[APP-2869] Add Combine and SwiftUI bridges (#125)

Author: moglistree

.circleci/config.yml

@@ -4,12 +4,12 @@
 version: 2.1
 
 anchors:
-  - &test_device "iPhone Xs"
+  - &test_device "iPhone 14"
+  - &test_device_os "16.2"
   - &clean_before_build true
-  - &test_output_folder test_output
   - &default_executor
     macos:
-      xcode: "14.0.0"
+      xcode: "14.2.0"
 
 env:
   global:
@@ -36,11 +36,18 @@ commands:
             pod install --verbose
 
   test_main_project:
+    parameters:
+        simulator:
+          type: string
+          default: *test_device
+        os_version:
+          type: string
+          default: *test_device_os
     steps:
       - checkout
       - test_project_and_store_results:
-          project: "Flow.xcodeproj"
-          scheme: "Flow"
+          simulator: <<parameters.simulator>>
+          os_version: <<parameters.os_version>>
 
   test_example_project:
     parameters:
@@ -54,30 +61,32 @@ commands:
           workspace: "Example.xcworkspace"
           scheme: "Example"
           path: <<parameters.path>>
-          test_output_folder: *test_output_folder
 
   # We introduced two separate commands for projects and workspaces because we didn't find a generic and non-confusing way to introduce
-  # a condition to only pass either the project or the workspace environment argument to the fastlane scan
+  # a condition to only pass either the project or the workspace environment argument to the test output
   test_project_and_store_results:
     description: "Builds and tests a project and then stores the results of the tests as artifacts and test results report"
     parameters:
-      project:
+      simulator:
         type: string
-      scheme:
+        default: *test_device
+      os_version:
         type: string
+        default: *test_device_os
     steps:
       - run:
-          command: fastlane scan
-          environment:
-              SCAN_PROJECT: <<parameters.project>>
-              SCAN_SCHEME: <<parameters.scheme>>
-              SCAN_DEVICE: *test_device
-              SCAN_CLEAN: *clean_before_build
+          name: Run tests on iOS <<parameters.os_version>>
+          command: |
+            xcodebuild -scheme Flow \
+            -project Flow.xcodeproj \
+            -destination "platform=iOS Simulator,OS=<<parameters.os_version>>,name=<<parameters.simulator>>" \
+             build test \
+             | xcpretty --report junit --output 'test_output/report.junit'
       - store_artifacts: # This will by default store an html and junit file as artifacts (See "Artifacts" tab in CircleCI report)
-          path: *test_output_folder # test_output is the default temporary folder for fastlane scan output
-          destination: *test_output_folder # This will create a sub structure in the artifacts section in CircleCI
+          path: test_output # test_output is the default temporary folder for test output
+          destination: test_output # This will create a sub structure in the artifacts section in CircleCI
       - store_test_results: # This will store the test results so you can then see them in the "Test Summary" tab in CircleCI report
-          path: *test_output_folder
+          path: test_output
 
   test_workspace_and_store_results:
     description: "Builds and tests a workspace and then stores the results of the tests as artifacts and test results report"
@@ -88,23 +97,27 @@ commands:
         type: string
       path:
         type: string
-      test_output_folder:
+      simulator:
         type: string
+        default: *test_device
+      os_version:
+        type: string
+        default: *test_device_os
     steps:
       - run:
-          command:  |
+          name: Run examples
+          command: |
             cd <<parameters.path>>
-            fastlane scan
-          environment:
-              SCAN_WORKSPACE: <<parameters.workspace>>
-              SCAN_SCHEME: <<parameters.scheme>>
-              SCAN_DEVICE: *test_device
-              SCAN_CLEAN: *clean_before_build
+            xcodebuild -workspace <<parameters.workspace>> \
+            -scheme <<parameters.scheme>> \
+            -destination "platform=iOS Simulator,OS=<<parameters.os_version>>,name=<<parameters.simulator>>" \
+             build test \
+             | xcpretty --report junit --output 'test_output/report.junit'
       - store_artifacts: # This will by default store an html and junit file as artifacts (See "Artifacts" tab in CircleCI report)
-          path: <<parameters.path>>/<<parameters.test_output_folder>> # test_output is the default temporary folder for fastlane scan output
-          destination: <<parameters.test_output_folder>> # This will create a sub structure in the artifacts section in CircleCI
+          path: <<parameters.path>>/test_output # test_output is the default temporary folder for test output
+          destination: test_output # This will create a sub structure in the artifacts section in CircleCI
       - store_test_results: # This will store the test results so you can then see them in the "Test Summary" tab in CircleCI report
-          path: <<parameters.path>>/<<parameters.test_output_folder>>
+          path: <<parameters.path>>/test_output
 
