Apply operations on ACK (RTO20)

Instead of waiting for the server to echo back an operation before
applying it locally, operations are now applied immediately upon
receiving the ACK from Realtime.

Implements the behaviours from spec commit 56a0bba and ports the
corresponding integration tests from ably-js commit 6b1c2de.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lawrence-forooghian

AblyLiveObjects.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -19,12 +19,12 @@ let package = Package(
     ],
     dependencies: [
         .package(
-            url: "https://github.com/ably/ably-cocoa",
-            from: "1.2.55",
+            url: "https://github.com/ably/ably-cocoa.git",
+            revision: "5ce0a5866ce691b9bbdbd62b8c03d3adac356ba6",
         ),
         .package(
-            url: "https://github.com/ably/ably-cocoa-plugin-support",
-            from: "1.0.0",
+            url: "https://github.com/ably/ably-cocoa-plugin-support.git",
+            revision: "242fac1d4a829c8a63f9b3f96a71809e1f6eeffc",
         ),
         .package(
             url: "https://github.com/apple/swift-argument-parser",

Package.resolved

@@ -6,18 +6,21 @@ import Ably
 /// This provides us with a mockable interface to ably-cocoa, and it also allows internal components and their tests not to need to worry about some of the boring details of how we bridge Swift types to `_AblyPluginSupportPrivate`'s Objective-C API (i.e. boxing).
 internal protocol CoreSDK: AnyObject, Sendable {
     /// Implements the internal `#publish` method of RTO15.
-    func nosync_publish(objectMessages: [OutboundObjectMessage], callback: @escaping @Sendable (Result<Void, ARTErrorInfo>) -> Void)
+    func nosync_publish(objectMessages: [OutboundObjectMessage], callback: @escaping @Sendable (Result<PublishResult, ARTErrorInfo>) -> Void)
 
     /// Implements the server time fetch of RTO16, including the storing and usage of the local clock offset.
     func nosync_fetchServerTime(callback: @escaping @Sendable (Result<Date, ARTErrorInfo>) -> Void)
 
     /// Replaces the implementation of ``nosync_publish(objectMessages:callback:)``.
     ///
     /// Used by integration tests, for example to disable `ObjectMessage` publishing so that a test can verify that a behaviour is not a side effect of an `ObjectMessage` sent by the SDK.
-    func testsOnly_overridePublish(with newImplementation: @escaping ([OutboundObjectMessage]) async throws(ARTErrorInfo) -> Void)
+    func testsOnly_overridePublish(with newImplementation: @escaping ([OutboundObjectMessage]) async throws(ARTErrorInfo) -> PublishResult)
 
     /// Returns the current state of the Realtime channel that this wraps.
     var nosync_channelState: _AblyPluginSupportPrivate.RealtimeChannelState { get }
+
+    /// Returns the `siteCode` from the latest `connectionDetails`, or nil if unavailable.
+    func nosync_siteCode() -> String?
 }
 
 internal final class DefaultCoreSDK: CoreSDK {
@@ -34,7 +37,7 @@ internal final class DefaultCoreSDK: CoreSDK {
     /// This enables the `testsOnly_overridePublish(with:)` test hook.
     ///
     /// - Note: This should be `throws(ARTErrorInfo)` but that causes a compilation error of "Runtime support for typed throws function types is only available in macOS 15.0.0 or newer".
-    private nonisolated(unsafe) var overriddenPublishImplementation: (([OutboundObjectMessage]) async throws -> Void)?
+    private nonisolated(unsafe) var overriddenPublishImplementation: (([OutboundObjectMessage]) async throws -> PublishResult)?
 
     internal init(
         channel: _AblyPluginSupportPrivate.RealtimeChannel,
@@ -50,7 +53,7 @@ internal final class DefaultCoreSDK: CoreSDK {
 
