[ECO-5149] Implement lifecycle contributor precedence

Sources/AblyChat/Room.swift

@@ -96,7 +96,6 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
             }
         }
 
-        /// The features are returned in CHA-RC2e order.
         static func fromRoomOptions(_ roomOptions: RoomOptions) -> [Self] {
             var result: [Self] = [.messages]
 
@@ -204,8 +203,6 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
     }
 
     /// Each feature in `featuresWithOptions` is guaranteed to appear in the `features` member of precisely one of the returned array’s values.
-    ///
-    /// The elements of `featuresWithOptions` must be in CHA-RC2e order.
     private static func createFeatureChannelPartialDependencies(roomID: String, featuresWithOptions: [RoomFeatureWithOptions], realtime: RealtimeClient) -> [(features: [RoomFeature], featureChannelPartialDependencies: FeatureChannelPartialDependencies)] {
         // CHA-RC3a
 
@@ -215,7 +212,7 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
 
         let featuresGroupedByChannelName = Dictionary(grouping: featuresWithOptions) { $0.toRoomFeature.channelNameForRoomID(roomID) }
 
-        return featuresGroupedByChannelName.map { channelName, features in
+        let unorderedResult = featuresGroupedByChannelName.map { channelName, features in
             var channelOptions = RealtimeChannelOptions()
 
             // channel setup for presence and occupancy
@@ -241,13 +238,16 @@ internal actor DefaultRoom<LifecycleManagerFactory: RoomLifecycleManagerFactory>
             let channel = realtime.getChannel(channelName, opts: channelOptions)
 
             // Give the contributor the first of the enabled features that correspond to this channel, using CHA-RC2e ordering. This will determine which feature is used for atttachment and detachment errors.
-            let contributorFeature = features[0].toRoomFeature
+            let contributorFeature = features.map(\.toRoomFeature).sorted { RoomFeature.areInPrecedenceListOrder($0, $1) }[0]
 
             let contributor = DefaultRoomLifecycleContributor(channel: .init(underlyingChannel: channel), feature: contributorFeature)
             let featureChannelPartialDependencies = FeatureChannelPartialDependencies(channel: channel, contributor: contributor)
 
             return (features.map(\.toRoomFeature), featureChannelPartialDependencies)
         }
+
+        // Sort the result in CHA-RC2e order
+        return unorderedResult.sorted { RoomFeature.areInPrecedenceListOrder($0.1.contributor.feature, $1.1.contributor.feature) }
     }
 
     private static func createFeatureChannels(partialDependencies: [(features: [RoomFeature], featureChannelPartialDependencies: FeatureChannelPartialDependencies)], lifecycleManager: RoomLifecycleManager) -> [RoomFeature: DefaultFeatureChannel] {

Sources/AblyChat/RoomFeature.swift

@@ -1,12 +1,13 @@
 import Ably
 
 /// The features offered by a chat room.
-internal enum RoomFeature {
+internal enum RoomFeature: CaseIterable {
+    // This list MUST be kept in the same order as the list in CHA-RC2e, in order for the implementation of `areInPrecedenceListOrder` to work.
     case messages
     case presence
+    case typing
     case reactions
     case occupancy
-    case typing
 
     internal func channelNameForRoomID(_ roomID: String) -> String {
         "\(roomID)::$chat::$\(channelNameSuffix)"
@@ -27,6 +28,14 @@ internal enum RoomFeature {
             "typingIndicators"
         }
     }
+
+    /// Returns a `Bool` indicating whether `first` and `second` are in the same order as the list given in CHA-RC2e.
+    internal static func areInPrecedenceListOrder(_ first: Self, _ second: Self) -> Bool {
+        let allCases = Self.allCases
+        let indexOfFirst = allCases.firstIndex(of: first)!
+        let indexOfSecond = allCases.firstIndex(of: second)!
+        return indexOfFirst < indexOfSecond
+    }
 }
 
 /// Provides all of the channel-related functionality that a room feature (e.g. an implementation of ``Messages``) needs.

Tests/AblyChatTests/DefaultRoomTests.swift

@@ -100,6 +100,30 @@ struct DefaultRoomTests {
         #expect(Set(channelsGetArguments.map(\.name)) == Set(expectedFetchedChannelNames))
     }
 
+    // @spec CHA-RC2e
+    // @spec CHA-RL10
+    @Test
+    func lifecycleContributorOrder() async throws {
+        // Given: a DefaultRoom, instance, with all room features enabled
+        let channelsList = [
+            MockRealtimeChannel(name: "basketball::$chat::$chatMessages"),
+            MockRealtimeChannel(name: "basketball::$chat::$reactions"),
+            MockRealtimeChannel(name: "basketball::$chat::$typingIndicators"),
+        ]
+        let channels = MockChannels(channels: channelsList)
+        let realtime = MockRealtime.create(channels: channels)
+        let lifecycleManagerFactory = MockRoomLifecycleManagerFactory()
+        _ = try await DefaultRoom(realtime: realtime, chatAPI: ChatAPI(realtime: realtime), roomID: "basketball", options: .allFeaturesEnabled, logger: TestLogger(), lifecycleManagerFactory: lifecycleManagerFactory)
+
+        // Then: The array of contributors with which it initializes the RoomLifecycleManager are in the same order as the following list:
+        //
+        // messages, presence, typing, reactions, occupancy
+        //
+        // (note that we do not say that it is the _same_ list, because we combine multiple features into a single contributor)
+        let lifecycleManagerCreationArguments = try #require(await lifecycleManagerFactory.createManagerArguments.first)
+        #expect(lifecycleManagerCreationArguments.contributors.map(\.feature) == [.messages, .typing, .reactions])
+    }
+
     // @specUntested CHA-RC2b - We chose to implement this failure with an idiomatic fatalError instead of throwing, but we can’t test this.
 
     // This is just a basic sense check to make sure the room getters are working as expected, since we don’t have unit tests for some of the features at the moment.