Swift 6: Room and Track state (#652)

This is the last 🎉 portion of Swift 6 warnings, mostly around `State`.

The algorithm is still pretty simple:
- can be `final (internal)`/immutable → make it `Sendable`
- is already public/inherited → make it `@unchecked Sendable`

Unit tests are mostly `@unchecked` because of inheritance, IMO gradually
moving to Swift Testing is more important.

Fortunately, for most generic/async stuff `T: Sendable` is just works
(tm), just needs proper annotations.

Author: pblazej

.nanpa/swift-6-state.kdl

@@ -0,0 +1 @@
+patch type="fixed" "Swift 6: Fixed warnings for mutable state"

Sources/LiveKit/Broadcast/BroadcastBundleInfo.swift

@@ -18,7 +18,7 @@
 
 import Foundation
 
-enum BroadcastBundleInfo {
+actor BroadcastBundleInfo {
     /// Identifier of the app group shared by the primary app and broadcast extension.
     static var groupIdentifier: String? {
         if let override = groupIdentifierOverride { return override }

Sources/LiveKit/Broadcast/BroadcastScreenCapturer.swift

@@ -28,7 +28,7 @@ internal import LiveKitWebRTC
 @_implementationOnly import LiveKitWebRTC
 #endif
 
-class BroadcastScreenCapturer: BufferCapturer {
+class BroadcastScreenCapturer: BufferCapturer, @unchecked Sendable {
     private let appAudio: Bool
     private var receiver: BroadcastReceiver?
 

Sources/LiveKit/Broadcast/IPC/BroadcastImageCodec.swift

@@ -17,10 +17,10 @@
 #if os(iOS)
 
 import AVFoundation
-import CoreImage
+@preconcurrency import CoreImage
 
 /// Encode and decode image samples for transport.
-struct BroadcastImageCodec {
+struct BroadcastImageCodec: Sendable {
     struct Metadata: Codable {
         let width: Int
         let height: Int

Sources/LiveKit/Broadcast/LKSampleHandler.swift

@@ -34,7 +34,7 @@ import LKObjCHelpers
 #endif
 
 @available(macCatalyst 13.1, *)
-open class LKSampleHandler: RPBroadcastSampleHandler {
+open class LKSampleHandler: RPBroadcastSampleHandler, @unchecked Sendable {
     private var uploader: BroadcastUploader?
     private var cancellable = Set<AnyCancellable>()
 

Sources/LiveKit/Core/DataChannelPair.swift

@@ -29,7 +29,7 @@ protocol DataChannelDelegate: Sendable {
     func dataChannel(_ dataChannelPair: DataChannelPair, didReceiveDataPacket dataPacket: Livekit_DataPacket)
 }
 
-class DataChannelPair: NSObject, Loggable {
+class DataChannelPair: NSObject, @unchecked Sendable, Loggable {
     // MARK: - Public
 
     public let delegates = MulticastDelegate<DataChannelDelegate>(label: "DataChannelDelegate")
@@ -48,6 +48,8 @@ class DataChannelPair: NSObject, Loggable {
             guard let lossy, let reliable else { return false }
             return reliable.readyState == .open && lossy.readyState == .open
         }
+
+        var eventContinuation: AsyncStream<ChannelEvent>.Continuation?
     }
 
     private let _state: StateSync<State>
@@ -61,24 +63,22 @@ class DataChannelPair: NSObject, Loggable {
         var amount: UInt64 = 0
     }
 
-    private struct PublishDataRequest {
+    private struct PublishDataRequest: Sendable {
         let data: LKRTCDataBuffer
         let continuation: CheckedContinuation<Void, any Error>?
     }
 
-    private struct ChannelEvent {
+    private struct ChannelEvent: Sendable {
         let channelKind: ChannelKind
         let detail: Detail
 
-        enum Detail {
+        enum Detail: Sendable {
             case publishData(PublishDataRequest)
             case bufferedAmountChanged(UInt64)
         }
     }
 
-    private var eventContinuation: AsyncStream<ChannelEvent>.Continuation?
-
-    @Sendable private func handleEvents(
+    private func handleEvents(
         events: AsyncStream<ChannelEvent>
     ) async {
         var lossyBuffering = BufferingState()
@@ -175,7 +175,7 @@ class DataChannelPair: NSObject, Loggable {
 