 jobs:
   swiftlint:
@@ -136,7 +149,9 @@ jobs:
     macos:
       xcode: "13.0.0"
     steps:
-      - test_main_project
+      - test_main_project:
+          simulator: "iPhone 13"
+          os_version: "15.0"
 
   test-xcode14-ios16:
     <<: *default_executor

Bridges/CancelBag.swift

@@ -0,0 +1,63 @@
+//
+//  CancelBag.swift
+//  Flow
+//
+//  Created by Carl Ekman on 2023-02-09.
+//  Copyright © 2023 PayPal Inc. All rights reserved.
+//
+
+import Foundation
+#if canImport(Combine)
+import Combine
+
+/// A type alias for `Set<AnyCancellable>` meant to bridge some of the patterns of `DisposeBag`
+/// with modern conventions, like `store(in set: inout Set<AnyCancellable>)`.
+@available(iOS 13.0, macOS 10.15, *)
+public typealias CancelBag = Set<AnyCancellable>
+
+@available(iOS 13.0, macOS 10.15, *)
+extension CancelBag: Cancellable {
+    /// Cancel all elements in the set.
+    public func cancel() {
+        forEach { $0.cancel() }
+    }
+
+    /// Cancel all elements and then empty the set.
+    public mutating func empty() {
+        cancel()
+        removeAll()
+    }
+
+    /// Create a new, empty set, which is itself a part of self.
+    /// Corresponds to `innerBag()` for `DisposeBag`.
+    public mutating func subset() -> CancelBag {
+        let bag = CancelBag()
+        self.insert(AnyCancellable(bag))
+        return bag
+    }
+}
+
+@available(iOS 13.0, macOS 10.15, *)
+extension CancelBag {
+    public init(disposable: Disposable) {
+        self.init([disposable.asAnyCancellable])
+    }
+
+    public var asAnyCancellable: AnyCancellable {
+        AnyCancellable(self)
+    }
+}
+
+@available(iOS 13.0, macOS 10.15, *)
+public func += (cancelBag: inout CancelBag, cancellable: AnyCancellable?) {
+    if let cancellable = cancellable {
+        cancelBag.insert(cancellable)
+    }
+}
+
+@available(iOS 13.0, macOS 10.15, *)
+public func += (cancelBag: inout CancelBag, cancellation: @escaping () -> Void) {
+    cancelBag.insert(AnyCancellable(cancellation))
+}
+
+#endif

Bridges/Disposable+Cancellable.swift

@@ -0,0 +1,27 @@
+//
+//  Disposable+Cancellable.swift
+//  Flow
+//
+//  Created by Carl Ekman on 2023-02-09.
+//  Copyright © 2023 PayPal Inc. All rights reserved.
+//
+
+import Foundation
+#if canImport(Combine)
+import Combine
+
+@available(iOS 13.0, macOS 10.15, *)
+extension Disposable {
+    public var asAnyCancellable: AnyCancellable {
+        AnyCancellable { self.dispose() }
+    }
+}
+
+@available(iOS 13.0, macOS 10.15, *)
+extension Future {
+    public var cancellable: AnyCancellable {
+        AnyCancellable { self.disposable.dispose() }
+    }
+}
+
+#endif

Bridges/Future+Combine.swift

@@ -0,0 +1,20 @@
+//
+// Copyright © 2023 PayPal Inc. All rights reserved.
+//
+
+import Foundation
+#if canImport(Combine)
+import Combine
+
+@available(iOS 13.0, macOS 10.15, *)
+extension Flow.Future {
+    /// Convert a `Flow.Future<Value>` to a `Combine.Future<Value, Error>` intended to be
+    /// used to bridge between the `Flow` and `Combine` world
+    public var toCombineFuture: Combine.Future<Value, Error> {
+        Combine.Future { promise in
+            self.onResult { promise($0) }
+        }
+    }
+}
+
+#endif

