }
 
+  private let http: any HTTPClientType
   private let mutableState = LockIsolated(MutableState())
 
   var headers: HTTPHeaders {
     mutableState.headers
   }
 
+  init(
+    url: URL,
+    headers: [String: String],
+    region: String?,
+    http: any HTTPClientType
+  ) {
+    self.url = url
+    self.region = region
+    self.http = http
+
+    mutableState.withValue {
+      $0.headers = HTTPHeaders(headers)
+      if $0.headers["X-Client-Info"] == nil {
+        $0.headers["X-Client-Info"] = "functions-swift/\(version)"
+      }
+    }
+  }
+
   /// Initializes a new instance of `FunctionsClient`.
   ///
   /// - Parameters:
@@ -60,24 +77,6 @@ public final class FunctionsClient: Sendable {
     self.init(url: url, headers: headers, region: region, http: http)
   }
 
-  init(
-    url: URL,
-    headers: [String: String],
-    region: String?,
-    http: any HTTPClientType
-  ) {
-    self.url = url
-    self.region = region
-    self.http = http
-
-    mutableState.withValue {
-      $0.headers = HTTPHeaders(headers)
-      if $0.headers["X-Client-Info"] == nil {
-        $0.headers["X-Client-Info"] = "functions-swift/\(version)"
-      }
-    }
-  }
-
   /// Initializes a new instance of `FunctionsClient`.
   ///
   /// - Parameters:

Sources/Helpers/EventEmitter.swift

@@ -8,11 +8,16 @@
 import ConcurrencyExtras
 import Foundation
 
-public final class ObservationToken: Sendable, Hashable {
-  let _onCancel = LockIsolated((@Sendable () -> Void)?.none)
+public final class ObservationToken: @unchecked Sendable, Hashable {
+  private let _isCancelled = LockIsolated(false)
+  package var onCancel: @Sendable () -> Void
 
-  package init(_ onCancel: (@Sendable () -> Void)? = nil) {
-    _onCancel.setValue(onCancel)
+  public var isCancelled: Bool {
+    _isCancelled.withValue { $0 }
+  }
+
+  package init(onCancel: @escaping @Sendable () -> Void = {}) {
+    self.onCancel = onCancel
   }
 
   @available(*, deprecated, renamed: "cancel")
@@ -21,13 +26,10 @@ public final class ObservationToken: Sendable, Hashable {
   }
 
   public func cancel() {
-    _onCancel.withValue {
-      if $0 == nil {
-        return
-      }
-
-      $0?()
-      $0 = nil
+    _isCancelled.withValue { isCancelled in
+      guard !isCancelled else { return }
+      defer { isCancelled = true }
+      onCancel()
     }
   }
 
@@ -36,7 +38,7 @@ public final class ObservationToken: Sendable, Hashable {
   }
 
   public static func == (lhs: ObservationToken, rhs: ObservationToken) -> Bool {
-    ObjectIdentifier(lhs) == ObjectIdentifier(rhs)
+    lhs === rhs
   }
 
   public func hash(into hasher: inout Hasher) {
@@ -45,6 +47,10 @@ public final class ObservationToken: Sendable, Hashable {
 }
 
 extension ObservationToken {
+  public func store(in collection: inout some RangeReplaceableCollection<ObservationToken>) {
+    collection.append(self)
+  }
+
   public func store(in set: inout Set<ObservationToken>) {
     set.insert(self)
   }
@@ -53,7 +59,7 @@ extension ObservationToken {
 package final class EventEmitter<Event: Sendable>: Sendable {
   public typealias Listener = @Sendable (Event) -> Void
 
-  private let listeners = LockIsolated<[ObjectIdentifier: Listener]>([:])
+  private let listeners = LockIsolated<[(key: ObjectIdentifier, listener: Listener)]>([])
   private let _lastEvent: LockIsolated<Event>
   package var lastEvent: Event { _lastEvent.value }
 
@@ -77,14 +83,14 @@ package final class EventEmitter<Event: Sendable>: Sendable {
     let token = ObservationToken()
     let key = ObjectIdentifier(token)
 
-    token._onCancel.setValue { [weak self] in
+    token.onCancel = { [weak self] in
       self?.listeners.withValue {
-        $0[key] = nil
+        $0.removeAll { $0.key == key }
       }
     }
 
     listeners.withValue {
-      $0[key] = listener
+      $0.append((key, listener))
     }
 
     return token
@@ -95,9 +101,9 @@ package final class EventEmitter<Event: Sendable>: Sendable {
     let listeners = listeners.value
 
     if let token {
-      listeners[ObjectIdentifier(token)]?(event)
+      listeners.first { $0.key == ObjectIdentifier(token) }?.listener(event)
     } else {
-      for listener in listeners.values {
+      for (_, listener) in listeners {
         listener(event)
       }
     }