     // MARK: - CoreSDK conformance
 
-    internal func nosync_publish(objectMessages: [OutboundObjectMessage], callback: @escaping @Sendable (Result<Void, ARTErrorInfo>) -> Void) {
+    internal func nosync_publish(objectMessages: [OutboundObjectMessage], callback: @escaping @Sendable (Result<PublishResult, ARTErrorInfo>) -> Void) {
         logger.log("nosync_publish(objectMessages: \(LoggingUtilities.formatObjectMessagesForLogging(objectMessages)))", level: .debug)
 
         // Use the overridden implementation if supplied
@@ -61,8 +64,8 @@ internal final class DefaultCoreSDK: CoreSDK {
             let queue = pluginAPI.internalQueue(for: client)
             Task {
                 do {
-                    try await overriddenImplementation(objectMessages)
-                    queue.async { callback(.success(())) }
+                    let publishResult = try await overriddenImplementation(objectMessages)
+                    queue.async { callback(.success((publishResult))) }
                 } catch {
                     guard let artErrorInfo = error as? ARTErrorInfo else {
                         preconditionFailure("Expected ARTErrorInfo, got \(error)")
@@ -83,7 +86,7 @@ internal final class DefaultCoreSDK: CoreSDK {
         )
     }
 
-    internal func testsOnly_overridePublish(with newImplementation: @escaping ([OutboundObjectMessage]) async throws(ARTErrorInfo) -> Void) {
+    internal func testsOnly_overridePublish(with newImplementation: @escaping ([OutboundObjectMessage]) async throws(ARTErrorInfo) -> PublishResult) {
         mutex.withLock {
             overriddenPublishImplementation = newImplementation
         }
@@ -109,6 +112,10 @@ internal final class DefaultCoreSDK: CoreSDK {
     internal var nosync_channelState: _AblyPluginSupportPrivate.RealtimeChannelState {
         pluginAPI.nosync_state(for: channel)
     }
+
+    internal func nosync_siteCode() -> String? {
+        DefaultInternalPlugin.siteCode(client: client, pluginAPI: pluginAPI)
+    }
 }
 
 // MARK: - Channel State Validation

Package.swift

@@ -70,10 +70,10 @@ internal final class DefaultInternalPlugin: NSObject, _AblyPluginSupportPrivate.
     /// A class that wraps an object message.
     ///
     /// We need this intermediate type because we want object messages to be structs — because they're nicer to work with internally — but a struct can't conform to the class-bound `_AblyPluginSupportPrivate.ObjectMessageProtocol`.
-    private final class ObjectMessageBox<T>: _AblyPluginSupportPrivate.ObjectMessageProtocol where T: Sendable {
+    internal final class ObjectMessageBox<T>: _AblyPluginSupportPrivate.ObjectMessageProtocol where T: Sendable {
         internal let objectMessage: T
 
-        init(objectMessage: T) {
+        internal init(objectMessage: T) {
             self.objectMessage = objectMessage
         }
     }
@@ -143,6 +143,11 @@ internal final class DefaultInternalPlugin: NSObject, _AblyPluginSupportPrivate.
         )
     }
 
+    internal func nosync_onChannelStateChanged(_ channel: _AblyPluginSupportPrivate.RealtimeChannel, toState state: _AblyPluginSupportPrivate.RealtimeChannelState, reason: (any _AblyPluginSupportPrivate.PublicErrorInfo)?) {
+        let errorReason = reason.map { ARTErrorInfo.castPluginPublicErrorInfo($0) }
+        nosync_realtimeObjects(for: channel).nosync_onChannelStateChanged(toState: state, reason: errorReason)
+    }
+
     internal func nosync_onConnected(withConnectionDetails connectionDetails: (any ConnectionDetailsProtocol)?, channel: any RealtimeChannel) {
         let gracePeriod = connectionDetails?.objectsGCGracePeriod?.doubleValue ?? InternalDefaultRealtimeObjects.GarbageCollectionOptions.defaultGracePeriod
 
