Implement Subscription

.github/workflows/check.yaml

@@ -43,7 +43,7 @@ jobs:
         run: swift run BuildTool generate-matrices >> $GITHUB_OUTPUT
 
   check-spm:
-    name: SPM (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})
+    name: SPM (Xcode ${{ matrix.tooling.xcodeVersion }})
     runs-on: macos-latest
     needs: generate-matrices
     strategy:
@@ -57,11 +57,11 @@ jobs:
           xcode-version: ${{ matrix.tooling.xcodeVersion }}
 
       # https://forums.swift.org/t/warnings-as-errors-for-libraries-frameworks/58393/2
-      - run: swift build -Xswiftc -warnings-as-errors -Xswiftc -swift-version -Xswiftc ${{ matrix.tooling.swiftVersion }}
-      - run: swift test -Xswiftc -warnings-as-errors -Xswiftc -swift-version -Xswiftc ${{ matrix.tooling.swiftVersion }}
+      - run: swift build -Xswiftc -warnings-as-errors
+      - run: swift test -Xswiftc -warnings-as-errors
 
   check-xcode:
-    name: Xcode, ${{matrix.platform}} (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})
+    name: Xcode, ${{matrix.platform}} (Xcode ${{ matrix.tooling.xcodeVersion }})
     runs-on: macos-latest
     needs: generate-matrices
 
@@ -76,7 +76,7 @@ jobs:
           xcode-version: ${{ matrix.tooling.xcodeVersion }}
 
       - name: Build and run tests
-        run: swift run BuildTool build-and-test-library --platform ${{ matrix.platform }} --swift-version ${{ matrix.tooling.swiftVersion }}
+        run: swift run BuildTool build-and-test-library --platform ${{ matrix.platform }}
 
   check-example-app:
     name: Example app, ${{matrix.platform}} (Xcode ${{ matrix.tooling.xcodeVersion }}, Swift ${{ matrix.tooling.swiftVersion }})

AblyChat.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -1,5 +1,5 @@
 {
-  "originHash" : "f6b591fa76437494c2609ca1208b8583cbc3debe5e659be06bdcb7bc4bb5e457",
+  "originHash" : "fcc346d6fe86e610ac200cdbbf91c56204df67286546d5079bd9c610ee65953b",
   "pins" : [
     {
       "identity" : "ably-cocoa",
@@ -36,6 +36,24 @@
         "revision" : "41982a3656a71c768319979febd796c6fd111d5c",
         "version" : "1.5.0"
       }
+    },
+    {
+      "identity" : "swift-async-algorithms",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-async-algorithms",
+      "state" : {
+        "revision" : "6ae9a051f76b81cc668305ceed5b0e0a7fd93d20",
+        "version" : "1.0.1"
+      }
+    },
+    {
+      "identity" : "swift-collections",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-collections.git",
+      "state" : {
+        "revision" : "3d2dc41a01f9e49d84f0a3925fb858bed64f702d",
+        "version" : "1.1.2"
+      }
     }
   ],
   "version" : 3

CONTRIBUTING.md

@@ -39,6 +39,9 @@ And, actually more importantly, we want to be sure that the SDK can be integrate
 
 ### Multiple `Package.swift` files
 
-We have a separate manifest file, `Package@swift-6.swift`, which a Swift compiler supporting Swift 6 will use instead of `Package.swift` (see [documentation of this SPM feature](https://github.com/swiftlang/swift-package-manager/blob/74f06f8a7fd6b4c729e474dee34db66319d90759/Documentation/Usage.md#version-specific-manifest-selection)). This file only exists because if you try to use `.enableUpcomingFeature` for a feature that is enabled by default in Swift 6, you’ll get an error `error: upcoming feature 'BareSlashRegexLiterals' is already enabled as of Swift version 6`. (I don’t know if there’s a better way of handling this.)
+We have a separate manifest file, `Package@swift-6.swift`, which a Swift compiler supporting Swift 6 will use instead of `Package.swift` (see [documentation of this SPM feature](https://github.com/swiftlang/swift-package-manager/blob/74f06f8a7fd6b4c729e474dee34db66319d90759/Documentation/Usage.md#version-specific-manifest-selection)). This file exists for two reasons:
+
+1. To tell the compiler “use the Swift 6 language mode to compile this package if the compiler supports Swift 6, else use the Swift 5 language mode” (I previously tried passing `-Xswiftc -swift-version -Xswiftc 6` to `swift build` but this seems to then use Swift 6 language mode for compiling not just our own package, but all of our dependencies, which is likely to fail.)
+2. If you try to use `.enableUpcomingFeature` for a feature that is enabled by default in Swift 6, you’ll get an error `error: upcoming feature 'BareSlashRegexLiterals' is already enabled as of Swift version 6`. (I don’t know if there’s a better way of handling this.)
 
