Econa77 · Feb 24, 2021 · Dec 31, 2020 · Dec 31, 2020 · Dec 31, 2020 · Dec 31, 2020
diff --git a/APIKit.xcodeproj/project.pbxproj b/APIKit.xcodeproj/project.pbxproj
@@ -7,6 +7,8 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		0969AE0F259DEC6D00C498AF /* Combine.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0969AE0E259DEC6D00C498AF /* Combine.swift */; };
+		0973EE35259E2DDC00879BA2 /* CombineTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0973EE34259E2DDC00879BA2 /* CombineTests.swift */; };
 		7F698E501D9D680C00F1561D /* FormURLEncodedBodyParametersTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7F698E3C1D9D680C00F1561D /* FormURLEncodedBodyParametersTests.swift */; };
 		7F698E511D9D680C00F1561D /* JSONBodyParametersTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7F698E3D1D9D680C00F1561D /* JSONBodyParametersTests.swift */; };
 		7F698E521D9D680C00F1561D /* MultipartFormDataParametersTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7F698E3E1D9D680C00F1561D /* MultipartFormDataParametersTests.swift */; };
@@ -76,6 +78,8 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		0969AE0E259DEC6D00C498AF /* Combine.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Combine.swift; sourceTree = "<group>"; };
+		0973EE34259E2DDC00879BA2 /* CombineTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CombineTests.swift; sourceTree = "<group>"; };
 		141F120F1C1C96820026D415 /* Base.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Base.xcconfig; path = Configurations/Base.xcconfig; sourceTree = "<group>"; };
 		141F12101C1C96820026D415 /* Debug.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Debug.xcconfig; path = Configurations/Debug.xcconfig; sourceTree = "<group>"; };
 		141F12111C1C96820026D415 /* Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Release.xcconfig; path = Configurations/Release.xcconfig; sourceTree = "<group>"; };
@@ -149,6 +153,23 @@
 /* End PBXFrameworksBuildPhase section */
 
 /* Begin PBXGroup section */
+		0969AE0D259DEC3C00C498AF /* Combine */ = {
+			isa = PBXGroup;
+			children = (
+				0969AE0E259DEC6D00C498AF /* Combine.swift */,
+			);
+			name = Combine;
+			path = APIKit/Combine;
+			sourceTree = "<group>";
+		};
+		0973EE33259E2DD000879BA2 /* Combine */ = {
+			isa = PBXGroup;
+			children = (
+				0973EE34259E2DDC00879BA2 /* CombineTests.swift */,
+			);
+			path = Combine;
+			sourceTree = "<group>";
+		};
 		141F120E1C1C96690026D415 /* Configurations */ = {
 			isa = PBXGroup;
 			children = (
@@ -219,6 +240,7 @@
 				7F698E451D9D680C00F1561D /* RequestTests.swift */,
 				7F698E491D9D680C00F1561D /* SessionCallbackQueueTests.swift */,
 				7F698E4A1D9D680C00F1561D /* SessionTests.swift */,
+				0973EE33259E2DD000879BA2 /* Combine */,
 				7F698E3B1D9D680C00F1561D /* BodyParametersType */,
 				7F698E401D9D680C00F1561D /* DataParserType */,
 				7F698E461D9D680C00F1561D /* SessionAdapterType */,
@@ -288,6 +310,7 @@
 				7F7048CA1D9D89BE003C99F6 /* Request.swift */,
 				7F7048CB1D9D89BE003C99F6 /* Session.swift */,
 				7F7048CC1D9D89BE003C99F6 /* Unavailable.swift */,
+				0969AE0D259DEC3C00C498AF /* Combine */,
 				7F85FB8B1C9D317300CEE132 /* SessionAdapter */,
 				7F18BD0D1C972C38003A31DF /* BodyParameters */,
 				7FA19A441C9CC9A2005D25AE /* DataParser */,
@@ -473,6 +496,7 @@
 				ECA831481DE4DDBF004EB1B5 /* ProtobufDataParser.swift in Sources */,
 				7F7048F31D9D8A1F003C99F6 /* URLEncodedSerialization.swift in Sources */,
 				7F7048D71D9D89F2003C99F6 /* URLSessionAdapter.swift in Sources */,
+				0969AE0F259DEC6D00C498AF /* Combine.swift in Sources */,
 				7F7048EB1D9D8A08003C99F6 /* StringDataParser.swift in Sources */,
 				7F7048CF1D9D89BE003C99F6 /* HTTPMethod.swift in Sources */,
 			);
@@ -490,6 +514,7 @@
 				ECA8314A1DE4DEBE004EB1B5 /* ProtobufDataParserTests.swift in Sources */,
 				7F698E5E1D9D680C00F1561D /* TestRequest.swift in Sources */,
 				7F698E601D9D680C00F1561D /* TestSessionTask.swift in Sources */,
+				0973EE35259E2DDC00879BA2 /* CombineTests.swift in Sources */,
 				7FA1690D1D9D8C80006C982B /* HTTPStub.swift in Sources */,
 				7F698E5A1D9D680C00F1561D /* URLSessionAdapterTests.swift in Sources */,
 				7F698E561D9D680C00F1561D /* StringDataParserTests.swift in Sources */,