@@ -157,22 +162,53 @@ internal final class DefaultInternalPlugin: NSObject, _AblyPluginSupportPrivate.
         channel: _AblyPluginSupportPrivate.RealtimeChannel,
         client: _AblyPluginSupportPrivate.RealtimeClient,
         pluginAPI: PluginAPIProtocol,
-        callback: @escaping @Sendable (Result<Void, ARTErrorInfo>) -> Void,
+        callback: @escaping @Sendable (Result<PublishResult, ARTErrorInfo>) -> Void,
     ) {
         let objectMessageBoxes: [ObjectMessageBox<OutboundObjectMessage>] = objectMessages.map { .init(objectMessage: $0) }
         let internalQueue = pluginAPI.internalQueue(for: client)
+        
+        let selector = NSSelectorFromString("nosync_sendObjectWithObjectMessages:channel:completionWithResult:")
+        guard (pluginAPI as AnyObject).responds(to: selector) else {
+            fatalError("ably-cocoa does not implement nosync_sendObjectWithObjectMessages:channel:completionWithResult:. Please update ably-cocoa to a version that supports apply-on-ACK.")
+        }
 
-        pluginAPI.nosync_sendObject(
+        pluginAPI.nosync_sendObject!(
             withObjectMessages: objectMessageBoxes,
             channel: channel,
-        ) { error in
+        ) { error, pluginPublishResult in
             dispatchPrecondition(condition: .onQueue(internalQueue))
 
             if let error {
                 callback(.failure(ARTErrorInfo.castPluginPublicErrorInfo(error)))
             } else {
-                callback(.success(()))
+                guard let pluginPublishResult else {
+                    preconditionFailure("Got nil publishResult and nil error")
+                }
+                
+                let publishResult = PublishResult(pluginPublishResult: pluginPublishResult)
+                callback(.success((publishResult)))
             }
         }
     }
+
+    // MARK: - Connection Details
+
+    /// Returns the `siteCode` from the latest `connectionDetails`, or nil if unavailable.
+    internal static func siteCode(
+        client: _AblyPluginSupportPrivate.RealtimeClient,
+        pluginAPI: PluginAPIProtocol,
+    ) -> String? {
+        guard let connectionDetails = pluginAPI.nosync_latestConnectionDetails(for: client) else {
+            return nil
+        }
+
+        // siteCode is @optional on the protocol; use responds(to:) to distinguish
+        // "not implemented" from "returns nil"
+        let selector = NSSelectorFromString("siteCode")
+        guard (connectionDetails as AnyObject).responds(to: selector) else {
+            fatalError("ably-cocoa's connectionDetails does not implement siteCode. Please update ably-cocoa to a version that supports apply-on-ACK.")
+        }
+
+        return connectionDetails.siteCode?()
+    }
 }

Sources/AblyLiveObjects/Internal/CoreSDK.swift

@@ -103,7 +103,7 @@ internal final class InternalDefaultLiveCounter: Sendable {
         }
     }
 
-    internal func increment(amount: Double, coreSDK: CoreSDK) async throws(ARTErrorInfo) {
+    internal func increment(amount: Double, coreSDK: CoreSDK, realtimeObjects: InternalDefaultRealtimeObjects) async throws(ARTErrorInfo) {
         try await withCheckedContinuation { (continuation: CheckedContinuation<Result<Void, ARTErrorInfo>, _>) in
             do throws(ARTErrorInfo) {
                 try mutableStateMutex.withSync { mutableState throws(ARTErrorInfo) in
@@ -131,8 +131,8 @@ internal final class InternalDefaultLiveCounter: Sendable {
                         ),
                     )
 
-                    // RTLC12f
-                    coreSDK.nosync_publish(objectMessages: [objectMessage]) { result in
+                    // RTLC12g
+                    realtimeObjects.nosync_publishAndApply(objectMessages: [objectMessage]) { result in
                         continuation.resume(returning: result)
                     }
                 }
@@ -142,9 +142,9 @@ internal final class InternalDefaultLiveCounter: Sendable {
         }.get()
     }
 
-    internal func decrement(amount: Double, coreSDK: CoreSDK) async throws(ARTErrorInfo) {
+    internal func decrement(amount: Double, coreSDK: CoreSDK, realtimeObjects: InternalDefaultRealtimeObjects) async throws(ARTErrorInfo) {
         // RTLC13b
-        try await increment(amount: -amount, coreSDK: coreSDK)
+        try await increment(amount: -amount, coreSDK: coreSDK, realtimeObjects: realtimeObjects)
     }
 