 So, we need to make sure we keep `Package.swift` and `Package@swift-6.swift` in sync manually.

Example/AblyChatExample.xcodeproj/project.pbxproj

@@ -17,6 +17,7 @@
 
 /* Begin PBXFileReference section */
 		212F95A62C6CAD9300420287 /* MockRealtime.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MockRealtime.swift; sourceTree = "<group>"; };
+		214AA9262C778FB70068FD0A /* Config.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = Config.xcconfig; sourceTree = "<group>"; };
 		21F09A9C2C60CAF00025AF73 /* AblyChatExample.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = AblyChatExample.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		21F09A9F2C60CAF00025AF73 /* AblyChatExampleApp.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AblyChatExampleApp.swift; sourceTree = "<group>"; };
 		21F09AA12C60CAF00025AF73 /* ContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContentView.swift; sourceTree = "<group>"; };
@@ -75,6 +76,7 @@
 				212F95A52C6CAD7E00420287 /* Mocks */,
 				21F09A9F2C60CAF00025AF73 /* AblyChatExampleApp.swift */,
 				21F09AA12C60CAF00025AF73 /* ContentView.swift */,
+				214AA9262C778FB70068FD0A /* Config.xcconfig */,
 				21F09AA32C60CAF20025AF73 /* Assets.xcassets */,
 				21F09AA52C60CAF20025AF73 /* AblyChatExample.entitlements */,
 				21F09AA62C60CAF20025AF73 /* Preview Content */,
@@ -174,6 +176,7 @@
 /* Begin XCBuildConfiguration section */
 		21F09AA92C60CAF20025AF73 /* Debug */ = {
 			isa = XCBuildConfiguration;
+			baseConfigurationReference = 214AA9262C778FB70068FD0A /* Config.xcconfig */;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
@@ -238,6 +241,7 @@
 		};
 		21F09AAA2C60CAF20025AF73 /* Release */ = {
 			isa = XCBuildConfiguration;
+			baseConfigurationReference = 214AA9262C778FB70068FD0A /* Config.xcconfig */;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
 				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
@@ -326,7 +330,6 @@
 				SUPPORTED_PLATFORMS = "appletvos appletvsimulator iphoneos iphonesimulator macosx";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
-				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2,3";
 				TVOS_DEPLOYMENT_TARGET = 17.0;
 			};
@@ -366,7 +369,6 @@
 				SUPPORTED_PLATFORMS = "appletvos appletvsimulator iphoneos iphonesimulator macosx";
 				SUPPORTS_MACCATALYST = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
-				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2,3";
 				TVOS_DEPLOYMENT_TARGET = 17.0;
 			};

Example/AblyChatExample/Config.xcconfig

@@ -0,0 +1,3 @@
+// This allows us to specify the Swift version on the command line without affecting the Swift version used for our dependencies (which it appears that specifying SWIFT_VERSION on the command line does).
+EXAMPLE_APP_SWIFT_VERSION = 5.0
+SWIFT_VERSION = $(EXAMPLE_APP_SWIFT_VERSION)

Package.resolved

@@ -1,5 +1,5 @@
 {
-  "originHash" : "f6b591fa76437494c2609ca1208b8583cbc3debe5e659be06bdcb7bc4bb5e457",
+  "originHash" : "fcc346d6fe86e610ac200cdbbf91c56204df67286546d5079bd9c610ee65953b",
   "pins" : [
     {
       "identity" : "ably-cocoa",
@@ -36,6 +36,24 @@
         "revision" : "41982a3656a71c768319979febd796c6fd111d5c",
         "version" : "1.5.0"
       }
+    },
+    {
+      "identity" : "swift-async-algorithms",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-async-algorithms",
+      "state" : {
+        "revision" : "6ae9a051f76b81cc668305ceed5b0e0a7fd93d20",
+        "version" : "1.0.1"
+      }
+    },
+    {
+      "identity" : "swift-collections",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-collections.git",
+      "state" : {
+        "revision" : "3d2dc41a01f9e49d84f0a3925fb858bed64f702d",
+        "version" : "1.1.2"
+      }
     }
   ],
   "version" : 3