diff --git a/Sources/APIKit/Combine/Combine.swift b/Sources/APIKit/Combine/Combine.swift
@@ -0,0 +1,89 @@
+#if canImport(Combine)
+
+import Foundation
+import Combine
+
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+public struct SessionTaskPublisher<Request: APIKit.Request>: Publisher {
+    /// The kind of values published by this publisher.
+    public typealias Output = Request.Response
+
+    /// The kind of errors this publisher might publish.
+    public typealias Failure = SessionTaskError
+
+    private let request: Request
+    private let session: Session
+    private let callbackQueue: CallbackQueue?
+
+    public init(request: Request, session: Session, callbackQueue: CallbackQueue?) {
+        self.request = request
+        self.session = session
+        self.callbackQueue = callbackQueue
+    }
+
+    public func receive<S>(subscriber: S) where S: Subscriber, S.Failure == SessionTaskPublisher.Failure, S.Input == SessionTaskPublisher.Output {
+        subscriber.receive(subscription: SessionTaskSubscription(request: request,
+                                                                 session: session,
+                                                                 callbackQueue: callbackQueue,
+                                                                 downstream: subscriber))
+    }
+
+    private final class SessionTaskSubscription<Request: APIKit.Request, Downstream: Subscriber>: Subscription where Request.Response == Downstream.Input, Downstream.Failure == Failure {
+
+        private let request: Request
+        private let session: Session
+        private let callbackQueue: CallbackQueue?
+        private var downstream: Downstream?
+        private var task: SessionTask?
+
+        init(request: Request, session: Session, callbackQueue: CallbackQueue?, downstream: Downstream) {
+            self.request = request
+            self.session = session
+            self.callbackQueue = callbackQueue
+            self.downstream = downstream
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            assert(demand > 0)
+            guard let downstream = self.downstream else { return }
+            self.downstream = nil
+            task = session.send(request, callbackQueue: callbackQueue) { result in
+                switch result {
+                case .success(let response):
+                    _ = downstream.receive(response)
+                    downstream.receive(completion: .finished)
+                case .failure(let error):
+                    downstream.receive(completion: .failure(error))
+                }
+            }
+        }
+
+        func cancel() {
+            task?.cancel()
+            downstream = nil
+        }
+    }
+}
+
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+public extension Session {
+    /// Calls `sessionTaskPublisher(for:callbackQueue:)` of `Session.shared`.
+    /// - parameter request: The request to be sent.
+    /// - parameter callbackQueue: The queue where the handler runs. If this parameters is `nil`, default `callbackQueue` of `Session` will be used.
+    /// - returns: A publisher that wraps a session task for the request.
+    static func sessionTaskPublisher<Request: APIKit.Request>(for request: Request, callbackQueue: CallbackQueue? = nil) -> SessionTaskPublisher<Request> {
+        return SessionTaskPublisher(request: request, session: .shared, callbackQueue: callbackQueue)
+    }
+
+    /// Returns a publisher that wraps a session task for the request.
+    ///
+    /// The publisher publishes `Request.Response` when the task completes, or terminates if the task fails with an error.
+    /// - parameter request: The request to be sent.
+    /// - parameter callbackQueue: The queue where the handler runs. If this parameters is `nil`, default `callbackQueue` of `Session` will be used.
+    /// - returns: A publisher that wraps a session task for the request.
+    func sessionTaskPublisher<Request: APIKit.Request>(for request: Request, callbackQueue: CallbackQueue? = nil) -> SessionTaskPublisher<Request> {
+        return SessionTaskPublisher(request: request, session: self, callbackQueue: callbackQueue)
+    }
+}
+
+#endif
diff --git a/Sources/APIKit/Session.swift b/Sources/APIKit/Session.swift
@@ -30,7 +30,7 @@ open class Session {
         return privateShared
     }
 
-    /// Calls `send(_:handler:)` of `sharedSession`.
+    /// Calls `send(_:callbackQueue:handler:)` of `Session.shared`.
     /// - parameter request: The request to be sent.
     /// - parameter callbackQueue: The queue where the handler runs. If this parameters is `nil`, default `callbackQueue` of `Session` will be used.
     /// - parameter handler: The closure that receives result of the request.
@@ -40,7 +40,7 @@ open class Session {
         return shared.send(request, callbackQueue: callbackQueue, handler: handler)
     }
 