Bridges/Publisher+Utilities.swift

@@ -0,0 +1,59 @@
+//
+//  Callbacker+Combine.swift
+//  Flow
+//
+//  Created by Carl Ekman on 2023-02-09.
+//  Copyright © 2023 PayPal Inc. All rights reserved.
+//
+
+import Foundation
+#if canImport(Combine)
+import Combine
+
+@available(iOS 13.0, macOS 10.15, *)
+public extension Publisher {
+    /// Performs just link `sink(receiveValue:)`, but the cancellable produced from each received value
+    /// will be automatically cancelled once a new value is published. Completion will cancel the last cancellable as well.
+    ///
+    /// - Intended to be used similarly to `onValueDisposePrevious(_:on:)`.
+    func autosink(
+        receiveCompletion: @escaping ((Subscribers.Completion<Self.Failure>) -> Void),
+        receiveValue: @escaping ((Self.Output) -> AnyCancellable)
+    ) -> AnyCancellable {
+        var bag = CancelBag()
+        var subBag = bag.subset()
+
+        bag += sink(receiveCompletion: { completion in
+            subBag.cancel()
+            receiveCompletion(completion)
+        }, receiveValue: { value in
+            subBag.cancel()
+            subBag += receiveValue(value)
+        })
+
+        return bag.asAnyCancellable
+    }
+}
+
+@available(iOS 13.0, macOS 10.15, *)
+public extension Publisher where Self.Failure == Never {
+    /// Performs just link `sink(receiveValue:)`, but the cancellable produced from each received value
+    /// will be automatically cancelled once a new value is published, for publishers that never fail.
+    ///
+    /// - Intended to be used similarly to `onValueDisposePrevious(_:on:)`.
+    func autosink(
+        receiveValue: @escaping ((Self.Output) -> AnyCancellable)
+    ) -> AnyCancellable {
+        var bag = CancelBag()
+        var subBag = bag.subset()
+
+        bag += sink { value in
+            subBag.cancel()
+            subBag += receiveValue(value)
+        }
+
+        return bag.asAnyCancellable
+    }
+}
+
+#endif

Bridges/Signal+Combine.swift

@@ -0,0 +1,91 @@
+//
+// Copyright © 2023 PayPal Inc. All rights reserved.
+//
+
+import Foundation
+#if canImport(Combine)
+import Combine
+
+extension CoreSignal {
+    @available(iOS 13.0, macOS 10.15, *)
+    final class SignalPublisher: Publisher, Cancellable {
+        typealias Output = Value
+        typealias Failure = Error
+        
+        internal var signal: CoreSignal<Kind, Value>
+        internal var bag: CancelBag
+
+        init(signal: CoreSignal<Kind, Value>) {
+            self.signal = signal
+            self.bag = []
+        }
+
+        func receive<S>(
+            subscriber: S
+        ) where S : Subscriber, Failure == S.Failure, Value == S.Input {
+            // Creating our custom subscription instance:
+            let subscription = EventSubscription<S>()
+            subscription.target = subscriber
+
+            // Attaching our subscription to the subscriber:
+            subscriber.receive(subscription: subscription)
+
+            // Collect cancellables when attaching to signal
+            bag += signal
+                .onValue { subscription.trigger(for: $0) }
+                .asAnyCancellable
+
+            if let finiteVersion = signal as? FiniteSignal<Value> {
+                bag += finiteVersion.onEvent { event in
+                    if case let .end(error) = event {
+                        if let error = error {
+                            subscription.end(with: error)
+                        } else {
+                            subscription.end()
+                        }
+                    }
+                }.asAnyCancellable
+            }
+        }
+
+        func cancel() {
+            bag.cancel()
+        }
+
+        deinit {
+            cancel()
+        }
+    }
+    
+    @available(iOS 13.0, macOS 10.15, *)
+    final class EventSubscription<Target: Subscriber>: Subscription
+        where Target.Input == Value {
+        
+        var target: Target?
+
+        func request(_ demand: Subscribers.Demand) {}
+
+        func cancel() {
+            target = nil
+        }
+
+        func end(with error: Target.Failure? = nil) {
+            if let error = error {
+                _ = target?.receive(completion: .failure(error))
+            } else {
+                _ = target?.receive(completion: .finished)
+            }
+        }
+        
+        func trigger(for value: Value) {
+            _ = target?.receive(value)
+        }
+    }
+    
+    @available(iOS 13.0, macOS 10.15, *)
+    public var asAnyPublisher: AnyPublisher<Value, Error> {
+        SignalPublisher(signal: self).eraseToAnyPublisher()
+    }
+}
+
+#endif