Adds onReceive reducer overloads.

Sources/ComposableSubscriber/ReceiveReducer.swift

@@ -0,0 +1,125 @@
+import ComposableArchitecture
+
+extension Reducer {
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, V>,
+    set setAction: @escaping (inout State, V) -> Void
+  ) -> _ReceiveReducer<Self, V> {
+    .init(
+      parent: self,
+      receiveAction: AnyCasePath(toReceiveAction),
+      setAction: setAction
+    )
+  }
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, V>,
+    set toStateKeyPath: WritableKeyPath<State, V>
+  ) -> _ReceiveReducer<Self, V> {
+    self.onReceive(action: toReceiveAction, set: toStateKeyPath.callAsFunction(root:value:))
+  }
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, V>,
+    set toStateKeyPath: WritableKeyPath<State, V?>
+  ) -> _ReceiveReducer<Self, V> {
+    self.onReceive(action: toReceiveAction, set: toStateKeyPath.callAsFunction(root:value:))
+  }
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, TaskResult<V>>,
+    onSuccess setAction: @escaping (inout State, V) -> Void,
+    onFail: OnFailAction<State>? = nil
+  ) -> _ReceiveReducer<Self, TaskResult<V>> {
+    self.onReceive(action: toReceiveAction) { state, result in
+      switch result {
+      case let .failure(error):
+        if let onFail {
+          onFail(state: &state, error: error)
+        }
+      case let .success(value):
+        setAction(&state, value)
+      }
+    }
+  }
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, TaskResult<V>>,
+    onSuccess toStateKeyPath: WritableKeyPath<State, V>,
+    onFail: OnFailAction<State>? = nil
+  ) -> _ReceiveReducer<Self, TaskResult<V>> {
+    self.onReceive(action: toReceiveAction) { state, result in
+      switch result {
+      case let .failure(error):
+        if let onFail {
+          onFail(state: &state, error: error)
+        }
+      case let .success(value):
+        toStateKeyPath(root: &state, value: value)
+      }
+    }
+  }
+  
+  public func onReceive<V>(
+    action toReceiveAction: CaseKeyPath<Action, TaskResult<V>>,
+    onSuccess toStateKeyPath: WritableKeyPath<State, V?>,
+    onFail: OnFailAction<State>? = nil
+  ) -> _ReceiveReducer<Self, TaskResult<V>> {
+    self.onReceive(action: toReceiveAction) { state, result in
+      switch result {
+      case let .failure(error):
+        if let onFail {
+          onFail(state: &state, error: error)
+        }
+      case let .success(value):
+        toStateKeyPath(root: &state, value: value)
+      }
+    }
+  }
+}
+
+public enum OnFailAction<State> {
+  case xctFail
+  case handle((inout State, Error) -> Void)
+  
+  @usableFromInline
+  func callAsFunction(state: inout State, error: Error) {
+    switch self {
+    case .xctFail:
+      XCTFail("\(error)")
+    case let .handle(handler):
+      handler(&state, error)
+    }
+  }
+}
+
+fileprivate extension WritableKeyPath {
+  
+  func callAsFunction(root: inout Root, value: Value) {
+    root[keyPath: self] = value
+  }
+  
+}
+
+public struct _ReceiveReducer<Parent: Reducer, Value>: Reducer {
+  
+  @usableFromInline
+  let parent: Parent
+  
+  @usableFromInline
+  let receiveAction: AnyCasePath<Parent.Action, Value>
+  
+  @usableFromInline
+  let setAction: (inout Parent.State, Value) -> Void
+    
+  public func reduce(into state: inout Parent.State, action: Parent.Action) -> Effect<Parent.Action> {
+    let baseEffects = parent.reduce(into: &state, action: action)
+    
+    if let value = receiveAction.extract(from: action) {
+      setAction(&state, value)
+    }
+    
+    return baseEffects
+  }
+}

Tests/swift-composable-subscriberTests/swift_composable_subscriberTests.swift

@@ -57,18 +57,12 @@ struct ReducerWithArg {
   @Dependency(\.numberClient) var numberClient
   
   var body: some Reducer<State, Action> {
-    Reduce<State, Action> { state, action in
-      switch action {
-      case let .receive(number):
-        state.currentNumber = number
-        return .none
-      case .task:
-        return .none
-      }
-    }
+
+    EmptyReducer()
+      .onReceive(action: \.receive, set: \.currentNumber)
       .subscribe(
-      using: \.number,
         to: numberClient.numberStreamWithArg, 
+        using: \.number,
         on: \.task,
         with: \.receive
       )
@@ -84,18 +78,11 @@ struct ReducerWithTransform {
   @Dependency(\.numberClient) var numberClient
   
   var body: some Reducer<State, Action> {
-    Reduce<State, Action> { state, action in
-      switch action {
-      case let .receive(number):
-        state.currentNumber = number
-        return .none
-      case .task:
-        return .none
-      }
-    }
+    EmptyReducer()
+      .onReceive(action: \.receive, set: \.currentNumber)
       .subscribe(
-      using: \.number,
         to: numberClient.numberStreamWithArg,
+        using: \.number,
         on: \.task,
         with: \.receive
       ) {