-    /// Calls `cancelRequests(with:passingTest:)` of `sharedSession`.
+    /// Calls `cancelRequests(with:passingTest:)` of `Session.shared`.
     open class func cancelRequests<Request: APIKit.Request>(with requestType: Request.Type, passingTest test: @escaping (Request) -> Bool = { _ in true }) {
         shared.cancelRequests(with: requestType, passingTest: test)
     }

diff --git a/Tests/APIKitTests/Combine/CombineTests.swift b/Tests/APIKitTests/Combine/CombineTests.swift
@@ -0,0 +1,124 @@
+#if canImport(Combine)
+
+import Foundation
+import XCTest
+import Combine
+import APIKit
+
+@available(macOS 10.15, iOS 13, watchOS 6, tvOS 13, *)
+final class CombineTests: XCTestCase {
+
+    var adapter: TestSessionAdapter!
+    var session: Session!
+    var cancellables: Set<AnyCancellable> = []
+
+    override func setUp() {
+        super.setUp()
+        adapter = TestSessionAdapter()
+        session = Session(adapter: adapter)
+    }
+
+    override func tearDown() {
+        super.tearDown()
+        cancellables = []
+    }
+
+    func testSuccess() {
+        let dictionary = ["key": "value"]
+        adapter.data = try! JSONSerialization.data(withJSONObject: dictionary, options: [])
+
+        let expectation = self.expectation(description: "wait for response")
+        let request = TestRequest()
+
+        session.sessionTaskPublisher(for: request)
+            .sink(receiveCompletion: { completion in
+                switch completion {
+                case .failure:
+                    XCTFail()
+                case .finished:
+                    expectation.fulfill()
+                }
+            }, receiveValue: { response in
+                XCTAssertEqual((response as? [String: String])?["key"], "value")
+            })
+            .store(in: &cancellables)
+
+        waitForExpectations(timeout: 1.0, handler: nil)
+    }
+
+    func testParseDataError() {
+        adapter.data = "{\"broken\": \"json}".data(using: .utf8, allowLossyConversion: false)
+
+        let expectation = self.expectation(description: "wait for response")
+        let request = TestRequest()
+
+        session.sessionTaskPublisher(for: request)
+            .sink(receiveCompletion: { completion in
+                if case .failure(let error) = completion, case .responseError(let responseError as NSError) = error {
+                    XCTAssertEqual(responseError.domain, NSCocoaErrorDomain)
+                    XCTAssertEqual(responseError.code, 3840)
+                    expectation.fulfill()
+                } else {
+                    XCTFail()
+                }
+            }, receiveValue: { response in
+                XCTFail()
+            })
+            .store(in: &cancellables)
+
+        waitForExpectations(timeout: 1.0, handler: nil)
+    }
+
+    func testBefore2020OSVersionsCancel() throws {
+        if #available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
+            throw XCTSkip("Skip on After 2020 OS versions, as Combine cancellation no longer emits a value.")
+        }
+
+        let cancelExpectation = self.expectation(description: "wait for cancel")
+        let completionExpectation = self.expectation(description: "wait for response")
+        let request = TestRequest()
+
+        let cancellable = session.sessionTaskPublisher(for: request)
+            .handleEvents(receiveCancel: {
+                cancelExpectation.fulfill()
+            })
+            .sink(receiveCompletion: { completion in
+                if case .failure(let error) = completion, case .connectionError(let connectionError as NSError) = error {
+                    XCTAssertEqual(connectionError.code, 0)
+                    completionExpectation.fulfill()
+                } else {
+                    XCTFail()
+                }
+            }, receiveValue: { response in
+                XCTFail()
+            })
+        cancellable.cancel()
+
+        waitForExpectations(timeout: 1.0, handler: nil)
+    }
+
+    func testAfter2020OSVersionsCancel() throws {
+        guard #available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *) else {
+            throw XCTSkip("Skip on Before 2020 OS versions.")
+        }
+
+        let expectation = self.expectation(description: "wait for cancel")
+        let request = TestRequest()
+
+        let cancellable = session.sessionTaskPublisher(for: request)
+            .handleEvents(receiveCancel: {
+                expectation.fulfill()
+            })
+            .sink(receiveCompletion: { completion in
+                XCTFail()
+            }, receiveValue: { response in
+                XCTFail()
+            })
+        cancellable.cancel()
+
+        waitForExpectations(timeout: 1.0, handler: nil)
+    }
+
+}
+
+#endif