     @discardableResult
@@ -245,13 +245,17 @@ internal final class InternalDefaultLiveCounter: Sendable {
     }
 
     /// Attempts to apply an operation from an inbound `ObjectMessage`, per RTLC7.
+    ///
+    /// - Returns: `true` if the operation was applied, `false` if it was skipped (RTLC7g).
+    @discardableResult
     internal func nosync_apply(
         _ operation: ObjectOperation,
         objectMessageSerial: String?,
         objectMessageSiteCode: String?,
         objectMessageSerialTimestamp: Date?,
         objectsPool: inout ObjectsPool,
-    ) {
+        source: ObjectsOperationSource,
+    ) -> Bool {
         mutableStateMutex.withoutSync { mutableState in
             mutableState.apply(
                 operation,
@@ -262,6 +266,7 @@ internal final class InternalDefaultLiveCounter: Sendable {
                 logger: logger,
                 clock: clock,
                 userCallbackQueue: userCallbackQueue,
+                source: source,
             )
         }
     }
@@ -379,6 +384,8 @@ internal final class InternalDefaultLiveCounter: Sendable {
         }
 
         /// Attempts to apply an operation from an inbound `ObjectMessage`, per RTLC7.
+        ///
+        /// - Returns: `true` if the operation was applied, `false` if skipped (RTLC7g).
         internal mutating func apply(
             _ operation: ObjectOperation,
             objectMessageSerial: String?,
@@ -388,20 +395,22 @@ internal final class InternalDefaultLiveCounter: Sendable {
             logger: Logger,
             clock: SimpleClock,
             userCallbackQueue: DispatchQueue,
-        ) {
+            source: ObjectsOperationSource,
+        ) -> Bool {
             guard let applicableOperation = liveObjectMutableState.canApplyOperation(objectMessageSerial: objectMessageSerial, objectMessageSiteCode: objectMessageSiteCode, logger: logger) else {
                 // RTLC7b
                 logger.log("Operation \(operation) (serial: \(String(describing: objectMessageSerial)), siteCode: \(String(describing: objectMessageSiteCode))) should not be applied; discarding", level: .debug)
-                return
+                return false
             }
 
-            // RTLC7c
-            liveObjectMutableState.siteTimeserials[applicableOperation.objectMessageSiteCode] = applicableOperation.objectMessageSerial
+            // RTLC7c: Only update siteTimeserials for channel-sourced operations
+            if source == .channel {
+                liveObjectMutableState.siteTimeserials[applicableOperation.objectMessageSiteCode] = applicableOperation.objectMessageSerial
+            }
 
             // RTLC7e
-            // TODO: are we still meant to update siteTimeserials? https://github.com/ably/specification/pull/350/files#r2218718854
             if liveObjectMutableState.isTombstone {
-                return
+                return false
             }
 
             switch operation.action {
@@ -413,11 +422,15 @@ internal final class InternalDefaultLiveCounter: Sendable {
                 )
                 // RTLC7d1a
                 liveObjectMutableState.emit(update, on: userCallbackQueue)
+                // RTLC7d1b
+                return true
             case .known(.counterInc):
                 // RTLC7d2
                 let update = applyCounterIncOperation(operation.counterOp)
                 // RTLC7d2a
                 liveObjectMutableState.emit(update, on: userCallbackQueue)
+                // RTLC7d2b
+                return true
             case .known(.objectDelete):
                 let dataBeforeApplyingOperation = data
 
@@ -431,9 +444,12 @@ internal final class InternalDefaultLiveCounter: Sendable {
 
                 // RTLC7d4a
                 liveObjectMutableState.emit(.update(.init(amount: -dataBeforeApplyingOperation)), on: userCallbackQueue)
+                // RTLC7d4b
+                return true
             default:
                 // RTLC7d3
                 logger.log("Operation \(operation) has unsupported action for LiveCounter; discarding", level: .warn)
+                return false
             }
         }