Package.swift

@@ -26,6 +26,10 @@ let package = Package(
             url: "https://github.com/apple/swift-argument-parser",
             from: "1.5.0"
         ),
+        .package(
+            url: "https://github.com/apple/swift-async-algorithms",
+            from: "1.0.1"
+        ),
     ],
     targets: [
         .target(
@@ -55,6 +59,10 @@ let package = Package(
             name: "AblyChatTests",
             dependencies: [
                 "AblyChat",
+                .product(
+                    name: "AsyncAlgorithms",
+                    package: "swift-async-algorithms"
+                ),
             ]
         ),
         .executableTarget(
@@ -64,6 +72,10 @@ let package = Package(
                     name: "ArgumentParser",
                     package: "swift-argument-parser"
                 ),
+                .product(
+                    name: "AsyncAlgorithms",
+                    package: "swift-async-algorithms"
+                ),
             ],
             swiftSettings: [
                 // See justification above.

Package@swift-6.swift

@@ -26,6 +26,10 @@ let package = Package(
             url: "https://github.com/apple/swift-argument-parser",
             from: "1.5.0"
         ),
+        .package(
+            url: "https://github.com/apple/swift-async-algorithms",
+            from: "1.0.1"
+        ),
     ],
     targets: [
         .target(
@@ -41,6 +45,10 @@ let package = Package(
             name: "AblyChatTests",
             dependencies: [
                 "AblyChat",
+                .product(
+                    name: "AsyncAlgorithms",
+                    package: "swift-async-algorithms"
+                ),
             ]
         ),
         .executableTarget(
@@ -50,6 +58,10 @@ let package = Package(
                     name: "ArgumentParser",
                     package: "swift-argument-parser"
                 ),
+                .product(
+                    name: "AsyncAlgorithms",
+                    package: "swift-async-algorithms"
+                ),
             ]
         ),
     ]

Sources/AblyChat/BufferingPolicy.swift

@@ -4,4 +4,15 @@ public enum BufferingPolicy: Sendable {
     case unbounded
     case bufferingOldest(Int)
     case bufferingNewest(Int)
+
+    internal func asAsyncStreamBufferingPolicy<T>() -> AsyncStream<T>.Continuation.BufferingPolicy {
+        switch self {
+        case let .bufferingNewest(count):
+            .bufferingNewest(count)
+        case let .bufferingOldest(count):
+            .bufferingOldest(count)
+        case .unbounded:
+            .unbounded
+        }
+    }
 }

Sources/AblyChat/Messages.swift

@@ -54,21 +54,43 @@ public struct QueryOptionsWithoutDirection: Sendable {
 public struct MessageSubscription: Sendable, AsyncSequence {
     public typealias Element = Message
 
-    public init<T: AsyncSequence>(mockAsyncSequence _: T) where T.Element == Element {
-        fatalError("Not yet implemented")
+    private var subscription: Subscription<Element>
+
+    private var mockGetPreviousMessages: (@Sendable (QueryOptionsWithoutDirection) async throws -> any PaginatedResult<Message>)?
+
+    internal init(bufferingPolicy: BufferingPolicy) {
+        subscription = .init(bufferingPolicy: bufferingPolicy)
+    }
+
+    public init<T: AsyncSequence & Sendable>(mockAsyncSequence: T, mockGetPreviousMessages: @escaping @Sendable (QueryOptionsWithoutDirection) async throws -> any PaginatedResult<Message>) where T.Element == Element {
+        subscription = .init(mockAsyncSequence: mockAsyncSequence)
+        self.mockGetPreviousMessages = mockGetPreviousMessages
+    }
+
+    internal func emit(_ element: Element) {
+        subscription.emit(element)
     }
 
-    public func getPreviousMessages(params _: QueryOptionsWithoutDirection) async throws -> any PaginatedResult<Message> {
-        fatalError("Not yet implemented")
+    public func getPreviousMessages(params: QueryOptionsWithoutDirection) async throws -> any PaginatedResult<Message> {
+        guard let mockImplementation = mockGetPreviousMessages else {
+            fatalError("Not yet implemented")
+        }
+        return try await mockImplementation(params)
     }
 
     public struct AsyncIterator: AsyncIteratorProtocol {
+        private var subscriptionIterator: Subscription<Element>.AsyncIterator
+
+        fileprivate init(subscriptionIterator: Subscription<Element>.AsyncIterator) {
+            self.subscriptionIterator = subscriptionIterator
+        }
+
         public mutating func next() async -> Element? {
-            fatalError("Not implemented")
+            await subscriptionIterator.next()
         }
     }
 
     public func makeAsyncIterator() -> AsyncIterator {
-        fatalError("Not implemented")
+        .init(subscriptionIterator: subscription.makeAsyncIterator())
     }
 }