         Task {
             let eventStream = AsyncStream<ChannelEvent> { continuation in
-                self.eventContinuation = continuation
+                _state.mutate { $0.eventContinuation = continuation }
             }
             await handleEvents(events: eventStream)
         }
@@ -241,7 +241,7 @@ class DataChannelPair: NSObject, Loggable {
                 channelKind: ChannelKind(packet.kind), // TODO: field is deprecated
                 detail: .publishData(request)
             )
-            eventContinuation?.yield(event)
+            _state.eventContinuation?.yield(event)
         }
     }
 
@@ -255,7 +255,7 @@ class DataChannelPair: NSObject, Loggable {
     private static let lossyLowThreshold: UInt64 = reliableLowThreshold
 
     deinit {
-        eventContinuation?.finish()
+        _state.eventContinuation?.finish()
     }
 }
 
@@ -267,7 +267,7 @@ extension DataChannelPair: LKRTCDataChannelDelegate {
             channelKind: dataChannel.kind,
             detail: .bufferedAmountChanged(amount)
         )
-        eventContinuation?.yield(event)
+        _state.eventContinuation?.yield(event)
     }
 
     func dataChannelDidChangeState(_: LKRTCDataChannel) {

Sources/LiveKit/Core/RPC.swift

@@ -120,7 +120,7 @@ let MAX_RPC_PAYLOAD_BYTES = 15360 // 15 KB
 /// Throwing an `RpcError` will send the error back to the requester.
 ///
 /// - SeeAlso: `LocalParticipant.registerRpcMethod`
-public typealias RpcHandler = (RpcInvocationData) async throws -> String
+public typealias RpcHandler = @Sendable (RpcInvocationData) async throws -> String
 
 public struct RpcInvocationData {
     /// A unique identifier for this RPC request
@@ -136,9 +136,9 @@ public struct RpcInvocationData {
     public let responseTimeout: TimeInterval
 }
 
-struct PendingRpcResponse {
+struct PendingRpcResponse: Sendable {
     let participantIdentity: Participant.Identity
-    let onResolve: (_ payload: String?, _ error: RpcError?) -> Void
+    let onResolve: @Sendable (_ payload: String?, _ error: RpcError?) -> Void
 }
 
 actor RpcStateManager: Loggable {

Sources/LiveKit/Core/Room+Engine.swift

@@ -30,7 +30,7 @@ internal import LiveKitWebRTC
 extension Room {
     // MARK: - Public
 
-    typealias ConditionEvalFunc = (_ newState: State, _ oldState: State?) -> Bool
+    typealias ConditionEvalFunc = @Sendable (_ newState: State, _ oldState: State?) -> Bool
 
     // MARK: - Private
 
@@ -207,7 +207,7 @@ extension Room {
 extension Room {
     func execute(when condition: @escaping ConditionEvalFunc,
                  removeWhen removeCondition: @escaping ConditionEvalFunc,
-                 _ block: @escaping () -> Void)
+                 _ block: @Sendable @escaping () -> Void)
     {
         // already matches condition, execute immediately
         if _state.read({ condition($0, nil) }) {

Sources/LiveKit/Core/Room+EngineDelegate.swift

@@ -96,7 +96,7 @@ extension Room {
         }
 
         // Notify change when engine's state mutates
-        Task.detached { @MainActor in
+        Task { @MainActor in
             self.objectWillChange.send()
         }
     }

Sources/LiveKit/Core/Room.swift

@@ -21,7 +21,7 @@ import Network
 #endif
 
 @objc
-public class Room: NSObject, ObservableObject, Loggable {
+public class Room: NSObject, @unchecked Sendable, ObservableObject, Loggable {
     // MARK: - MulticastDelegate
 
     public let delegates = MulticastDelegate<RoomDelegate>(label: "RoomDelegate")
@@ -133,7 +133,7 @@ public class Room: NSObject, ObservableObject, Loggable {
 
     // MARK: - State
 
-    struct State: Equatable {
+    struct State: Equatable, Sendable {
         // Options
         var connectOptions: ConnectOptions
         var roomOptions: RoomOptions
@@ -228,7 +228,9 @@ public class Room: NSObject, ObservableObject, Loggable {
         }
 
         // listen to app states
-        AppStateListener.shared.delegates.add(delegate: self)
+        Task { @MainActor in
+            AppStateListener.shared.delegates.add(delegate: self)
+        }
 
         // trigger events when state mutates
         _state.onDidMutate = { [weak self] newState, oldState in
@@ -290,7 +292,7 @@ public class Room: NSObject, ObservableObject, Loggable {
             }
 
             // Notify Room when state mutates
-            Task.detached { @MainActor in
+            Task { @MainActor in
                 self.objectWillChange.send()
             }
         }