[refactor]: Remove ReactiveSwift from Workflow public interface

BREAKING CHANGE: This changes the public interface of WorkflowHost and WorkflowHostingController.
The rendering property is now a read only property of the Rendering
There is a new renderingPublisher property for a Combine publisher for renderings
The output Signal property has been removed and moved to an extension in WorkflowReactiveSwift
There is a new outputPublisher property for a Combine publisher for output

Author: mjohnson12

Package.swift

@@ -68,9 +68,9 @@ let package = Package(
 
         .target(
             name: "Workflow",
-            dependencies: ["ReactiveSwift"],
             path: "Workflow/Sources"
         ),
+
         .target(
             name: "WorkflowTesting",
             dependencies: [

Samples/Project.swift

@@ -158,7 +158,10 @@ let project = Project(
         .unitTest(
             for: "Workflow",
             sources: "../Workflow/Tests/**",
-            dependencies: [.external(name: "Workflow")]
+            dependencies: [
+                .external(name: "ReactiveSwift"),
+                .external(name: "Workflow"),
+            ]
         ),
         .unitTest(
             for: "WorkflowTesting",

Samples/Tutorial/Frameworks/Tutorial5Complete/Tests/RootWorkflowTests.swift

@@ -87,7 +87,7 @@ class RootWorkflowTests: XCTestCase {
 
         // First rendering is just the welcome screen. Update the name.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(1, backStack.items.count)
 
             guard let welcomeScreen = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {
@@ -100,7 +100,7 @@ class RootWorkflowTests: XCTestCase {
 
         // Log in and go to the todo list.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(1, backStack.items.count)
 
             guard let welcomeScreen = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {
@@ -113,7 +113,7 @@ class RootWorkflowTests: XCTestCase {
 
         // Expect the todo list to be rendered. Edit the first todo.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(2, backStack.items.count)
 
             guard let _ = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {
@@ -134,7 +134,7 @@ class RootWorkflowTests: XCTestCase {
 
         // Selected a todo to edit. Expect the todo edit screen.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(3, backStack.items.count)
 
             guard let _ = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {
@@ -158,7 +158,7 @@ class RootWorkflowTests: XCTestCase {
 
         // Save the selected todo.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(3, backStack.items.count)
 
             guard let _ = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {
@@ -204,7 +204,7 @@ class RootWorkflowTests: XCTestCase {
 
         // Expect the todo list. Validate the title was updated.
         do {
-            let backStack = workflowHost.rendering.value
+            let backStack = workflowHost.rendering
             XCTAssertEqual(2, backStack.items.count)
 
             guard let _ = backStack.items[0].screen.wrappedScreen as? WelcomeScreen else {

Workflow/Sources/WorkflowHost.swift

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import ReactiveSwift
+import Combine
 
 /// Defines a type that receives debug information about a running workflow hierarchy.
 public protocol WorkflowDebugger {
@@ -30,18 +30,30 @@ public protocol WorkflowDebugger {
     func didUpdate(snapshot: WorkflowHierarchyDebugSnapshot, updateInfo: WorkflowUpdateDebugInfo)
 }
 
-/// Manages an active workflow hierarchy.
-public final class WorkflowHost<WorkflowType: Workflow> {
-    private let (outputEvent, outputEventObserver) = Signal<WorkflowType.Output, Never>.pipe()
+public protocol WorkflowOutputPublisher {
+    associatedtype Output
+
+    var outputPublisher: AnyPublisher<Output, Never> { get }
+}
 
+/// Manages an active workflow hierarchy.
+public final class WorkflowHost<WorkflowType: Workflow>: WorkflowOutputPublisher {
     // @testable
     let rootNode: WorkflowNode<WorkflowType>
 
-    private let mutableRendering: MutableProperty<WorkflowType.Rendering>
+    private let renderingSubject: CurrentValueSubject<WorkflowType.Rendering, Never>
+    private let outputSubject = PassthroughSubject<WorkflowType.Output, Never>()
 
     /// Represents the `Rendering` produced by the root workflow in the hierarchy. New `Rendering` values are produced
     /// as state transitions occur within the hierarchy.
-    public let rendering: Property<WorkflowType.Rendering>
+    public var rendering: WorkflowType.Rendering {
+        renderingSubject.value
+    }
+
+    /// A Publisher containing rendering events produced by the root workflow in the hierarchy.
+    public var renderingPublisher: AnyPublisher<WorkflowType.Rendering, Never> {
+        renderingSubject.eraseToAnyPublisher()
+    }
 
     /// Context object to pass down to descendant nodes in the tree.
     let context: HostContext
@@ -78,8 +90,8 @@ public final class WorkflowHost<WorkflowType: Workflow> {
             parentSession: nil
         )
 
-        self.mutableRendering = MutableProperty(rootNode.render())
-        self.rendering = Property(mutableRendering)
+        self.renderingSubject = CurrentValueSubject(rootNode.render())
+
         rootNode.enableEvents()
 
         debugger?.didEnterInitialState(snapshot: rootNode.makeDebugSnapshot())
@@ -110,12 +122,12 @@ public final class WorkflowHost<WorkflowType: Workflow> {
     private func handle(output: WorkflowNode<WorkflowType>.Output) {
         let shouldRender = !shouldSkipRenderForOutput(output)
         if shouldRender {
-            mutableRendering.value = rootNode.render()
+            renderingSubject.send(rootNode.render())
         }
 
         // Always emit an output, regardless of whether a render occurs
         if let outputEvent = output.outputEvent {
-            outputEventObserver.send(value: outputEvent)
+            outputSubject.send(outputEvent)
         }
 
         debugger?.didUpdate(
@@ -129,9 +141,9 @@ public final class WorkflowHost<WorkflowType: Workflow> {
         }
     }
 
-    /// A signal containing output events emitted by the root workflow in the hierarchy.
-    public var output: Signal<WorkflowType.Output, Never> {
-        outputEvent
+    /// A publisher containing output events emitted by the root workflow in the hierarchy.
+    public var outputPublisher: AnyPublisher<WorkflowType.Output, Never> {
+        outputSubject.eraseToAnyPublisher()
     }
 }
 

Workflow/Tests/AnyWorkflowTests.swift

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import ReactiveSwift
+import Combine
 import XCTest
 @testable import Workflow
 
@@ -40,19 +40,21 @@ public class AnyWorkflowTests: XCTestCase {
         let host = WorkflowHost(workflow: OnOutputWorkflow())
 
         let renderingExpectation = expectation(description: "Waiting for rendering")
-        host.rendering.producer.startWithValues { rendering in
+        let cancellable = host.renderingPublisher.sink { rendering in
             if rendering {
                 renderingExpectation.fulfill()
             }
         }
 
         let outputExpectation = expectation(description: "Waiting for output")
-        host.output.observeValues { output in
+        let outputCancellable = host.outputPublisher.sink { output in
             if output {
                 outputExpectation.fulfill()
             }
         }
         wait(for: [renderingExpectation, outputExpectation], timeout: 1)
+        cancellable.cancel()
+        outputCancellable.cancel()
     }
 
     func testOnlyWrapsOnce() {